End criteria for reaching maximal oxygen uptake must be strict and adjusted to sex and age: a cross-sectional study

Limb-specific blood flow regulation during cycling exercise in traumatic single lower limb amputees

PURPOSE

To investigate the limb-specific blood flow regulation during dynamic bilateral cycling exercise in individuals with traumatic single lower-limb amputation compared to a control group.

METHODS

Seven individuals with single lower leg amputation (AMP) (37 ± 11 years, 11 ± 8 years since amputation) and 7 age-matched controls (Ctrl) (36 ± 10 years) were tested during three 5 min constant workload exercise at 60W, 100W, and 80% of peak power output (PPO), on a reclined cycling ergometer. In AMP, femoral blood flow (FBF) and leg vascular conductance (LVC) were measured in the amputated leg (AL) and whole leg (WL), while in Ctrl, the same measurements were obtained in the right and left legs. Interlimb balance was measured with a power meter, and bilateral asymmetry index was calculated for FBF and interlimb balance. Oxygen consumption ( V ˙ O2), ventilation (V ˙ E ), mean arterial pressure (MAP), heart rate (HR), and cardiac output (CO) were also quantified.

RESULTS

AMP exhibited lower FBF in AL compared to WL (60W, - 61%; 100W, -69%; 80% PPO, - 64%; p < 0.001). LVC increased as expected in WL but did not increase significantly throughout workloads in AL. Interlimb balance exhibited a much higher contribution of the WL (60W, 76% of the work; 100W, 68%; 80% PPO,65%) than AL (60W, 26%; 100W, 34%; 80% PPO, 35%). No differences were found in FBF (p = 0.187), LVC (p = 0.871), and interlimb balance (p = 0.829) in CTRLs. No difference between AMP and CTRL in V O2 (p = 0.241),V ˙ E (p = 0.124), MAP (p = 0.186), HR (p = 0.360), and CO (p = 0.144) at any workload was detected.

CONCLUSION

Individuals with amputation present considerable limb-specific blood flow regulation during bilateral cycling exercise. Understanding the mechanisms for this interlimb difference may provide important information to improve rehabilitation and training in this population.

Cardiopulmonary exercise tests in people with chronic stroke: Interpretation and clinical application

OBJECTIVE

To understand in people with stroke: (1) reasons for cardiopulmonary treadmill exercise test termination, (2) how frequently secondary criteria indicating a maximal test are met, and (3) how test termination is related to volume of oxygen consumption and participant characteristics.

DESIGN

A secondary analysis from the Promoting Recovery Optimization of Walking Activity in Stroke (NCT02835313) clinical trial.

SETTING

Four outpatient rehabilitation clinics.

PARTICIPANTS

People with chronic stroke able to walk without assistance of another person.

INTERVENTION

Participants (n = 250) randomized in a larger clinical trial completed symptom limited graded exercise treadmill tests pre- (n = 247) and post-intervention (n = 185). Treadmill exercise tests were conducted at constant speed with incremental incline increases.

MAIN MEASURES

The primary measure was reason for cardiopulmonary exercise test termination. Secondary measures included: oxygen consumption, ventilatory threshold, peak heart rate, respiratory exchange ratio, six-minute walk test, and fastest walking speed.

RESULTS

There were six categories of test termination, electrocardiogram (11%), blood pressure/heart rate (13%), biomechanical (25%), self-selected (41%), equipment malfunction (8%), and other (2%). Only 1.9% of tests achieved the threshold to confirm a maximal aerobic effort. There were no differences in peak volume of oxygen consumption or participant characteristics between test termination categories.

CONCLUSIONS

Analyses indicate few with chronic stroke exhibit a maximal aerobic effort on a cardiopulmonary exercise test. If the cardiorespiratory system is not thoroughly taxed during treadmill exercise tests in people with chronic stroke, interpreting results as their cardiorespiratory fitness should be done cautiously.

Effects of exercise and exercise timing on energy intake and appetite control in Danish individuals with overweight or obesity with and without type 2 diabetes: a protocol for a randomised controlled cross-over trial

INTRODUCTION

The aim of this study is to investigate the effects of acute exercise on appetite control and whether this differs between morning and late afternoon in individuals with overweight/obesity with or without type 2 diabetes (T2D).

METHODS AND ANALYSIS

The hedonic and homeostatic appetite control in obesity and type 2 diabetes in the context of meal and exercise timing (TIMEX) study is a randomised, controlled, cross-over trial. Fifty-eight women and men (aged 18-75 years) with overweight or obesity (body mass index ≥25 kg/m2) with or without T2D will be recruited. All participants will complete a screening and baseline visit followed by four test visits: two morning visits and two late afternoon visits. The participants will arrive in the fasted state during the visits. During one morning visit and one late afternoon visit, the participants will engage in a 45-min bout of acute high-intensity interval exercise on an ergometer bicycle. The remaining two visits (one morning and one late afternoon visit) will include 45 min of rest. Fifteen minutes after the rest or exercise period, the participants will be presented with an ad libitum meal. Blood samples will be collected and subjective appetite will be assessed using Visual Analogue Scales in the fasted state before exercise/rest, immediately post-exercise/rest and at 15, 30, 45 and 60 min post-exercise/rest. Food reward and food preferences will be assessed using the validated diurnal version of the Steno Biometric Food Preference Task in the fasted state before exercise/rest and 15 min after the ad libitum meal (45 min post-exercise/rest). The primary outcome is the difference in ad libitum energy intake after exercise compared with rest. Secondary outcomes include eating rate; 24-hour energy intake; appetite-related metabolites and hormones, and circulating biomarkers assessed from proteomics, metabolomics and lipidomics analyses; food choice, food attention and reaction time, explicit and implicit liking and wanting for different food categories, subjective appetite; ratings of perceived exertion during exercise. All outcomes will be compared between morning and late afternoon and between participants with and without T2D.

ETHICS AND DISSEMINATION

The study has been approved by the Ethics Committee of the Capital Region of Denmark (H-22019913) and the Capital Region of Denmark's Research Register (Privacy). The study will be conducted in accordance with the Declaration of Helsinki. All results will be published in national and international peer-reviewed journals and will be disseminated at national and international conferences.

TRIAL REGISTRATION NUMBER

NCT05768958.

Walking Economy and Preferred Speed in Old and Very Old Men

PURPOSE

With aging, the decline in preferred walking speed (PWS), influenced by the increased energy cost of walking (CoW), is a key predictor of morbidity. However, the determinants associated with PWS and CoW remain poorly understood, especially after 80 yr old. The aim of the study was to characterize the amplitude and mechanisms of age-related decline in CoW and PWS in old (OM) and very old (VOM) men.

METHODS

Thirty-nine young men (YM; 22.1 ± 3.4 yr), 34 OM (71.7 ± 4.1 yr), and 23 VOM (85.8 ± 2.7 yr) performed aerobic, neuromuscular, and gait assessments. Net CoW was measured on a treadmill. Physical activity (PA) was evaluated by questionnaire and accelerometry.

RESULTS

Net CoW was 32% ( P < 0.001), 19% ( P < 0.01), and 26% ( P < 0.001) higher in VOM compared with OM for 1.11 m·s -1 , 1.67 m·s -1 , and PWS. Net CoW was also 27% ( P < 0.001), 26% ( P < 0.01), and 29% ( P < 0.001) higher in OM compared with YM at these speeds. Linear regression stratified by age showed that net CoW at PWS was associated with step frequency ( r = 0.79; P < 0.001) for OM and with both coefficient of variation of stride mean time ( r = 0.48; P < 0.05) and maximal strength of knee extensors ( r = -0.54; P < 0.05) for VOM. The same analysis revealed that PWS was correlated with net CoW ( r = -0.56; P < 0.05) and PA ( r = 0.47; P < 0.05) in VOM.

CONCLUSIONS

The progressive increase in net CoW with age was associated with gait and neuromuscular impairments, particularly after the age of 80 yr. This increase in net CoW was related to a decrease in PWS in VOM, suggesting an adaptation of PWS to compensate for the increase in energy demand. Maintaining a high level of PA may potentially delay the age-related decline in PWS despite an age-related increase in net CoW.

Cardiorespiratory fitness, cardiac morphology and function, and cardiovascular risk factors in long-term breast cancer survivors compared with non-cancer controls

BACKGROUND

Although anthracycline-related cardiotoxicity is widely studied, only a limited number of echocardiographic studies have assessed cardiac function in breast cancer survivors (BCSs) beyond ten years from anthracycline treatment, and the knowledge of long-term cardiorespiratory fitness (CRF) in this population is scarce. This study aimed to compare CRF assessed as peak oxygen uptake (V̇O2), cardiac morphology and function, and cardiovascular (CV) risk factors between long-term BCSs treated with anthracyclines and controls with no history of cancer.

METHODS

The CAUSE (Cardiovascular Survivors Exercise) trial included 140 BCSs recruited through the Cancer Registry of Norway, who were diagnosed with breast cancer stage II to III between 2008 and 2012 and had received treatment with epirubicin, and 69 similarly aged activity level-matched controls. All the participants underwent blood sampling, blood pressure measurements, echocardiography and cardiopulmonary exercise testing from October 2020 to August 2022.

RESULTS

BCSs were aged 59 ± 6 years and had received a cumulative dose of 357 (243 to 366) mg/m2 of epirubicin on average 11 ± 1 years before inclusion. There was no difference between BCSs and controls with respect to peak V̇O2 (27.6 ± 5.4 mL/kg/min vs. 27.1 ± 5.4 mL/kg/min, P = 0.25), 2D left ventricular ejection fraction (57 ± 3% vs. 57 ± 3%, P = 0.43), left ventricular global longitudinal strain (-20.5 ± 1.0% vs. -20.6 ± 1.0%, P = 0.46) or the proportion with N-terminal pro-brain natriuretic peptide ≥ 125 (22% vs. 20%, P = 0.93). The proportions with hypertension, dyslipidemia or diabetes did not differ between the groups.

CONCLUSION

We found that CRF, cardiac function, and CV risk profile in BCSs examined a decade after treatment with anthracyclines were similar to that in women with no history of cancer.

TRIAL REGISTRATION

clinicaltrials.gov (NCT04307407) https://clinicaltrials.gov/ct2/show/NCT04307407 .

Acute high-intensity interval exercise is superior to moderate-intensity continuous exercise in enhancing endothelial function and its associated biomarkers in sedentary young individuals: the possible involvement of lactate

Objectives

Our study investigated the effects of acute high-intensity interval exercise (HIIE) and moderate-intensity continuous exercise (MICE) on endothelial function and its associated biomarkers in sedentary young individuals.

Methods

Fifteen subjects (10M / 5F; 22 ± 2 years; BMI: 23.07 ± 4.12 kg/m2) participated in a crossover trial including three experimental conditions: HIIE, MICE, and a control session of rest (CON) in random order separated by a 7-day washout period. Endothelial function was assessed using flow-mediated dilation (FMD), mean shear rate (MSR), and circulating levels of blood lactate, VEGF, IGF-1, and irisin.

Results

Both HIIE and MICE significantly enhanced FMD% (both P < 0.001 and P < 0.01, respectively), lactate (both P < 0.001), VEGF (P < 0.001 and P < 0.01, respectively), IGF-1 (both P < 0.001), and irisin (P < 0.001 and P < 0.05, respectively), with a greater extent after HIIE compared to MICE in FMD% (P < 0.001), MSR (P < 0.05), lactate (P < 0.001), VEGF (P < 0.05), and IGF-1 (P < 0.05). Additionally, change (post-pre) in FMD% was positively correlated with changes in MSR, lactate, and VEGF in both HIIE and MICE conditions. Change in MSR was positively associated with changes in lactate and VEGF in both HIIE and MICE conditions. Furthermore, enhancement in lactate was correlated with enhancements in VEGF in both HIIE and MICE conditions.

