Acute effects of commercial energy drink consumption on exercise performance and cardiovascular safety: a randomized, double-blind, placebo-controlled, crossover trial

The aim of this study was to examine the acute effects of a non-caloric energy drink (C4E) compared to a traditional sugar-containing energy drink (MED) and non-caloric placebo (PLA) on exercise performance and cardiovascular safety. Thirty healthy, physically active males (25 ± 4 y) completed three experimental visits under semi-fasted conditions (5-10 h) and in randomized order, during which they consumed C4E, MED, or PLA matched for volume, appearance, taste, and mouthfeel. One hour after drink consumption, participants completed a maximal, graded exercise test (GXT) with measurement of pulmonary gases, an isometric leg extension fatigue test (ISOFTG), and had their cardiac electrical activity (ECG), leg blood flow (LBF), and blood pressure (BP) measured throughout the visit. Neither MED nor C4E had an ergogenic effect on maximal oxygen consumption, time to exhaustion, or peak power during the GXT (p > 0.05). Compared to PLA, MED reduced fat oxidation (respiratory exchange ratio (RER) +0.030 ± 0.01; p = 0.026) during the GXT and did not influence ISOFTG performance. Compared to PLA, C4E did not alter RER (p = 0.94) and improved impulse during the ISOFTG (+0.658 ± 0.25 V·s; p = 0.032). Relative to MED, C4E did not significantly improve gas exchange threshold (p = 0.05-0.07). Both MED and C4E increased systolic BP at rest (+7.1 ± 1.2 mmHg; p < 0.001 and + 5.7 ± 1.0 mmHg; p < 0.001, respectively), C4E increased SBP post-GXT (+13.3 ± 3.8 mmHg; p < 0.001), and MED increased SBP during recovery (+3.2 ± 1.1 mmHg; p < 0.001). Neither MED nor C4E influenced ECG measures (p ≥ 0.08) or LBF (p = 0.37) compared to PLA. C4E may be more efficacious for improving performance in resistance-type tasks without altering fat oxidation under semi-fasted conditions during fatiguing exercise bouts, but promotes similar changes in BP and HR to MED.

Hemodynamic and Metabolic Responses to Moderate and Vigorous Cycle Ergometry in Men Who Have Had Transtibial Amputation

Adults who have had an amputation face barriers to having an active lifestyle which attenuates cardiorespiratory fitness. Prior studies in amputees typically involve treadmill walking or arm ergometry, yet physiological responses to bilateral leg cycling are less understood. This study assessed the hemodynamic and metabolic responses to moderate and vigorous cycle ergometry in men who have had a transtibial amputation (TTA). Five men who had had a unilateral TTA (age = 39 ± 15 yr) and six controls (CONs) without an amputation (age = 31 ± 11 yr) performed two 20 min bouts of cycling differing in intensity. Cardiac output (CO), stroke volume (SV), and oxygen consumption (VO2) were measured during moderate intensity continuous exercise (MICE) and high intensity interval exercise (HIIE) using thoracic impedance and indirect calorimetry. In response to MICE and HIIE, the HR and VO2 levels were similar (p > 0.05) between groups. Stroke volume and CO were higher (p < 0.05) in the CONs, which was attributed to their higher body mass. In men with TTAs, HIIE elicited a peak HR = 88%HRmax and substantial blood lactate accumulation, representing vigorous exercise intensity. No adverse events were exhibited in the men with TTAs. The men with TTAs show similar responses to MICE and HIIE versus the CONs.