Conclusions

Acute HIIE is a more effective method than MICE at improving endothelial function in sedentary young individuals and increases in lactate and its mediated VEGF release, attributed to increase in shear rate after exercise, are involved in regulatory mechanisms.

Maximal Fat Oxidation During Exercise in Healthy Individuals: Lack of Genetic Association with the FTO rs9939609 Polymorphism

Background/Objectives: Previous studies suggest that there is a genetically determined component of fat oxidation at rest and during exercise. To date, the FTO gene has been proposed as a candidate gene to affect fat oxidation during exercise because of the association of the "at-risk" A allele with different obesity-related factors such as increased body fat, higher appetite and elevated insulin and triglyceride levels. The A allele of the FTO gene may also be linked to obesity through a reduced capacity for fat oxidation during exercise, a topic that remains largely underexplored in the current literature. The aim of this study was to analyze the association between the FTO rs9939609 polymorphism with the rate of fat oxidation during exercise and metabolic syndrome criteria in healthy participants. Methods: A total of 80 healthy participants (41 men and 39 women) underwent comprehensive assessments, including measurements of anthropometric variables, blood pressure and blood measures of fasting glucose, triglycerides, low- and high-density lipoprotein cholesterol (LDL-c and HDL-c), insulin, interleukin-6 (IL-6) and C-reactive protein (CRP) concentrations. Additionally, the Homeostatic Model Assessment (HOMA-IR) was used to evaluate insulin resistance. Peak oxygen uptake (VO2peak) and maximal fat oxidation rate (MFO) were also measured during an incremental cycling test. FTO rs9939609 genotyping (TT, AT, AA) was performed using genomic DNA samples obtained from a buccal swab and measured with PCR. Results: There were 32 participants (40.0%) with the TT genotype; 31 (38.8%) with the AT genotype; and 17 (21.2%) with the AA genotype. Age, body characteristics, VO2peak, blood pressure and blood variables were similar across all three genotypes. However, serum insulin concentration and HOMA-IR were associated with the FTO rs9939609 genotype with higher values in AA with respect to AT and TT participants (p < 0.050). Still, MFO was similar in TT, AT and AA participants (0.35 ± 0.13, 0.37 ± 0.11, 0.33 ± 0.11 g/min, p = 0.702). In the dominant model, there was no statistical difference between TT and A allele carriers. However, the recessive model revealed that AA participants had higher values of body mass, body mass index, blood insulin concentration and HOMA-IR than T allele carriers (p < 0.050), with no differences in MFO. Conclusions: In our sample of healthy individuals, the FTO rs9939609 polymorphism was associated with several phenotypes associated with obesity and insulin resistance, particularly under the AA vs. T allele/recessive model. However, the FTO rs9939609 polymorphism was not associated with MFO during exercise as fat oxidation was similar across genotypes. This suggests that reduced fat oxidation during exercise is unlikely to be a cause of the obesogenic influence of the FTO AA genotype. Clinically, these findings suggest that the obesogenic effects of the FTO AA genotype are unlikely driven by impaired fat oxidation during exercise. Instead, attention should focus on mechanisms like appetite regulation and energy intake. Moreover, exercise interventions may still effectively mitigate obesity risk, as AA individuals retain normal fat oxidation capacity during exercise.

Effects of increasing fitness through exercise training on language comprehension in monolingual and bilingual older adults: a randomized controlled trial

Exercise training has been proposed to counteract age-related cognitive decline through improvements in cardiorespiratory fitness (CRF hypothesis). Research has focused on cognitive domains like attention and processing speed, and one cross-sectional study reported a positive relationship between CRF and language production in older adults. In a randomized controlled trial, we investigated whether these benefits could extend to language comprehension in healthy older adults, and whether bilinguals, for whom language processing is more costly, would exhibit greater benefits than monolinguals. Eighty older English monolinguals and 80 older Norwegian-English bilinguals were randomized into either a 6-month exercise training group or into a passive control group. We assessed CRF (VO2peak) and language comprehension (reaction times to spoken word monitoring) in first (L1, all participants) and second language (L2, bilinguals only), before and after the intervention. We found that monolinguals in the exercise group (compared to the control group) were faster in comprehension following the intervention. Moreover, this effect was mediated by exercise-induced increases in VO2peak, supporting the CRF hypothesis. This extends previous cross-sectional research and establishes a causal link between exercise training and speeded comprehension in older monolinguals. However, despite inducing increased VO2peak, exercise training did not affect bilingual (L1 or L2) comprehension, and bilinguals in both groups were slower after the intervention period. Exploratory analyses suggested that this slowing may be driven by participants with low L2 proficiency, but further research is needed to examine whether bilingual language processing is in fact unaffected by exercise training and its consequent improvements in CRF.

The OMNIVEG STUDY: Health outcomes of shifting from a traditional to a vegan Mediterranean diet in healthy men. A controlled crossover trial

BACKGROUND AND AIM

The Mediterranean diet is a plant-based dietary pattern with well-established health benefits such as the reduced risk of cardiovascular disease. Additionally, incorporating more plant-based foods into a Mediterranean diet may provide further health benefits. The study aimed to assess the effect of shifting from a traditional Mediterranean diet to a vegan Mediterranean diet on cardiorespiratory fitness and lipid profile in physically active and healthy men.

METHODS AND RESULTS

Participants underwent a baseline period with adhesion to the general patterns of the Mediterranean diet for three weeks and then they changed to an isocaloric vegan version of the Mediterranean diet for four weeks, with a 7-day washout period between diets. The shift from the traditional Mediterranean diet to the vegan Mediterranean diet required substituting animal-based foods with plant-based foods that contain comparable amounts of protein and fat. Fourteen participants with a mean age of 24.6 ± 7.0 years (range: 18-37 years), completed the study protocol. The change from the traditional to the vegan Mediterranean diet reduced blood concentration of total cholesterol (-22.6 mg/dl, p < 0.01, Effect size [ES] = 1.07) and low-density lipoprotein cholesterol (-12.8 mg/dl, p < 0.01, ES = 0.72). An inverse correlation was observed between the intake of dietary fibre and LDL-C (partial rho = -0.43, p = 0.040).

CONCLUSIONS

The adoption of a vegan Mediterranean diet with plant-based proteins and fats instead of the traditional Mediterranean diet improved several cardiometabolic health outcomes in physically active and healthy men.

CLINICAL TRIAL REGISTRY

NCT06008886.

Cardiorespiratory fitness, physical activity, and fatigue three months after first-ever ischemic stroke

BACKGROUND

Research on cardiorespiratory fitness (CRF) in relation to physical activity (PA) and fatigue after stroke is limited. Increased knowledge of interrelationships between these factors can help optimize rehabilitation strategies and improve health-outcomes.

OBJECTIVES

We aimed to: 1) evaluate CRF, PA, and fatigue, 2) characterize patients with impaired versus non-impaired CRF, and 3) examine associations of CRF with PA and fatigue, three months after first-ever ischemic stroke.

METHODS

In this cross-sectional study CRF was measured as peak oxygen uptake (VO2peak) by cardiopulmonary exercise testing. PA was measured using accelerometers. Fatigue was assessed with the 7-item Fatigue Severity Scale (FSS).

RESULTS

The sample (n=74, mean age 64±13 years, 36% women) had a mean VO2peak of 27.0±8.7 (86% of predicted). Fifty-one percent met the World Health Organization's recommendation of ≥150 min of moderate PA/week. Mean steps-per-day was 9316±4424 (113% of predicted). Thirty-five percent of the sample had moderate-to-high fatigue (FSS≥4), mean FSS score was 3.2±1.8.  Patients with impaired CRF (VO2peak<80% of predicted) had higher body-fat-percent (p<0.01), less moderate-to-vigorous PA (MVPA) (p<0.01) and a trend toward higher fatigue (p=0.053) compared to the non-impaired. Backward regression analysis showed that higher CRF was associated with more MVPA (unstandardized beta [95% CI]: 0.38 [0.15, 0.63], p=0.002) and less fatigue (unstandardized beta [95% CI]: -3.9 [-6.4, -1.6], p=0.004).

CONCLUSIONS

Stroke patients had lower CRF compared to reference values. Impaired CRF was mainly related to overweight. Higher CRF was associated with more MVPA and less fatigue. Exercise after stroke may be especially beneficial for patients with impaired CRF.

Test-retest reliability of exercise blood pressure and the workload-indexed systolic blood pressure slope in healthy males and females

The reliability of blood pressure (BP) measured during submaximal and maximal exercise, and confounding effects of biological sex, remain to be fully established but have implications for using exercise BP as a cardiovascular risk factor. We hypothesize that exercise BP test-retest reliability will not differ between sexes but will be higher during submaximal compared to maximal exercise. Eighty-four participants (22 ± 5 yr; 36 females) completed two maximal treadmill tests (modified Bruce protocol) separated by ≥2 days. Exercise BP was measured every 90 s using automated auscultation (Tango M2 monitor). Breath-by-breath oxygen uptake was analyzed. Test-retest reliability was assessed using two-way, mixed-effects, consistency, single-rater intraclass correlation coefficient (ICC) analysis on the total group and separated by sex at submaximal and maximal exercise. Systolic BP during submaximal (ICC = 0.65 [0.49-0.76], P < 0.01) and maximal (ICC = 0.66 [0.52-0.77], P < 0.01) exercise both displayed substantial reliability between visits. In contrast, the SBP/MET slope showed poor submaximal (ICC = 0.12 [-0.09-0.33], P = 0.13) but substantial maximal (ICC = 0.63 [0.48-0.75], P < 0.01) exercise reliability. Females showed substantial reliability in submaximal systolic BP (ICC = 0.73 [0.53-0.85], P < 0.01) and peak systolic BP (ICC = 0.74 [0.54-0.87], P < 0.01) and SBP/MET slope (ICC = 0.78 [0.60-0.88], P < 0.01); the submaximal SBP/MET slope had fair reliability (ICC = 0.28 [-0.06-0.56], P = 0.05). Males showed moderate reliability in submaximal systolic BP (ICC = 0.53 [0.26-0.72], P < 0.01) and peak systolic BP (ICC = 0.41 [0.15-0.62], P < 0.01) and SBP/MET slope (ICC = 0.48 [0.22-0.67], P < 0.01); the submaximal SBP/MET slope had poor reliability (ICC = 0.06 [-0.18-0.31], P = 0.32). Systolic BP showed similar reliability during submaximal and maximal exercise, with females demonstrating higher reliability in exercise systolic BP compared to males.NEW & NOTEWORTHY Limited work has assessed the reliability of exercise blood pressure (BP) in young healthy males and females. Our results demonstrate that systolic BP test-retest reliability did not differ between submaximal and maximal exercise. Sex-specific analysis found that females had higher reliability in exercise systolic BP than males. Despite the acceptable average reliability, exercise BP measured using automated auscultation possesses wide confidence intervals, which impact sample size requirements in future trials.

Acute effect of resistive aquatic high-intensity interval training on metabolic costs in adults

Background

The effects of Aquatic High-Intensity Interval Training (AHIIT) and resistive AHIIT (Resistive AHIIT) to improve metabolic responses were not yet known.

Objective

This study was to compare the metabolic responses and perceived effort in young healthy adults in a single session of AHIIT and resistive AHIIT.

Methods

20 healthy subjects (9 females, 11 males) performed a stationary running at a matched exercise intensity prior AHIIT and resistive AHIIT [10 × 1-min bouts of stationary running at 90% maximum heart rate (HR max) separated by 1-min active recovery] to examine the metabolic and cardiometabolic outcomes. Mixed effects models were applied to analyze the effects of group, time, and the interaction between group and time on both outcomes. The level of correlations between metabolic variables was checked by Pearson's linear correlation.