High-intensity interval training improves respiratory and cardiovascular adjustments before and after initiation of exercise

Purpose: High-intensity interval training (HIIT) may induce training-specific physiological adaptations such as improved respiratory and cardiovascular adjustments before and after the onset of high-intensity exercise, leading to improved exercise performance during high-intensity exercise. The present study investigated the effects of HIIT on time-dependent cardiorespiratory adjustment during maximal exercise and before and after initiation of high-intensity exercise, as well as on maximal exercise performance. Methods: 21 healthy male college students were randomly assigned to HIIT group (n = 11) or control group (n = 10). HIIT group performed training on a cycle ergometer once a week for 8 weeks. The training consisted of three bouts of exercise at 95% maximal work rate (WRmax) until exhaustion. Before and after the HIIT program, dynamic cardiorespiratory function was investigated by ramp and step exercise tests, and HIIT-induced cardiac morphological changes were assessed using echocardiography. Results: HIIT significantly improved not only maximal oxygen uptake and minute ventilation, but also maximal heart rate (HR), systolic blood pressure (SBP), and time to exhaustion in both exercise tests (p < 0.05). Time-dependent increases in minute ventilation (VE) and HR before and at the start of exercise were significantly enhanced after HIIT. During high-intensity exercise, there was a strong correlation between percent change (from before to after HIIT program) in time to exhaustion and percent change in HRmax (r = 0.932, p < 0.001). Furthermore, HIIT-induced cardiac morphological changes such as ventricular wall hypertrophy was observed (p < 0.001). Conclusion: We have demonstrated that HIIT at 95% WRmax induces training-specific adaptations such as improved cardiorespiratory adjustments, not only during maximal exercise but also before and after the onset of high-intensity exercise, improvement of exercise performance mainly associated with circulatory systems.

Effects of pre-exercise intake of plant- and animal-based foods on arterial function and aerobic exercise capacity in healthy young men: a randomized cross-over trial

The purpose of this study was to examine the effects of plant- versus animal-based food intake before exercise on arterial function and subsequent aerobic exercise capacity. Eleven healthy adult males (mean age, 22.6 ± 1.8 years) participated in this study. A plant- or animal-based randomized meal type crossover comparison was conducted on separate days with a uniform protein, fat, and carbohydrate balance. Both carotid-femoral pulse wave velocity (cfPWV), femoral-ankle pulse wave velocity (faPWV), and brachial artery flow-mediated dilatation (FMD) were measured as indexes of aortic and peripheral arterial stiffness and vascular endothelial function, respectively, before and at 120 min after the meal. After these measurements, maximal oxygen uptake was assessed using a graded power test on an electronically braked cycle ergometer. The results revealed that cfPWV was significantly lower, whereas FMD was significantly higher, at 120 min after compared with before the plant-based meal (p = 0.01 and 0.02, respectively). By contrast, cfPWV and FMD did not change at 120 min after compared with before the animal-based meal. In addition, faPWV did not change at 120 min after compared with before the meal for either meal type. Maximal oxygen uptake was higher in the plant- than in the animal-based meal type (p = 0.02). These results suggest that pre-exercise plant-based food intake may improve central arterial stiffness and vascular endothelial function, which may have favorable implications for aerobic exercise capacity.

Including supramaximal verification reduced uncertainty in VO2peak response rate

Many reports describe using a supramaximal verification phase-exercising at a power output higher than the highest power output recorded during an incremental cardiopulmonary test-to validate VO2max. The impact of verification phases on estimating the proportion of individuals who increased VO2peak in response to high-intensity interval training (HIIT) remains an underexplored area in the individual response literature. This analysis investigated the influence of same-day and separate-day verification phases during repeated measurements (incremental tests-INCR1 and INCR2; incremental tests + supramaximal verification phases-INCR1+ and INCR2+) of VO2peak on typical error (TE) and the proportion of individuals classified as responders (i.e., the response rate) following 4 weeks of HIIT (n = 25) or a no-exercise control period (n = 9). Incorporation of supramaximal verification consistently reduced the standard deviation of individual response, TE, and confidence interval (CI) widths. However, variances were statistically similar across all groups (p > 0.05). Response rates increased when incorporating either one (INCR1 to INCR1+; 24%-48%, p = 0.07) or two (INCR2 to INCR2+; 28%-48%, p = 0.063) supramaximal verification phases. However, response rates remained unchanged when either zero-based thresholds or smallest worthwhile difference response thresholds were used (50% and 90% CIs, all p > 0.05). Supramaximal verification phases reduced random variability in VO2peak response to HIIT. Compared with separate-day testing (INCR2 and INCR2+), the incorporation of a same-day verification (INCR1+) reduced CI widths the most. Researchers should consider using a same-day verification phase to reduce uncertainty and better estimate VO2peak response rate to HIIT.