Results

There are significant differences on pre and post resting energy expenditure (REE) within both AHIIT and resistive AHIIT groups (p < 0.01) respectively as well as the subjective rate of perceived exertion (RPE) (p < 0.01) within RAHIIT group. A moderate correlation found on respiratory exertional ratio (RER) and RPE in resistive AHIIT (r = 0.534). No significant differences between groups in terms of HR max, mean heart rate (HR mean), peak oxygen consumption (VO2 peak) and total energy expenditure (TEE) (p = 0.50, p = 0.48, p = 0.81, p = 0.59).

Conclusion

Resistive AHIIT provides comparable benefits of metabolic outcomes with AHIIT. Comparable results allowed AHIIT and resistive AHIIT prescriptions precisely.

Impact of diverse aerobic exercise plans on glycemic control, lipid levels, and functional activity in stroke patients with type 2 diabetes mellitus

Aims

This study aimed to assess the effects of Low-to-Moderate Intensity Continuous Training (LMICT), Moderate-Intensity Interval Training (MIIT), and Reduced-Exertion High-Intensity Training (REHIT) on blood glucose regulation, functional recovery, and lipid levels in individuals who have experienced a stroke and are diagnosed with Type 2 Diabetes Mellitus (T2DM).

Methods

Forty-two T2DM stroke patients were randomly allocated to four groups: LMICT, MIIT, REHIT, and a control group (CON). Participants continuously monitored their blood glucose levels throughout the intervention using continuous glucose monitoring (CGM) devices. The study comprised two exercise intervention cycles: the first lasting from Day 3 to Day 14 and the second from Day 15 to Day 28, with the initial two days serving as contrasting periods. Primary outcomes encompassed CGM-derived blood glucose measurements, the Barthel Index (BI), Fugl-Meyer Assessment lower-extremity subscale (FMA-LE), and alterations in triglycerides (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-c), and low-density lipoprotein cholesterol (LDL-c).

Results

Compared with the CON, the MIIT group showed significant improvements in mean glucose (MG), glucose standard deviation (SD), time above range (TAR), and time in range (TIR). The REHIT group exhibited significantly reduced time below range (TBR), glucose SD, and coefficient of variation (CV). Regarding lipid levels, although the REHIT group achieved a significant reduction in TG levels compared with the CON, the overall effects of LMICT, MIIT, and REHIT on lipid profiles were relatively modest. Concerning functional recovery, the REHIT group significantly improved the BI and FMA-LE.

Conclusion

Although the short-term quantitative impact of exercise on lipid levels may be limited, both REHIT and MIIT significantly improved glycemic management and reduced glucose variability in post-stroke patients with Type 2 Diabetes Mellitus. Additionally, REHIT notably enhanced functional recovery.

Breathing variability during running in athletes: The role of sex, exercise intensity and breathing reserve

Highly trained aerobic athletes progressively use most of their breathing reserve with increased exercise intensity during whole-body exercise. Additionally, females typically present proportionally smaller lungs than males. Therefore, sex, exercise intensity, and breathing reserve use likely influence the volume and time in which respiratory parameters vary between consecutive breaths during whole-body exercise. However, breath-by-breath variability has been scarcely investigated during exercise. Accordingly, we sought to investigate breath-by-breath pulmonary ventilation (V̇E), tidal volume (VT), and respiratory frequency (fR) variability during a maximal treadmill incremental exercise test in 17 females and 18 males highly trained professional endurance runners. The breath-by-breath variability was analyzed by root mean square of successive differences (RMSSD) within 1-minute windows. Females had lower absolute and percent predicted forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) than males, as well as lower height-adjusted absolute FVC than males. V̇E and VT reserve use were similar between the sexes at peak exercise. While RMSSDV̇E and RMSSDfR did not change over exercise (P > 0.05), RMSSDVT progressively decreased (P < 0.001). RMSSDVT was negatively correlated with VT reserve use only in males. Females showed lower RMSSDV̇E than males during the entire exercise test (P < 0.001). At iso-V̇E reserve use, between-sex differences in RMSSDV̇E persisted (P = 0.003). Our findings indicate that exercise intensity decreases VT variability in professional runners, which is linked to VT reserve use in males but not females. Additionally, the female sex lowers V̇E variability regardless of exercise intensity and V̇E reserve use.

Post-exercise hot or cold water immersion does not alter perception of effort or neuroendocrine responses during subsequent moderate-intensity exercise

Post-exercise hot (HWI) and cold (CWI) water immersion are popular strategies used by athletes in a range of sporting contexts, such as enhancing recovery or adaptation. However, prolonged heating bouts increase neuroendocrine responses that are associated with perceptions of fatigue. Fourteen endurance-trained runners performed three trials consisting of two 45-min runs at 95% lactate threshold on a treadmill separated by 6 h of recovery. Following the first run, participants completed one of HWI (30 min, 40°C), CWI (15 min, 14°C) or control (CON, 30 min rest in ambient conditions) in a randomised order. Perceived effort and recovery were measured using ratings of perceived exertion (RPE) and the Acute Recovery and Stress Scale (ARSS), whilst physiological responses including venous concentrations of a range of neuroendocrine markers, superficial femoral blood flow, heart rate and rectal temperature were measured. Exercise increased neuroendocrine responses of interleukin-6, adrenaline and noradrenaline (all P < 0.001). Additionally, perceptions of overall recovery (P < 0.001), mental performance capacity (P = 0.02), physical performance capability (P = 0.01) and emotional balance (P = 0.03) were reduced prior to the second run. However, there was no effect of condition on these variables (P > 0.05), nor RPE (P = 0.68), despite differences in rectal temperature, superficial femoral blood flow following the first run, and participants' expected recovery prior to the intervention (all P < 0.001). Therefore, athletes may engage in post-exercise hot or cold-water immersion without negatively impacting moderate-intensity training sessions performed later the same day.

Assessing the Accuracy of Smartwatch-Based Estimation of Maximum Oxygen Uptake Using the Apple Watch Series 7: Validation Study

BACKGROUND

Determining maximum oxygen uptake (VO2max) is essential for evaluating cardiorespiratory fitness. While laboratory-based testing is considered the gold standard, sports watches or fitness trackers offer a convenient alternative. However, despite the high number of wrist-worn devices, there is a lack of scientific validation for VO2max estimation outside the laboratory setting.

OBJECTIVE

This study aims to compare the Apple Watch Series 7's performance against the gold standard in VO2max estimation and Apple's validation findings.

METHODS

A total of 19 participants (7 female and 12 male), aged 18 to 63 (mean 28.42, SD 11.43) years were included in the validation study. VO2max for all participants was determined in a controlled laboratory environment using a metabolic gas analyzer. Thereby, they completed a graded exercise test on a cycle ergometer until reaching subjective exhaustion. This value was then compared with the estimated VO2max value from the Apple Watch, which was calculated after wearing the watch for at least 2 consecutive days and measured directly after an outdoor running test.

RESULTS

The measured VO2max (mean 45.88, SD 9.42 mL/kg/minute) in the laboratory setting was significantly higher than the predicted VO2max (mean 41.37, SD 6.5 mL/kg/minute) from the Apple Watch (t18=2.51; P=.01) with a medium effect size (Hedges g=0.53). The Bland-Altman analysis revealed a good overall agreement between both measurements. However, the intraclass correlation coefficient ICC(2,1)=0.47 (95% CI 0.06-0.75) indicated poor reliability. The mean absolute percentage error between the predicted and the actual VO2max was 15.79%, while the root mean square error was 8.85 mL/kg/minute. The analysis further revealed higher accuracy when focusing on participants with good fitness levels (mean absolute percentage error=14.59%; root-mean-square error=7.22 ml/kg/minute; ICC(2,1)=0.60 95% CI 0.09-0.87).

CONCLUSIONS

Similar to other smartwatches, the Apple Watch also overestimates or underestimates the VO2max in individuals with poor or excellent fitness levels, respectively. Assessing the accuracy and reliability of the Apple Watch's VO2max estimation is crucial for determining its suitability as an alternative to laboratory testing. The findings of this study will apprise researchers, physical training professionals, and end users of wearable technology, thereby enhancing the knowledge base and practical application of such devices in assessing cardiorespiratory fitness parameters.

Cardiopulmonary and metabolic responses during a 2-day CPET in myalgic encephalomyelitis/chronic fatigue syndrome: translating reduced oxygen consumption to impairment status to treatment considerations

BACKGROUND

Post-exertional malaise (PEM), the hallmark symptom of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), represents a constellation of abnormal responses to physical, cognitive, and/or emotional exertion including profound fatigue, cognitive dysfunction, and exertion intolerance, among numerous other maladies. Two sequential cardiopulmonary exercise tests (2-d CPET) provide objective evidence of abnormal responses to exertion in ME/CFS but validated only in studies with small sample sizes. Further, translation of results to impairment status and approaches to symptom reduction are lacking.

METHODS

Participants with ME/CFS (Canadian Criteria; n = 84) and sedentary controls (CTL; n = 71) completed two CPETs on a cycle ergometer separated by 24 h. Two-way repeated measures ANOVA compared CPET measures at rest, ventilatory/anaerobic threshold (VAT), and peak effort between phenotypes and CPETs. Intraclass correlations described stability of CPET measures across tests, and relevant objective CPET data indicated impairment status. A subset of case-control pairs (n = 55) matched for aerobic capacity, age, and sex, were also analyzed.

RESULTS

Unlike CTL, ME/CFS failed to reproduce CPET-1 measures during CPET-2 with significant declines at peak exertion in work, exercise time, V ˙ e, V ˙ O2, V ˙ CO2, V ˙ T, HR, O2pulse, DBP, and RPP. Likewise, CPET-2 declines were observed at VAT for V ˙ e/ V ˙ CO2, PetCO2, O2pulse, work, V ˙ O2 and SBP. Perception of effort (RPE) exceeded maximum effort criteria for ME/CFS and CTL on both CPETs. Results were similar in matched pairs. Intraclass correlations revealed greater stability in CPET variables across test days in CTL compared to ME/CFS owing to CPET-2 declines in ME/CFS. Lastly, CPET-2 data signaled more severe impairment status for ME/CFS compared to CPET-1.

CONCLUSIONS

Presently, this is the largest 2-d CPET study of ME/CFS to substantiate impaired recovery in ME/CFS following an exertional stressor. Abnormal post-exertional CPET responses persisted compared to CTL matched for aerobic capacity, indicating that fitness level does not predispose to exertion intolerance in ME/CFS. Moreover, contributions to exertion intolerance in ME/CFS by disrupted cardiac, pulmonary, and metabolic factors implicates autonomic nervous system dysregulation of blood flow and oxygen delivery for energy metabolism. The observable declines in post-exertional energy metabolism translate notably to a worsening of impairment status. Treatment considerations to address tangible reductions in physiological function are proffered.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov, retrospectively registered, ID# NCT04026425, date of registration: 2019-07-17.

HIIT at Home: Enhancing Cardiorespiratory Fitness in Older Adults-A Randomized Controlled Trial

BACKGROUND

This study aimed to investigate the effectiveness of a 6-month home-based high-intensity interval training (HIIT) intervention to improve peak oxygen consumption (V̇O2peak) and lactate threshold (LT) in older adults.

METHODS

Two hundred thirty-three healthy older adults (60-84 years; 54% females) were randomly assigned to either 6-month, thrice-weekly home-based HIIT (once-weekly circuit training and twice-weekly interval training) or a passive control group. Exercise sessions were monitored using a Polar watch and a logbook for objective and subjective data, respectively, and guided by a personal coach. The outcomes were assessed using a modified Balke protocol combining V̇O2peak and LT measures. General linear regression models assessed between-group differences in change and within-group changes for each outcome.

RESULTS

There was a significant between-group difference in the pre-to-post change in V̇O2peak (difference: 1.8 [1.2; 2.3] mL/kg/min; exercise: +1.4 [1.0; 1.7] mL/kg/min [~5%]; control: -0.4 [-0.8; -0.0] mL/kg/min [approximately -1.5%]; effect size [ES]: 0.35). Compared with controls, the exercise group had lower blood lactate concentration (-0.7 [-0.9; -0.4] mmol/L, ES: 0.61), % of peak heart rate (-4.4 [-5.7; -3.0], ES: 0.64), and % of V̇O2peak (-4.5 [-6.1; -2.9], ES: 0.60) at the intensity corresponding to preintervention LT and achieved a higher treadmill stage (% incline) at LT (0.6 [0.3; 0.8]; ES: 0.47), following the intervention.

CONCLUSION

This study highlights the effectiveness of a home-based HIIT intervention as an accessible and equipment-minimal strategy to induce clinically meaningful improvements in cardiorespiratory fitness in older adults. Over 6 months, the exercise group showed larger improvements in all outcomes compared with the control group. Notably, the LT outcome exhibited a more pronounced magnitude of change than V̇O2peak.

Exploring the correlation of skin temperature and body composition in athletes undergoing exhaustive physical exercise

During strenuous exercise, skin temperature (Tsk) plays an essential role in thermoregulatory processes. As indicated in the literature, its response might be influenced by body composition, among other factors. Hence, the objectives of this investigation were to determine whether there is a correlation between selected body components, specifically fat tissue and muscle tissue, and Tsk during graded exercise and recovery in athletes, and to identify which body component exhibits the strongest correlation with Tsk. Participants were grouped according to their aerobic capacity (VO2max/kg). A significant main effect was observed for the test stages (p < .001, η2 = 0.71), with Tsk decreasing from the start of the exercise, significantly decreasing at 12 km/h-1 (p < .001), and then increasing after exercise, especially within the first 5 min of recovery. Weak and non-significant effect for group/stage interaction was detected (p = .374, η2 = 0.03). A significant negative correlation was found between Tsk and both total tissue fat [%] (-0.51 < r < -0.63, p < .001) and lower limb tissue fat [%] (-0.50 < r < -0.71, p < .001) across all test stages. The correlation between Tsk and BMI was inconsistent, appearing only during the first stage of exercise and throughout recovery. No correlation was observed between Tsk and skeletal muscle mass, appendicular lean soft tissue, or relative skeletal muscle index. Endurance running to exhaustion leads to a progressive decrease in the Tsk of the lower extremity, followed by rewarming during recovery. The observed inverse correlation between adipose tissue and Tsk, along with the distinct temperature trends in groups with varying levels of fat tissue, could imply that the skin and subcutaneous tissue complex may play a more intricate role in thermal energy exchange beyond its insulating function. This implies a multifaceted involvement of these tissues in thermoregulation.

Estimating cardiorespiratory fitness in older adults using the international physical activity questionnaire

Introduction

Non-exercise estimates of cardiorespiratory fitness hold great utility for epidemiological research and clinical practice. Older adults may yield the greatest benefit from fitness estimates due to limited capacity to undergo strenuous maximal exercise testing, however, few of the previously developed non-exercise equations are suitable for use in older adults. Thus, the current study developed a non-exercise equation for estimating cardiorespiratory fitness in older adults derived from the widely used International Physical Activity Questionnaire (IPAQ).

Methods

This study was a secondary analysis of baseline data from a randomized controlled trial. Participants were community-dwelling, cognitively unimpaired older adults aged 60-80 years (n = 92). They completed the IPAQ and underwent maximal exercise testing on a cycle ergometer. Stepwise linear regression was used to determine the equation in a randomly selected, sex-balanced, derivation subset of participants (n = 60), and subsequently validated using a second subset of participants (n = 32).

Results

The final equation included age, sex, body mass index and leisure time activity from the IPAQ and explained 61% and 55% of the variance in the derivation and validation groups, respectively (standard error of estimates = 3.9, 4.0). Seventy-seven and 81% of the sample fell within ±1SD (5.96 and 6.28 ml·kg-1·min-1) of measured VO2peak for the derivation and validation subgroups. The current equation showed better performance compared to equations from Wier et al. (2006), Jackson et al. (1990), and Schembre & Riebe (2011), although it is acknowledged previous equations were developed for different populations.

Conclusions

Using non-exercise, easily accessible measures can yield acceptable estimates of cardiorespiratory fitness in older adults, which should be further validated in other samples and examined in relation to public health outcomes.

Exercise-induced cortical disinhibition mediates the relationship between fitness and memory in older adults

Regular exercise benefits learning and memory in older adults, but the neural mechanisms mediating these effects remain unclear. Evidence in young adults indicates that acute exercise creates a favourable environment for synaptic plasticity by enhancing cortical disinhibition. As such, we investigated whether plasticity-related disinhibition mediated the relationship between cardiorespiratory fitness and memory function in healthy older adults (n = 16, mean age = 66.06). Participants completed a graded maximal exercise test and assessments of visual and verbal memory, followed by two counterbalanced sessions involving 20 min of either high-intensity interval training exercise or rest. Disinhibition was measured following intermittent theta burst stimulation via paired-pulse transcranial magnetic stimulation. In line with our hypotheses, we observed a positive correlation between cardiorespiratory fitness and verbal memory, which was mediated by plasticity-related cortical disinhibition. Our novel finding implicates cortical disinhibition as a mechanism through which the effects of acute bouts of exercise may translate to improved memory in older adults. This finding extends current understanding of the physiological mechanisms underlying the positive influence of cardiorespiratory fitness for memory function in older adults, and further highlights the importance of promoting exercise engagement to maintain cognitive health in later life. KEY POINTS: There are well established benefits of regular exercise for memory function in older adults, but the mechanisms are unclear. Cortical disinhibition is important for laying down new memories, and is enhanced following acute exercise in young adults, suggesting it is a potential mechanism underlying these benefits in ageing. Older adults completed a fitness test and assessments of memory, followed by two sessions involving either 20 min of exercise or rest. Disinhibition was measured following intermittent theta burst stimulation via paired-pulse transcranial magnetic stimulation. Cardiorespiratory fitness was positively associated with memory performance. Higher fitness was associated with enhanced cortical disinhibition following acute exercise. Cortical disinhibition completely mediated the relationship between fitness and memory. This novel finding provides a mechanistic account for the positive influence of cardiorespiratory fitness on memory in later life, and emphasises the importance of regular exercise for cognitive health in older populations.

Confirming the attainment of maximal oxygen uptake within special and clinical groups: A systematic review and meta-analysis of cardiopulmonary exercise test and verification phase protocols

BACKGROUND AND AIM

A plateau in oxygen uptake ([Formula: see text]) during an incremental cardiopulmonary exercise test (CPET) to volitional exhaustion appears less likely to occur in special and clinical populations. Secondary maximal oxygen uptake ([Formula: see text]) criteria have been shown to commonly underestimate the actual [Formula: see text]. The verification phase protocol might determine the occurrence of 'true' [Formula: see text] in these populations. The primary aim of the current study was to systematically review and provide a meta-analysis on the suitability of the verification phase for confirming 'true' [Formula: see text] in special and clinical groups. Secondary aims were to explore the applicability of the verification phase according to specific participant characteristics and investigate which test protocols and procedures minimise the differences between the highest [Formula: see text] values attained in the CPET and verification phase.

METHODS

Electronic databases (PubMed, Web of Science, SPORTDiscus, Scopus, and EMBASE) were searched using specific search strategies and relevant data were extracted from primary studies. Studies meeting inclusion criteria were systematically reviewed. Meta-analysis techniques were applied to quantify weighted mean differences (standard deviations) in peak [Formula: see text] from a CPET and a verification phase within study groups using random-effects models. Subgroup analyses investigated the differences in [Formula: see text] according to individual characteristics and test protocols. The methodological quality of the included primary studies was assessed using a modified Downs and Black checklist to obtain a level of evidence. Participant-level [Formula: see text] data were analysed according to the threshold criteria reported by the studies or the inherent measurement error of the metabolic analysers and displayed as Bland-Altman plots.

RESULTS

Forty-three studies were included in the systematic review, whilst 30 presented quantitative information for meta-analysis. Within the 30 studies, the highest mean [Formula: see text] values attained in the CPET and verification phase protocols were similar (mean difference = -0.00 [95% confidence intervals, CI = -0.03 to 0.03] L·min-1, p = 0.87; level of evidence, LoE: strong). The specific clinical groups with sufficient primary studies to be meta-analysed showed a similar [Formula: see text] between the CPET and verification phase (p > 0.05, LoE: limited to strong). Across all 30 studies, [Formula: see text] was not affected by differences in test protocols (p > 0.05; LoE: moderate to strong). Only 23 (53.5%) of the 43 reviewed studies reported how many participants achieved a lower, equal, or higher [Formula: see text] value in the verification phase versus the CPET or reported or supplied participant-level [Formula: see text] data for this information to be obtained. The percentage of participants that achieved a lower, equal, or higher [Formula: see text] value in the verification phase was highly variable across studies (e.g. the percentage that achieved a higher [Formula: see text] in the verification phase ranged from 0% to 88.9%).

CONCLUSION

Group-level verification phase data appear useful for confirming a specific CPET protocol likely elicited [Formula: see text], or a reproducible [Formula: see text], for a given special or clinical group. Participant-level data might be useful for confirming whether specific participants have likely elicited [Formula: see text], or a reproducible [Formula: see text], however, more research reporting participant-level data is required before evidence-based guidelines can be given.

TRIAL REGISTRATION

PROSPERO (CRD42021247658) https://www.crd.york.ac.uk/prospero.

Cardiopulmonary testing in long COVID-19 versus non-COVID-19 patients with undifferentiated Dyspnea on exertion

BACKGROUND

Dyspnea and fatigue are characteristics of long SARS-CoV-2 (COVID)-19. Cardiopulmonary exercise testing (CPET) can be used to better evaluate such patients.

RESEARCH QUESTION

How significantly and by what mechanisms is exercise capacity impaired in patients with long COVID who are coming to a specialized clinic for evaluation?

STUDY DESIGN AND METHODS

We performed a cohort study using the Mayo Clinic exercise testing database. Subjects included consecutive long COVID patients without prior history of heart or lung disease sent from the Post-COVID Care Clinic for CPET. They were compared to a historical group of non-COVID patients with undifferentiated dyspnea also without known cardiac or pulmonary disease. Statistical comparisons were performed by t-test or Pearson's chi2 test controlling for age, sex, and beta blocker use where appropriate.

RESULTS

We found 77 patients with long COVID and 766 control patients. Long COVID patients were younger (47 ± 15 vs 50 ± 10 years, P < .01) and more likely female (70% vs 58%, P < .01). The most prominent difference on CPETs was lower percent predicted peak V̇O2 (73 ± 18 vs 85 ± 23%, p < .0001). Autonomic abnormalities (resting tachycardia, CNS changes, low systolic blood pressure) were seen during CPET more commonly in long COVID patients (34 vs 23%, P < .04), while mild pulmonary abnormalities (mild desaturation, limited breathing reserve, elevated V̇E/V̇CO2) during CPET were similar (19% in both groups) with only 1 long COVID patient showing severe impairment.

INTERPRETATION

We identified severe exercise limitation among long COVID patients. Young women may be at higher risk for these complications. Though mild pulmonary and autonomic impairment were common in long COVID patients, marked limitations were uncommon. We hope our observations help to untangle the physiologic abnormalities responsible for the symptomatology of long COVID.