The Effects of a Supramaximal Intermittent Training Program on Aerobic and Anaerobic Running Measures in Junior Male Soccer Players

This study investigated the effectiveness of supplementing regular preseason soccer training with a supramaximal intermittent shuttle-run training (ISRT) model prescribed from Carminatti's Test peak speed (PST-CAR) in aerobic performance-related indices and sprinting speed in male junior soccer players. Twenty-three national-level soccer players (mean ± SD; age 18.07 ± 0.9 y, body height 1.76 ± 0.65 m, body mass 71.9 ± 8.7 kg) were assigned to either an experimental group (EG; n = 13) performing ISRT + soccer training or a control group (CG; n = 10) that followed regular preseason soccer training alone. The following tests were applied before and after the eight-week training intervention: (i) incremental treadmill tests (VO2max and lactate minimum speed - LMS); (ii) linear 30-m sprint test and Carminatti's Test (PST-CAR). Results indicated larger gains for the EG in LMS (Δ = 9.53% vs. 2.82%) and PST-CAR (Δ = 5.50% vs. 2.10%) than in the CG. Furthermore, changes in VO2max produced higher effect size (d) values for the EG (Δ = 6.67%; d = 0.59) than the CG (Δ = 1.88%; d = 0.18). Both groups improved (p = 0.002) their flying 20-m sprint speed (EG: Δ = 1.01%; CG: Δ = 1.56%). However, small decreases were observed for 10-m sprint speed in the CG (Δ = -2.19%; d = -0.44), while only trivial changes were noticed for the EG (Δ = -0.50%; d = -0.16). Our data support that additional supramaximal ISRT is an effective training stimulus to enhance aerobic performance-related indices and promote small improvements in maximal running speed without impairing the soccer players' acceleration capacity. This study also shows that PST-CAR can be useful for individualizing running intensity in supramaximal ISRT modes.

Sedentarism in Recreational Marathon Runners

Aim

Although it has been previously observed that sedentary behavior (SB) was not related to training duration in marathon runners, little information existed about the relationship of SB with training, anthropometric and physiological characteristics in this population. This study aimed to investigate the prevalence of SB and its correlation with performance parameters (such as body fat percentage, maximal oxygen uptake and weekly training volume) as well as its variation by sex and day (ie, weekdays versus weekend) in recreational marathon runners.

Methods

A total of 151 finishers (women, n = 29; men, n = 122; age 43.1 (8.7) years, mean (standard deviation)) in the Athens marathon 2017 performed a series of anthropometric and physiological tests, and completed the Multi-context sitting time questionnaire.

Results

SB did not correlate with anthropometric and physiological characteristics and no difference in these characteristics was shown between low and high sedentary participants (p > 0.05). SB did not differ between women and men (p > 0.05), but differed between working and non-working days (p < 0.05).

Conclusion

In contrast to previous findings on the general population indicating an association of a high SB with a low cardiorespiratory and muscular fitness, our finding of no correlation between SB and physical fitness in marathon runners suggested that endurance exercise might offset the negative effects of SB.

Predictors of Long-COVID and Chronic Impairment of Exercise Tolerance in Spiroergometry in Patients after 15 Months of COVID-19 Recovery

BACKGROUND

The aim of the study was to identify factors that may cause the presence of long COVID and to assess factors that affect chronic limited exercise tolerance in spiroergometry after one-year follow-up in patients who had recovered from COVID-19.

METHODS

Of 146 patients hospitalised in the Cardiology Department, 82 completed a one-year follow-up (at least 15 months post-COVID-19 recovery). We compared their conditions at initial screening and follow-up to analyse the course of long COVID and exercise intolerance mechanisms. Clinical examinations, laboratory tests, echocardiography, cardiopulmonary exercise testing, and body composition analysis were performed.

RESULTS

The patients, after one-year follow-up, had significantly higher levels of high-sensitivity cardiac troponin T (hs-cTnT) (p = 0.03), left atrium diameter (LA) (p = 0.03), respiratory exchange ratio (RER) (p = 0.008), and total body water content percentage (TBW%) (p < 0.0001) compared to the 3-month assessment. They also had lower forced vital capacity in litres (FVC) (p = 0.02) and percentage (FVC%) (p = 0.001). The factors independently associated with a decline in maximum oxygen uptake (VO2max) after one-year follow-up included the percentage of fat (OR 2.16, 95% CI: 0.51-0.77; p = 0.03), end-diastolic volume (EDV) (OR 2.38, 95% CI 0.53-0.78; p = 0.02), and end-systolic volume (ESV) (OR 2.3, 95% CI: 0.52-0.78; p = 0.02).

CONCLUSIONS

Higher left ventricular volumes and fat content (%) were associated with a reduced peak VO2max when assessed 15 months after COVID-19 recovery.

Effect of vitamin D3 supplementation in winter on physical performance of university students: a one-month randomized controlled trial

BACKGROUND

There is epidemiological evidence which suggests an association between 25-hydroxyvitamin D [25(OH)D] levels and bone and muscle function; however, it is unclear whether vitamin D supplementation has an added benefit beyond bone health. Here, we investigated the effects of vitamin D3 supplementation (1 month) on physical performance in Chinese university students in winter.

METHODS

One hundred and seventeen eligible subjects with 25(OH)D (19.2 ± 7.8 ng/mL) were randomly assigned to either vitamin D3 supplement (N = 56; 1000 IU/day) or the control (N = 61) group for 1 month. Pre- and post-measurements included: 1) serum levels of 25(OH)D; 2) musculoskeletal and pulmonary function [vertical jump height (VJH) and right handgrip strength (RHS), forced vital capacity (FVC), and forced expiratory volume at 1s (FEV1)]; 3) bone turnover markers [parathyroid hormone (PTH), n-terminal osteocalcin (N-MID), and calcium]; 4) hemoglobin-related parameters [hemoglobin (Hb), hematocrit (HCT), red blood cells (RBC), and red cell distribution width (RDW)]; 5) lipid parameters [total triglycerides (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C)]; 6) Fatigue-related indicators [serum creatine kinase (CK), lactate dehydrogenase (LDH), and total testosterone (T)]. In addition, aerobic capacity was assessed by measuring maximal oxygen uptake (VO2max) at baseline.

RESULTS

During wintertime, supplementation with 1000 IU/d of vitamin D3 significantly increased serum 25(OH)D levels (from 18.85 ± 7.04 to 26.98 ± 5.88 ng/mL, p < 0.05), accompanied by a decrease of PTH (p < 0.05). However, vitamin D3 supplementation did not significantly impact the physical performance, serum lipid parameters, and bone turnover markers of students. Furthermore, 25(OH)D was found to be positively correlated with VJH and negatively correlated with PTH and TC at the beginning and end of the study (p < 0.05). In addition, the multiple linear regression analysis showed that 25(OH)D combined with athletic, gender, height, weight, Hb, and FVC could account for 84.0% of the VO2max value.

CONCLUSIONS

The study demonstrated that one-month of 1000 IU/d of vitamin D3 supplementation during the winter had beneficial effects on 25(OH)D status and PTH. However, vitamin D3 intervention was not sufficient to improve physical performance. Furthermore, 25(OH)D levels combined with athletic, Hb and FVC could be a predictor of VO2max.

Development and Interplay of Metabolic and Mechanical Performance Determinants Over an Annual Training Period in Adolescent National-Level Squad Swimmers

PURPOSE

The study examined the longitudinal interplay of anthropometric, metabolic, and neuromuscular development related to performance in adolescent national-level swimmers over 12 months.