Maximal Aerobic Capacity as a Predictor of Performance on ACFT Total Score of ROTC Cadets

The Army Combat Fitness Test (ACFT) is a newly developed test that assesses the combat readiness of U.S. Army soldiers. The purpose of this cross-sectional study is to determine if VO2max can predict performance outcomes of the ACFT in ROTC cadets. This understanding can provide a better understanding of the aerobic demands of the ACFT. Cadets (50 males, 14 females; aged 21.43 ± 4.10 years) completed the 6-event ACFT (maximum trap-bar deadlift [MDL], standing power throw [SPT], hand-release pushups [HRPU], sprint-drag-carry shuttle run [SDC], plank [PLK], and 2-mile run [2MR]). The cadets conducted a maximal treadmill running test following the Bruce protocol. The ability of VO2max (mL·kg-1·min-1) to predict ACFT performance was determined with a linear regression model. Significance was set at p < 0.05. VO2max was significantly and positively correlated to MDL (r = .253, p = .044), HRPU (r = .486, p < .001), SDC (r = .495, p < .001), PLK (r = .628, p < .001) 2MR (r = .612, p < .001) and overall ACFT score (r = .619, p < .001) but not SPT (r = .203, p = .108). VO2max significantly explained 38% (p < .001) of the variance on the total ACFT scores with a beta coefficient of 4.338. There is a gap in understanding how VO2max impacts performance in the newly implemented ACFT. For every 1 mL·kg-1·min-1 increase in VO2max, ACFT total scores increased by 4 points. These findings support the need for further research due to the trends of U.S. Army personnel failing the 2MR, which can be associated with an insufficient aerobic capacity.

High-intensity acute exercise impacts motor learning in healthy older adults

Healthy aging is associated with changes in motor sequence learning, with some studies indicating decline in motor skill learning in older age. Acute cardiorespiratory exercise has emerged as a potential intervention to improve motor learning, however research in healthy older adults is limited. The current study investigated the impact of high-intensity interval exercise (HIIT) on a subsequent sequential motor learning task. Twenty-four older adults (aged 55-75 years) completed either 20-minutes of cycling, or an equivalent period of active rest before practicing a sequential force grip task. Skill learning was assessed during acquisition and at a 6-hour retention test. In contrast to expectation, exercise was associated with reduced accuracy during skill acquisition compared to rest, particularly for the oldest participants. However, improvements in motor skill were retained in the exercise condition, while a reduction in skill was observed following rest. Our findings indicate that high-intensity exercise conducted immediately prior to learning a novel motor skill may have a negative impact on motor performance during learning in older adults. We also demonstrated that exercise may facilitate early offline consolidation of a motor skill within this population, which has implications for motor rehabilitation.

Indirect Calorimetry-Based Novel Approach for Evaluating Metabolic Flexibility and Its Association with Circulating Metabolic Markers in Middle-Aged Subjects

We propose a novel method for assessing metabolic flexibility (MF) through indirect calorimetry. A total of twenty healthy volunteers (10 females; 10 males) aged 45-65 were categorized into a Low-Intensity activity group (LI, 0-1 session of 1 h per week) and a High-Intensity activity group (HI, 5-6 sessions of 2 h per week). Volunteers underwent a stepwise exercise test on a cycle ergometer, connected to a calorimeter, to examine respiratory gas exchange to evaluate peak fatty acid Oxidation (PFO) and peak carbohydrate oxidation (PCO). Circulating peroxisome proliferator-activated receptor α (PPARα) biomarkers, docosahexaenoic acid/eicosapentaenoic acid (DHA/EPA) ratio and N-oleoylethanolamine (OEA), and the endocannabinoid- 2-arachidonoylglycerol (2-AG), were evaluated. We developed two MF parameters: the MF index (MFI), calculated by the product of PFO normalized per kg of fat-free mass (FFM) and the percentage of VO2max at PFO, and the peak energy substrates' oxidation (PESO), computed by summing the kilocalories from the PFO and PCO, normalized per kg FFM. The MFI and PESO were significantly different between the HI and LI groups, showing strong correlations with the circulating bioactive substances. Higher DHA/EPA ratio (p ≤ 0.05) and OEA (p ≤ 0.01), but lower 2-AG levels (p ≤ 0.01) were found in the HI group. These new parameters successfully established a functional link between MF and the balance of PPARα/endocannabinoid systems.

Step by Step: Evaluation of Cardiorespiratory Fitness in Healthy Children, Young Adults, and Patients with Congenital Heart Disease Using a Simple Standardized Stair Climbing Test

(1) Background: Cardiorespiratory fitness (CRF) is known to be a prognostic factor regarding long-term morbidity and mortality. This study aimed to develop a standardized Stair Climbing Test (SCT) with a reliable correlation to spiroergometry and the 6MWT which can be used in healthy children as well as patients with congenital heart disease (CHD) and a restricted exercise capacity. (2) Methods: A total of 28 healthy participants aged 10-18 years were included. We tested the individuals' CRF by cardiopulmonary exercise testing (CPET) on a treadmill, the 6MWT, and a newly developed Stair Climbing Test (SCT). For the SCT, we defined a standardized SCT protocol with a total height of 13.14 m to achieve maximal exercise effects while recording time and vital parameters. To compare the SCT, the 6 Min Walking Test, and CPET, we introduced an SCT-Index that included patient data (weight, height) and time. To assess the SCT's feasibility for clinical practice, we also tested our protocol with five adolescents with complex congenital heart disease (i.e., Fontan circulation). (3) Results: A strong correlation was observed between SCT-Index and O2 pulse (r = 0.921; p < 0.001). In addition, when comparing the time achieved during SCT (tSCT) with VO2max (mL/min/kg) and VO2max (mL/min), strong correlations were found (r = -0.672; p < 0.001 and r = -0.764; p < 0.001). Finally, we determined a very strong correlation between SCT-Index and VO2max (mL/min) (r = 0.927; p = <0.001). When comparing the 6MWD to tSCT, there was a moderate correlation (r = -0.544; p = 0.003). It appears to be feasible in patients with Fontan circulation. (4) Conclusions: We were able to demonstrate that there is a significant correlation between our standardized SCT and treadmill CPET. Therefore, we can say that the SCT can be used as an easy supplement to CPET and in certain contexts, it can also be used as a screening tool when CPET is not available. The advantages would be that the SCT is a simple, quick, cost-effective, and reliable standardized (sub)maximal exercise test to evaluate CRF in healthy children on a routine basis. We can even assume that it can be used in patients with congenital heart disease.

Measurements of in vivo skeletal muscle oxidative capacity are lower following sustained isometric compared with dynamic contractions

Human skeletal muscle oxidative capacity can be quantified non-invasively using 31-phosphorus magnetic resonance spectroscopy (31P-MRS) to measure the rate constant of phosphocreatine (PCr) recovery (kPCr) following contractions. In the quadricep muscles, several studies have quantified kPCr following 24-30 s of sustained maximal voluntary isometric contraction (MVIC). This approach has the advantage of simplicity but is potentially problematic because sustained MVICs inhibit perfusion, which may limit muscle oxygen availability or increase the intracellular metabolic perturbation, and thus affect kPCr. Alternatively, dynamic contractions allow reperfusion between contractions, which may avoid limitations in oxygen delivery. To determine whether dynamic contraction protocols elicit greater kPCr than sustained MVIC protocols, we used a cross-sectional design to compare quadriceps kPCr in 22 young and 11 older healthy adults following 24 s of maximal voluntary: (1) sustained MVIC and (2) dynamic (MVDC; 120°·s-1, 1 every 2 s) contractions. Muscle kPCr was ∼20% lower following the MVIC protocol compared with the MVDC protocol (p ≤ 0.001), though this was less evident in older adults (p = 0.073). Changes in skeletal muscle pH (p ≤ 0.001) and PME accumulation (p ≤ 0.001) were greater following the sustained MVIC protocol, and pH (p ≤ 0.001) and PME (p ≤ 0.001) recovery were slower. These results demonstrate that (i) a brief, sustained MVIC yields a lower value for skeletal muscle oxidative capacity than an MVDC protocol of similar duration and (ii) this difference may not be consistent across populations (e.g., young vs. old). Thus, the potential effect of contraction protocol on comparisons of kPCr in different study groups requires careful consideration in the future.

Exploring the role of sex in the association of late chronotype on cardiorespiratory fitness

Circadian rhythms differ between young adult males and females. For example, males tend to be later chronotypes, preferring later timing of sleep and activity, than females. Likewise, there are sex differences in body composition and cardiorespiratory fitness. Few studies have investigated the association between circadian rhythms, cardiorespiratory fitness, and body composition. We sought to determine whether chronotype and circadian phase were associated with cardiorespiratory fitness, body composition, and anthropometric measures in sedentary males and females. Fifty-nine adults participated in the study. Circadian phase and chronotype were measured using dim light melatonin onset (DLMO) and the Morningness-Eveningness Questionnaire (MEQ) score. We used peak oxygen uptake (VO2peak ) results from a maximal graded exercise test to assess cardiorespiratory fitness. Body composition, BMI, and circumferences were collected as markers of adiposity. We observed a sex difference in the association between DLMO and VO2peak . For males, a later DLMO was associated with a lower VO2peak . VO2peak did not vary based on DLMO in females. Later circadian phase was also associated with increased body fat percentage, fat mass index, and abdominal circumference in males, but not females. Collectively, these results suggest that males who are later chronotypes may be at risk of obesity and low cardiorespiratory fitness.

The effects of separate and simultaneous upper and lower body cycling on cardiorespiratory responses in young men

BACKGROUND

The aim of the present study was to examine the relative cardiorespiratory and perceptual responses to upper body ergometry, lower body ergometry, and combined upper and lower body ergometry at increasing exercising intensities.

METHODS

Eight healthy males between 19 and 30 years of age completed three exercise sessions over seven days that included graded leg ergometry, arm ergometry, and combined arm and leg ergometry in counterbalanced fashion. During leg-only and arm-only sessions, participants exercised at workloads of 0, 32, 64, and 95 W. The combined session involved simultaneous arm and leg ergometry at 0, 32, 64, and 95 W, thus eliciting double the total power output of arm-only and leg-only sessions.

RESULTS

At all workloads, oxygen consumption and minute ventilation responses were greater during combined arm and leg exercise than during leg-only or arm-only exercise. However, the pattern of changes in heart rate, systolic blood pressure, rate pressure product, and rating of perceived exertion (RPE) were similar in response to arm-only and combined upper and lower body exercise, despite combined exercise involving double the workload. These cardiorespiratory and perceptual responses were significantly lower during leg-only only exercise.

CONCLUSIONS

The results of the study add to limited research comparing physiological and perceptual responses to upper, lower, and combined upper and lower body exercise. The findings highlight heightened cardiorespiratory and perceptual responses to upper body exercise alone or in combination with lower body exercise. Training that combines upper and lower body may create higher power output and elicit greater caloric expenditure while eliciting similar cardiovascular responses as upper body only exercise at moderate and higher intensities.

Response of skin temperature, blood ammonia and lactate during incremental exercise until exhaustion in elite athletes

The study aimed to evaluate the lower limb skin temperature (Tsk) and blood concentrations of lactate (LA) and ammonia (NH3) during exercise and recovery. Eleven elite sprint athletes (25 ± 3.4 yrs) and 11 elite endurance athletes (24.45 ± 5.4 yrs) performed an incremental running test until exhaustion. Body composition was estimated using the DXA method. Thermograms of the anterior and posterior surfaces of the lower limbs were recorded at rest, before each test stage (every 3 min, starting from 10 km h-1 and increasing by 2 km h-1), and in the 5th, 10th, 15th, 20th, and 30th minute of recovery. Endurance athletes had a higher maximum oxygen uptake than sprint athletes (5.0 ± 0.7 vs 4.3 ± 0.4 l·kg-1, p = 0.018), lower percentage of lean content (79 ± 2 vs 83 ± 2%, p < 0.001), and a higher percentage of fat content in the lower limbs (17 ± 2 vs 12 ± 2%, p < 0.001). In both groups, a significant decrease in Tsk was observed compared to resting value (endurance athletes-31.5 ± 0.6 °C; sprint athletes-32.3 ± 0.6 °C), during exercise (p < 0.001) and rewarming during recovery (p < 0.001). However, endurance athletes had a lower Tsk than sprint athletes at the exhaustion point (30.0 ± 1.1 vs 31.6 ± 0.8 °C, p < 0.05) and the pattern of change in Tsk differed between groups (p < 0.001). Tsk in the endurance athletes group decreased throughout the exercise protocol and returned more rapidly to initial values during recovery, while Tsk in the sprint group stabilised between moderate intensity and exhaustion, recovering more slowly after exercise. Both LA (endurance athletes-max 10.2 ± 1.5; sprint athletes-max 10.1 ± 1.4 mmol⋅L-1, p < 0.001) and NH3 (endurance athletes-max 75.6 ± 11.5; sprint athletes-max 76.7 ± 9.0 mmol⋅L-1, p < 0.001) increased during exercise and decreased during recovery (p < 0.001). During exercise, lower levels and slower increases in LA were observed during exercise in the endurance athletes' group (p < 0.05). A negative correlation was revealed between Tsk and fat percentage (r = -0.43 to -0.71, p < 0.05). Tsk was positively correlated with LA during recovery (r = 0.43 to 0.48, p < 0.05), and negatively during recovery (r = -0.45 to -0.54, p < 0.05). Differences between groups in maximum aerobic capacity, the pattern of change in Tsk, and the correlation between Tsk and LA suggest that individuals who decrease less Tsk during exercise and higher Tsk during recovery are those with better aerobic capacity. In addition, athletes with less body fat dissipate heat from their tissues more efficiently.

Analysis of Course of Changes in Blood Lactate Concentration in Response to Graded Exercise Test and Modified Wingate Test in Adolescent Road Cyclists

BACKGROUND

The purpose of this study was to analyze the course of changes in the blood lactate (BL) concentration in response to the graded exercise test (GXT) and the modified Wingate test (MWT).

METHODS

This study involved 23 male highly trained road cyclists (age: 16.2 ± 1.1 years; experience: 5.0 ± 2.1 years; VO2max 59.0 ± 3.5 mL × kg-1 × min-1). The analysis of BL concentration was conducted using an enzymatic-amperometric electrochemical technique.

RESULTS

Our study provided the following information: (i) peak BL concentration in response to GXT (12.86 ± 2.32 mmol × L-1) and MWT (12.85 ± 1.47 mmol × L-1) is expected around the third minute after the completion of the trial; (ii) 60 min is not a sufficient period for BL concentration to return to resting values after GXT; (iii) post-GXT BL removal during the 60 min period is unsteady (3-20 min: -2.6 ± -0.6% × min-1; 20-60 min: -1.6 ± -0.3% × min-1; p-value for comparison < 0.01), whereas post-MWT BL removal during the 12 min period appears to be constant (3-6 min: -2.4 ± -5.6% × min-1, 6-9 min: -2.6 ± -1.8 % × min-1; 9-12 min: -3.1 ± -2.1 % × min-1; p-value for all comparisons < 0.01).

CONCLUSIONS

When aiming to obtain valuable data regarding the course of changes in BL concentration during the post-exertion period, it is essential to consider the number of measurements and the time points in sample collection for analysis.

Sensor location influences the associations between IMU and motion capture measurements of impact landing in healthy male and female runners at multiple running speeds

This study investigated the relationships between inertial measurement unit (IMU) acceleration at multiple body locations and 3D motion capture impact landing measures in runners. Thirty healthy runners ran on an instrumented treadmill at five running speeds (9-17 km/h) during 3D motion capture. Axial and resultant acceleration were collected from IMUs at the distal and proximal tibia, distal femur and sacrum. Relationships between peak acceleration from each IMU location and patellofemoral joint (PFJ) peak force and loading rate, impact peak and instantaneous vertical loading rate (IVLR) were investigated using linear mixed models. Acceleration was positively related to IVLR at all lower limb locations (p < 0.01). Models predicted a 1.9-3.2 g peak acceleration change at the tibia and distal femur, corresponding with a 10% IVLR change. Impact peak was positively related to acceleration at the distal femur only (p < 0.01). PFJ peak force was positively related to acceleration at the distal (p = 0.03) and proximal tibia (p = 0.03). PFJ loading rate was positively related to the tibia and femur acceleration in males only (p < 0.01). These findings suggest multiple IMU lower limb locations are viable for measuring peak acceleration during running as a meaningful indicator of IVLR.

Validation of the maximal cardiopulmonary exercise test in adolescents with major depressive disorder and comparison of cardiorespiratory fitness with sex- and age-related control values

Endurance training has been shown to be effective in treating adolescents with major depressive disorder (MDD). To integrate endurance training into the therapeutic setting and the adolescents' daily lives, the current performance status of the adolescents should be accurately assessed. This study aims to examine adolescents with MDD concerning exhaustion criteria during a cardiopulmonary exercise test (CPET), as well as to compare the values obtained thereon with sex- and age-related control values. The study included a retrospective examination of exhaustion criteria ((i) oxygen consumption (V̇O2) plateau, (ii) peak respiratory exchange ratio (RERpeak) > 1.0, (iii) peak heart rate (HRpeak) ≥ 95% of the age-predicted maximal HR, and (iv) peak blood lactate concentration (BLCpeak) > 8.0 mmol⋅L-1) during a graded CPET on a cycle ergometer in adolescents with MDD (n = 57). Subsequently, maximal V̇O2, peak minute ventilation, V̇O2 at the first ventilatory threshold, and peak work rate of participants who met at least two of four criteria were compared with published control values using an independent-sample t-test. Thirty-three percent of the total population achieved a V̇O2 plateau and 75% a RERpeak > 1.0. The HR and BLC criteria were met by 19% and 22%, respectively. T-test results revealed significant differences between adolescents with MDD and control values for all outcomes. Adolescents with MDD achieved between 56% and 83% of control values.   Conclusions: The study shows that compared with control values, fewer adolescents with MDD achieve the exhaustion criteria on a CPET and adolescents with MDD have significantly lower cardiorespiratory fitness.   Clinical trial registration: No. U1111-1145-1854. What is Known: • It is already known that endurance training has a positive effect on depressive symptoms. What is New: • A relevant proportion of adolescents with major depressive disorder do not achieve their V̇O2max during a graded cardiopulmonary exercise test. • Adolescents with major depressive disorder have significantly lower cardiorespiratory fitness compared to sex- and age-related control values.

Ageing attenuates exercise-enhanced motor cortical plasticity

Cardiorespiratory exercise is known to modulate motor cortical plasticity in young adults, but the influence of ageing on this relationship is unknown. Here, we compared the effects of a single session of cardiorespiratory exercise on motor cortical plasticity in young and older adults. We acquired measures of cortical excitatory and inhibitory activity of the primary motor cortex using transcranial magnetic stimulation (TMS) from 20 young (mean ± SD = 25.30 ± 4.00 years, 14 females) and 20 older (mean ± SD = 64.10 ± 6.50 years, 11 females) healthy adults. Single- and paired-pulse TMS measurements were collected before and after a 20 min bout of high-intensity interval cycling exercise or an equivalent period of rest, and again after intermittent theta burst stimulation (iTBS). In both young (P = 0.027, Cohen's d = 0.87) and older adults (P = 0.006, Cohen's d = 0.85), there was an increase in glutamatergic excitation and a reduction in GABAergic inhibition from pre- to postexercise. However, in contrast to younger adults, older adults showed an attenuated plasticity response to iTBS following exercise (P = 0.011, Cohen's d = 0.85). These results demonstrate an age-dependent decline in cortical plasticity and indicate that a preceding bout of high-intensity interval exercise might be less effective for enhancing primary motor cortex plasticity in older adults. Our findings align with the hypothesis that the capacity for cortical plasticity is altered in older age. KEY POINTS: Exercise enhances motor cortical plasticity in young adults, but how ageing influences this effect is unknown. Here, we compared primary motor cortical plasticity responses in young and older adults before and after a bout of high-intensity interval exercise and again after a plasticity-inducing protocol, intermittent theta burst stimulation. In both young and older adults, exercise led to an increase in glutamatergic excitation and a reduction in GABAergic inhibition. Our key result was that older adults showed an attenuated plasticity response to theta burst stimulation following exercise, relative to younger adults. Our findings demonstrate an age-dependent decline in exercise-enhanced cortical plasticity and indicate that a preceding bout of high-intensity interval exercise might be less effective for enhancing primary motor cortex plasticity in older adults.

Cardiorespiratory fitness in women after severe pre-eclampsia

AIMS

To objectively study cardiorespiratory fitness (CRF) and physical activity (PA) and to evaluate limiting factors of exercise intolerance associated with poor CRF after severe pre-eclampsia.

METHODS

In this single-centre, cross-sectional study, CRF was measured as peak oxygen uptake (VO2peak) during a cardiopulmonary exercise test (CPET) on a treadmill in women 7 years after severe pre-eclampsia. Ninety-six patients and 65 controls were eligible to participate. Cardiac output (CO) was measured by impedance cardiography. PA was measured using accelerometers.

RESULTS

In 62 patients and 35 controls (mean age 40 ± 3 years), the VO2peak (in mL·kg-1·min-1) values were 31.4 ± 7.2 and 39.1 ± 5.4, respectively (p<0.01). In the patients, the COpeak was (9.6 L·min-1), 16% lower compared to controls (p<0.01). Twelve patients (19%) had a cardiac limitation to CPET. Twenty-three (37%) patients and one (3%) control were classed as unfit, with no cardiopulmonary limitations. The patients demonstrated 25% lower PA level (in counts per minute; p<0.01) and 14% more time being sedentary (p<0.01), compared with the controls. Twenty-one patients (34%) compared with four (17%) controls did not meet the World Health Organization's recommendations for PA (p=0.02). Body mass index and PA level accounted for 65% of the variability in VO2peak.

CONCLUSION

Significantly lower CRF and PA levels were found in patients on long-term follow-up after severe pre-eclampsia. CPET identified cardiovascular limitations in one third of patients. One third appeared unfit, with adiposity and lower PA levels. These findings highlight the need for clinical follow-up and exercise interventions after severe pre-eclampsia.

A Cardiopulmonary Exercise Testing for Prescribing High-Intensity Interval Training Sessions with Elastic Resistance

This study aims to analyze the agreement of cardiopulmonary variables between a cardiopulmonary exercise test with elastic resistance (CPxEL) and high-intensity interval exercise with elastic resistance (EL-HIIE).

METHODS

Twenty-two physically independent participants were recruited. Visit one consisted of conducting a health survey and anthropometric assessment. On visit two, the participants performed CPxEL. After seven days, on visit three, the participants performed EL-HIIE. The CPxEL was carried out on a rubber mat demarcated by lines representing eight stages. The test consisted of alternating back and forth steps against elastic resistance. The increments were performed at a rate of one stage per minute, following a cadence controlled by a metronome calibrated by beats per minute (bpm). The EL-HIIE was performed at the stage corresponding to an intensity of ~85% VO2max, as determined by CPxEL. The EL-HIIE consisted of 10 × 1 min (work):1 min (passive rest), with a cadence of 200 bpm. Cardiopulmonary parameters, heart rate (HR), and oxygen consumption (VO2) were measured during exercise. Bland-Altman was applied to analyze the agreement between the HR and VO2 found in EL-HIIE and the values prescribed by CPxEL (~85-90% VO2max).

RESULTS

The HRpeak and VO2peak in the EL-HIIE showed good agreement with the VO2CPxEL and HRCPxEL values, showing an average difference of (-1.7 mL·kg-1·min-1) and (0.3 bpm).

CONCLUSIONS

The results of the present study demonstrate the agreement of cardiopulmonary variables between the CPxEL and the EL-HIIE. Therefore, for a more specific prescription of EL-HIIE intensity, CPxEL can be used.

From juniors to seniors: changes in training characteristics and aerobic power in 17 world-class cross-country skiers

Purpose: To compare training characteristics and aerobic power (VO2max) between the most successful junior and senior seasons of world-class cross-country (XC) skiers and to identify differences between sexes and among sprint and distance skiers. Methods: Retrospective analysis was conducted on self-reported training and VO2max tests of ten male and seven female world-class XC-skiers, collectively holding 38 Olympic medals. Training was categorized by form (endurance, strength, speed, other) and mode (specific, unspecific) and was divided into low- (LIT), moderate- (MIT), and high-intensity training (HIT). Results: Total training increased by 203 ± 130 h (35% ± 31%, p < .001, large effect) and 78 ± 69 sessions (21% ± 24%, p < .001, very large effect). Junior training volume (658 ± 107 h) did not correlate with senior volume (861 ± 74 h) but correlated negatively with changes in volume (r = -.822, p < .001). No sex differences were observed related to total volume, but distance skiers increased their total volume more than sprint skiers (p = .037, large effect). Endurance training increased by 197 ± 117 h (p < .001; large effect) tied to increased low-intensity training (186 ± 115 h, p < .001; large effect) and moderate-intensity training (13 ± 7 h, p < .001; large effect). Training intensity distribution (% LIT/MIT/HIT) was 91/3/6 in junior and 92/4/4 in senior season. Women demonstrated greater increase of unspecific modes (100 ± 58 vs. 37 ± 44 h, p = .022; large effect) and strength training (25 ± 23 vs. -3 ± 17 h, p = .010, large effect). Men improved absolute (8% ± 5%; p = .009; large effect) and relative VO2max (6% ± 4%; p = .016; large effect) from junior to senior, while women only increased relative VO2max (7% ± 5%, p = .012; large effect). Conclusion: This study provides novel information regarding changes in training characteristics and aerobic power from junior to senior age in world-class XC-skiers. Overall, the enhanced training volume during this transition was primarily driven by increased LIT and MIT and the exceptionally high relative VO2max at junior age further increased in both sexes.

Effects of a laboratory-based aerobic exercise intervention on brain volume and cardiovascular health markers: protocol for a randomised clinical trial

INTRODUCTION

Physical activity (PA) has beneficial effects on brain health and cardiovascular disease (CVD) risk. Yet, we know little about whether PA-induced changes to physiological mediators of CVD risk influence brain health and whether benefits to brain health may also explain PA-induced improvements to CVD risk. This study combines neurobiological and peripheral physiological methods in the context of a randomised clinical trial to better understand the links between exercise, brain health and CVD risk.

METHODS AND ANALYSIS

In this 12-month trial, 130 healthy individuals between the ages of 26 and 58 will be randomly assigned to either: (1) moderate-intensity aerobic PA for 150 min/week or (2) a health information control group. Cardiovascular, neuroimaging and PA measurements will occur for both groups before and after the intervention. Primary outcomes include changes in (1) brain structural areas (ie, hippocampal volume); (2) systolic blood pressure (SBP) responses to functional MRI cognitive stressor tasks and (3) heart rate variability. The main secondary outcomes include changes in (1) brain activity, resting state connectivity, cortical thickness and cortical volume; (2) daily life SBP stress reactivity; (3) negative and positive affect; (4) baroreflex sensitivity; (5) pulse wave velocity; (6) endothelial function and (7) daily life positive and negative affect. Our results are expected to have both mechanistic and public health implications regarding brain-body interactions in the context of cardiovascular health.

ETHICS AND DISSEMINATION

Ethical approval has been obtained from the University of Pittsburgh Institutional Review Board (IRB ID: 19020218). This study will comply with the NIH Data Sharing Policy and Policy on the Dissemination of NIH-Funded Clinical Trial Information and the Clinical Trials Registration and Results Information Submission rule.

TRIAL REGISTRATION NUMBER

NCT03841669.

Physiological Demands and Characteristics of Movement During Simulated Combat

INTRODUCTION

Military tasks place considerable physiological demands on the soldier. It is therefore important to know the energy expenditure of soldiers while solving tasks in different environments. The purpose of this study was to describe the cardiorespiratory demands of certain movements and activities on ground combat soldiers during military field operations using body sensors and simulated combat.

MATERIALS AND METHODS

Movement characteristics and cardiorespiratory responses were assessed in 42 soldiers (three women) in the Swedish Army. The different posts assessed were commander, combat engineer, driver, and gunner. The military field exercises examined were urban operations and retrograde operations in rough terrain. Measurements included (1) body mass, (2) heart rate (HR) including maximal (HRmax), (3) velocity, (4) accelerations/decelerations, and (5) distance moved. Maximal aerobic capacity (V̇O2peak, mL·kg-1·min-1) was tested in a laboratory setting when wearing combat gear and body armor.

RESULTS

There was a weak positive correlation (r = 0.41 and 0.28, both P < .05) between VO2peak and percentage of time over 40% and 50% of maximal aerobic capacity during simulated combat. No differences were found for the different posts in time spent over 40% or 50% of maximal aerobic capacity and 76% of their HRmax (P > .05). Wearing combat gear and additional load while solving tasks resulted in mean HR varying between 98 and 111 beats·min-1, corresponding with 50-57% of the soldiers HRmax. Studying all exercises, mean HR was 105 ± 11 beats min-1, 54 ± 5% of HRmax corresponding to light work intensity. Soldiers performed between 2.8 and 4.9 accelerations/min in the different exercises. A significant correlation between V̇O2peak (mL kg-1 min-1) and acceleration and m/min were found, implying that soldiers with good aerobic capacity were able to cope better with tasks requiring quick movements.

CONCLUSION

Conducting military operations in urban terrain and retrograde operations in rough terrain strains ground combat soldiers' cardiorespiratory system, with work intensities close to 40% of maximal aerobic capacity in 15-33% of mission time. Tasks with external load carriage include change of direction, accelerations, bounds, and jumping over obstacles, and physical fitness tests should replicate this. Findings in this study also add objective data to the physiological demands of work performed by combat soldiers while conducting urban operations and retrograde operations in rough terrain. These findings could be used to develop a model for classifying work demands for ground combat forces.

The acute effects of exercise intensity and inorganic nitrate supplementation on vascular health in females after menopause

Menopause is associated with reduced nitric oxide bioavailability and vascular function. Although exercise is known to improve vascular function, this is blunted in estrogen-deficient females post-menopause (PM). Here, we examined the effects of acute exercise at differing intensities with and without inorganic nitrate (NO3-) supplementation on vascular function in females PM. Participants were tested in a double-blinded, block-randomized design, consuming ∼13 mmol NO3- in the form of beetroot juice (BRJ; n = 12) or placebo (PL; n = 12) for 2 days before experimental visits and 2 h before testing. Visits consisted of vascular health measures before (time point 0) and every 30 min after (time points 60, 90, 120, 150, and 180) calorically matched high-intensity exercise (HIE), moderate-intensity exercise (MIE), and a nonexercise control (CON). Blood was sampled at rest and 5-min postexercise for NO3-, NO2-, and ET-1. BRJ increased N-oxides and decreased ET-1 compared with PL, findings which were unchanged after experimental conditions (P < 0.05). BRJ improved peak Δflow-mediated dilation (FMD) compared with PL (P < 0.05), defined as the largest ΔFMD for each individual participant across all time points. FMD across time revealed an improvement (P = 0.05) in FMD between BRJ + HIE versus BRJ + CON, while BRJ + MIE had medium effects compared with BRJ + CON. In conclusion, NO3- supplementation combined with HIE improved FMD in postmenopausal females. NO3- supplementation combined with MIE may offer an alternative to those unwilling to perform HIE. Future studies should test whether long-term exercise training at high intensities with NO3- supplementation can enhance vascular health in females PM.NEW & NOTEWORTHY This study compared exercise-induced changes in flow-mediated dilation after acute moderate- and high-intensity exercise in females postmenopause supplementing either inorganic nitrate (beetroot juice) or placebo. BRJ improved peak ΔFMD postexercise, and BRJ + HIE increased FMD measured as FMD over time. Neither PL + MIE nor PL + HIE improved FMD. These findings suggest that inorganic nitrate supplementation combined with high-intensity exercise may benefit vascular health in females PM.

Criterion Validity and Responsiveness of Estimated Cardiorespiratory Fitness Models in Patients with Inflammatory Joint Disease

Cardiorespiratory fitness (CRF) is an excellent marker of overall health. This study aimed to assess criterion validity and responsiveness of estimated CRF models (eCRF) in patients with inflammatory joint disease (IJD). CRF was measured directly as peak oxygen uptake (VO2peak) by a Cardiopulmonary Exercise Test (CPET), while one generic eCRF model (eCRFGEN) and two disease-specific eCRF models (eCRFALT and eCRFPGA) were used to estimate CRF at baseline and after 3 months in 55 Norwegian patients with IJD. Moderate correlations were observed between eCRFGEN, eCRFALT, eCRFPGA, and VO2peak at baseline (ICC 0.60, 0.64 and 0.62, respectively) and 3 months (ICC 0.62, 0.65 and 0.57, respectively). All eCRF models overestimated measured VO2peak, and there was large variability in agreement of individual measurements at baseline and at 3 months. Weak correlations were observed for responsiveness of eCRFGEN (ICC 0.39), eCRFALT (ICC 0.40) and eCRFPGA (ICC 0.39). Mean differences between change in eCRF models and change in VO2peak were small, but the wide limits of agreement exceeded the pre-defined clinically acceptable margins. The eCRF models possessed adequate ability to detect ≥3.5 mL/kg/min improvement in VO2peak. eCRF may suffice for group-level assessment, but caution is advised when applying eCRF to individual patients with IJD.

Spatiotemporal and kinematic adjustments in master runners may be associated with the relative physiological effort during running

Master runners maintain a similar running economy to young runners, despite displaying biomechanical characteristics that are associated with a worse running economy. This apparent paradox may be explained by a greater physiological effort-i.e., percentage of maximal oxygen uptake (VO2-max)-that master runners perform at a given speed. Moreover, age-related responses to non-exhaustive sustained running are yet underexplored. The aims of this study were, therefore, to examine if biomechanical adjustments in master runners are physiological-effort dependent, and to explore the age-related biomechanical changes during a non-exhaustive sustained run. Young (23.9 ± 6; n = 12) and master (47.3 ± 6.9; n = 12) runners performed a sustained 30-minute treadmill run matched for relative physiological effort (70% VO2-max), while spatiotemporal and lower-limb kinematic characteristics were collected during the 1st and 30th minute. Group differences were observed in step/stride length, knee touch-down angle, and knee stiffness. However, both groups of runners had a similar step frequency, vertical center of mass oscillation, and knee range of motion. Age-related adjustment in these latter characteristics may thus not be an inevitable result of the aging process but rather a strategy to maintain running economy. The relative physiological effort of runners should, therefore, be considered when examining age-related adjustments in running biomechanics.

Cardiorespiratory Fitness in Individuals Post-stroke: Reference Values and Determinants

OBJECTIVE

To provide reference values of cardiorespiratory fitness for individuals post-stroke in clinical rehabilitation and to gain insight in characteristics related to cardiorespiratory fitness post stroke.

DESIGN

A retrospective cohort study. Reference equations of cardiopulmonary fitness corrected for age and sex for the fifth, 25th, 50th, 75th, and 95th percentile were constructed with quantile regression analysis. The relation between patient characteristics and cardiorespiratory fitness was determined by linear regression analyses adjusted for sex and age. Multivariate regression models of cardiorespiratory fitness were constructed.

SETTING

Clinical rehabilitation center.

PARTICIPANTS

Individuals post-stroke who performed a cardiopulmonary exercise test as part of clinical rehabilitation between July 2015 and May 2021 (N=405).

MAIN OUTCOME MEASURES

Cardiorespiratory fitness in terms of peak oxygen uptake (V˙O2peak) and oxygen uptake at ventilatory threshold (V˙O2-VT).

RESULTS

References equations for cardiorespiratory fitness stratified by sex and age were provided based on 405 individuals post-stroke. Median V˙O2peak was 17.8[range 8.4-39.6] mL/kg/min and median V˙O2-VT was 9.7[range 5.9-26.6] mL/kg/min. Cardiorespiratory fitness was lower in individuals who were older, women, using beta-blocker medication, and in individuals with a higher body mass index and lower motor ability.

CONCLUSIONS

Population specific reference values of cardiorespiratory fitness for individuals post-stroke corrected for age and sex were presented. These can give individuals post-stroke and health care providers insight in their cardiorespiratory fitness compared with their peers. Furthermore, they can be used to determine the potential necessity for cardiorespiratory fitness training as part of the rehabilitation program for an individual post-stroke to enhance their fitness, functioning and health. Especially, individuals post-stroke with more mobility limitations and beta-blocker use are at a higher risk of low cardiorespiratory fitness.

A 3-minute recumbent stepper test in chronic stroke

BACKGROUND

Persons with stroke often have difficulty achieving target heart rate (HR) during graded exercise testing (GXT), which is known to limit test sensitivity for detecting clinically relevant cardiac conditions. A novel Recumbent Stepper 3-minute (RS 3Min) "all out" test may increase sensitivity of stress testing after stroke.

OBJECTIVE

To determine the feasibility of adding the RS 3Min test after GXT among persons after stroke.

DESIGN

A within-participant, nonrandomized, repeated measures design.

SETTING

Rehabilitation research laboratory and cardiovascular stress laboratory PARTICIPANTS: Fifteen participants with chronic stroke (56.7 ± 9.6 years; 6.4 ± 4.3 years post stroke; 8 male).

INTERVENTIONS

All participants randomly completed (1) a symptom-limited treadmill GXT and (2) a symptom-limited RS GXT followed by RS 3Min critical power test.

MAIN OUTCOME MEASURES

HR, ratings of perceived exertion, oxygen consumption, respiratory exchange ratio, and power output measured continuously during each test. Blood pressure measured every 2 minutes and or immediately post exercise. P value set at p < .05 from omnibus test for a significant difference among protocols.

RESULTS

The RS 3Min test had a significantly higher rate of achieving target HR compared to the RS GXT (9/14 vs 4/14, p = .02) and was not significantly different from the treadmill GXT (9/14 vs 5/14, p = .09). Minimum power output during the RS 3Min was significantly higher than peak power output during the RS GXT (110 ± 41 W vs. 84 ± 22 W, p = .02) with 12/15 participants reaching a VO2 plateau.

CONCLUSIONS

Although additional studies with randomized designs are needed, a novel RS 3Min "all out" test appears to be a promising method for enhancing test sensitivity in cardiovascular screening after stroke, while providing a potentially valid measure of critical power.

Determinants of daily physical activity limitation in patients with idiopathic pulmonary fibrosis

The purpose of the study was to determine the level of physical fitness assessed based on the physiological parameters and intensity of daily physical activity (PA) of patients with idiopathic pulmonary fibrosis (IPF). Additionally, we aimed to determine the intensity and duration of exercise that would bring beneficial modifications in the cardio-respiratory system of the patients with IPF. Eighteen patients with IPF (61.7 ± 4.3 years) and fifteen healthy volunteers performed a graded exercise test to exhaustion on a treadmill (Bruce protocol). Spirometry, dyspnea (mMRC, Borg scale) and fatigue (FAS) were measured. Total daily PA (kcal/day, MET) was monitored for seven days. The linear regression of PA (kcal/day) vs. peak oxygen uptake (%pred. peakVO2) was used to determine the intensity of daily PA that should be used in the rehabilitation of the patients with IPF. The average energy expenditure of daily PA of patients with IPF was 147.9 ± 86.4 kcal/day and it was significantly lower compared to healthy individuals. The linear regression indicated that the predicted energy expenditure of daily PA (PAEE) is 280.0 kcal/day, estimated based on VO2peak 100%pred. Therefore, the patients should add about 30 min of exercise of the intensity of 4.5 ± 0.2 kcal (calculated at the anaerobic threshold) or about 3700 steps/day to their daily PA. Diffusion for carbon monoxide and physiological variables of aerobic capacity seem to be the most important determinants of PA limitation in patients with IPF. The method of estimating PAEE should be used to plan training loads in IPF rehabilitation.

The efficacy of strength or aerobic exercise on quality of life and knee function in patients with knee osteoarthritis. A multi-arm randomized controlled trial with 1-year follow-up

OBJECTIVE

To evaluate the efficacy of strength exercise or aerobic exercise compared to usual care on knee-related quality of life (QoL) and knee function at 4 months and 1 year in individuals with knee osteoarthritis.

METHODS

A three-arm randomized controlled trial (RCT) compared 12 weeks of strength exercise or aerobic exercise (stationary cycling) to usual care supervised by physiotherapists in primary care. We recruited 168 participants aged 35-70 years with symptomatic knee osteoarthritis. The primary outcome was The Knee Injury and Osteoarthritis Outcome Score (KOOS) QoL at 1 year. Secondary outcomes were self-reported function, pain, and self-efficacy, muscle strength and maximal oxygen uptake (VO2max) at 4 months and 1 year.

RESULTS

There were no differences between strength exercise and usual care on KOOS QoL (6.5, 95% CI -0.9 to 14), or for aerobic exercise and usual care (5.0, 95% CI -2.7 to 12.8), at 1 year. The two exercise groups showed better quadriceps muscle strength, and VO2max at 4 months, compared to usual care.

CONCLUSION

This trial found no statistically significant effects of two exercise programs compared to usual care on KOOS QoL at 1 year in individuals with symptomatic and radiographic knee osteoarthritis, but an underpowered sample size may explain lack of efficacy between the intervention groups and the usual care group.

CLINICALTRIALS

GOV IDENTIFIER

NCT01682980.

Acute Physiological and Perceptual Responses to Whole-Body High-Intensity Interval Training Compared with Equipment-Based Interval and Continuous Training

Low-volume, time-efficient high-intensity interval training (HIIT), which involves whole-body (WB) callisthenics exercises, has gained worldwide popularity in recent years. However, the physiological and perceptual impact of WB-HIIT in comparison to specialised, equipment-based training is relatively less studied. This study compared the acute physiological and perceptual responses to a single session of WB-HIIT, ergometer-based HIIT (ERG-HIIT) and conventional moderate-intensity continuous training (MICT). Fourteen physically inactive adults (age: 28.4 ± 6.5 years, VO2peak: 31.0 ± 6.2 mL· kg-1· min-1) underwent three main trials (WB-HIIT: 12 x 30-s high-intensity callisthenics workout; ERG: HIIT: 12 x 30-s high-intensity cycling bouts; MICT: 30-min cycling at 50% peak power output) in a randomized cross-over order 3-7 days apart. The mean session heart rate (HR) and perceived exertion were comparable across all three protocols (p > 0.05). WB-HIIT attained a similar peak HR (87.4 ± 9.4 %HRmax) as that of ERG-HIIT (83.0 ± 8.6 %HRmax), and significantly greater than that of MICT (78.7 ± 5.5 %HRmax, p = 0.001). However, WB-HIIT induced significantly higher blood lactate levels (7.2 ± 1.8 mmol/L) compared to both ERG-HIIT (5.1 ± 1.3 mmol/L, p < 0.05) and MICT (3.1 ± 1.5 mmol/L, p < 0.001). The participants reported higher self-efficacy and greater enjoyment with WB-HIIT compared to MICT (p < 0.05). The mean HR and perceived exertion responses to WB-HIIT are comparable to those of equipment-based HIIT and MICT; however, WB-HIIT results in greater metabolic strain than both other modalities. Despite this, the overall perceptual responses to WB-HIIT are positive, suggesting that it could be a viable exercise alternative, especially for individuals with limited exercise time and restricted access to facilities and equipment.

Effects of Controlled Supramaximal High-Intensity Interval Training on Cardiorespiratory Fitness and Global Cognitive Function in Older Adults: The Umeå HIT Study-A Randomized Controlled Trial

BACKGROUND

This study examined the effects of regulated and controlled supramaximal high-intensity interval training (HIT) adapted for older adults, compared to moderate-intensity training (MIT), on cardiorespiratory fitness; cognitive, cardiovascular, and muscular function; and quality of life.

METHODS

Sixty-eight nonexercising older adults (66-79 years, 44% males) were randomized to 3 months of twice-weekly HIT (20-minute session including 10 × 6-second intervals) or MIT (40-minute session including 3 × 8-minute intervals) on stationary bicycles in an ordinary gym setting. Individualized target intensity was watt controlled with a standardized pedaling cadence and individual adjustment of the resistance load. Primary outcomes were cardiorespiratory fitness (V̇o2peak) and global cognitive function (unit-weighted composite).

RESULTS

V̇o2peak increased significantly (mean 1.38 mL/kg/min, 95% CI [0.77, 1.98]), with no between-group difference (mean difference 0.05 [-1.17, 1.25]). Global cognition did not improve (0.02 [-0.05, 0.09]), nor differed between groups (0.11 [-0.03, 0.24]). Significant between-group differences in change were observed for working memory (0.32 [0.01, 0.64]), and maximal isometric knee extensor muscle strength (0.07 N·m/kg [0.003, 0.137]), both in favor of HIT. Irrespective of the group, there was a negative change in episodic memory (-0.15 [-0.28, -0.02]), a positive change in visuospatial ability (0.26 [0.08, 0.44]), and a decrease in systolic (-2.09 mmHg [-3.54, -0.64]) and diastolic (-1.27 mmHg [-2.31, -0.25]) blood pressure.

CONCLUSIONS

In nonexercising older adults, 3 months of watt-controlled supramaximal HIT improved cardiorespiratory fitness and cardiovascular function to a similar extent as MIT, despite half the training time. In favor of HIT, there was an improvement in muscular function and a potential domain-specific effect on working memory.

CLINICAL TRIAL REGISTRATION

NCT03765385.

How little is enough? The feasibility of conducting a dose-escalation study for exercise training in people with stroke

QUESTION

Is it feasible and safe to conduct an exercise dose-finding study in people with stroke? Is it possible to determine a minimal dose of exercise required to see clinically meaningful improvements in cardiorespiratory fitness?

METHODS

Dose-escalation study. Twenty people with stroke (n=5 per cohort) who were able to walk independently participated in home-based, telehealth-supervised aerobic exercise sessions 3 d/week at moderate-vigorous intensity for 8 weeks. Dose parameters of frequency (3 d/week), intensity (55-85% of heart rate peak) and program length (8 weeks) were kept constant. The duration of exercise sessions was increased by 5 min per session from Dose 1 (10 min/session) to Dose 4 (25 min/session). Doses were escalated if safe and tolerable (< 33% of a cohort reaching a dose-limiting threshold). Doses were efficacious if ≥ 67% of a cohort increased peak oxygen consumption ≥ 2mL/kg/min.

RESULTS

Target exercise doses were well adhered to, and the intervention was safe (480 exercise sessions delivered; one fall resulting in minor laceration) and tolerable (no participants met the dose-limiting threshold). None of the exercise doses met our criterion for efficacy.

CONCLUSIONS

It is possible to conduct a dose-escalation trial for people with stroke. The small cohort sizes may have limited the ability to determine an efficacious minimum dose of exercise. Providing supervised exercise session at these prescribed doses via telehealth was safe.

REGISTRATION

The study was registered with the Australian New Zealand Clinical Trials Registry (ACTRN12617000460303).