METHODS

Seven male and 12 female swimmers (14.8 [1.3] y, FINA [International Swimming Federation] points 716 [51]) were tested before (T0) and after the preparation period (T1), at the season's peak (T2), and before the next season (T3). Anthropometric (eg, fat percentage) and neuromuscular parameters (squat and bench-press load-velocity profile) were assessed on dry land. Metabolic (cost of swimming [C], maximal oxygen uptake [V˙O2peak], and peak blood lactate [bLapeak]) and performance (sprinting speed [vsprint] and lactate thresholds [LT1 and 2]) factors were determined using a 500-m submaximal, 200-m all-out, 20-second sprint, and incremental test (+0.03 m·s-1, 3 min), respectively, in front-crawl swimming.

RESULTS

vsprint (+0.6%) and LT1 and 2 (+1.9-2.4%) increased trivially and slightly, respectively, from T0 to T2 following small to moderate strength increases (≥+10.2%) from T0 to T1 and V˙O2peak (+6.0%) from T1 to T2. Bench-press maximal strength and peak power correlated with vsprint from T0 to T2 (r ≥ .54, P < .05) and LT2 at T1 (r ≥ .47, P < .05). Changes in fat percentage and V˙O2peak (T2-T1 and T3-T2, r ≤ -.67, P < .01) and C and LT2 (T2-T0, r = -.52, P = .047) were also correlated.

CONCLUSIONS

Increases in strength and V˙O2peak from preparation to the competition period resulted in improved sprint and endurance performance. Across the season, upper-body strength was associated with vsprint and LT2, although their changes were unrelated.

Aerobic high-intensity intervals improve V̇O2max more than supramaximal sprint intervals in females, similar to males

INTRODUCTION

Maximal oxygen uptake (V̇O2max ) is a pivotal factor for aerobic endurance performance. Recently, aerobic high-intensity interval training (HIIT) was documented to be superior to sprint interval training (SIT) in improving V̇O2max in well-trained males. However, as mounting evidence suggests that physiological responses to training are sex-dependent, examining the effects of HIIT versus SIT on V̇O2max , anaerobic capacity, and endurance performance in females is warranted.

METHODS

We randomized 81 aerobically well-trained females (22 ± 2 years, 51.8 ± 3.6 mL∙kg-1 ∙min-1 V̇O2max ), training three times weekly for 8 weeks, to well-established protocols: (1) HIIT 4 × 4 min at ~95% of maximal aerobic speed (MAS), with 3 min active recovery (2) SIT 8 × 20 s at ~150% of MAS, with 10 s passive recovery (3) SIT 10 × 30 s at ~175% of MAS, with 3.5 min active recovery.

RESULTS

Only HIIT 4 × 4 min increased V̇O2max (7.3 ± 3.1%), different from both SIT groups (all p < 0.001). Anaerobic capacity (maximal accumulated oxygen deficit) increased following SIT 8 × 20 s (6.5 ± 10.5%, p < 0.05), SIT 10 × 30 s (14.4 ± 13.7%, p < 0.05; different from HIIT 4 × 4 min, p < 0.05). SIT 10 × 30 s resulted in eight training-induced injuries, different from no injuries following HIIT 4 × 4 min and SIT 8 × 20 s (p < 0.001). All groups improved long-distance (3000-meter) and sprint (300-meter) running performance (all p < 0.001). SIT protocols improved sprint performance more than HIIT 4 × 4 min (p < 0.05). Compared to previous male results, no increase in V̇O2max following SIT 8 × 20 s (p < 0.01), and a higher injury rate for SIT 10 × 30 s (p < 0.001), were evident.

CONCLUSIONS

In aerobically well-trained women, HIIT is superior to SIT in increasing V̇O2max while all-out treadmill running SIT is potentially more harmful.

Lifestyle Behaviours, Self-Esteem and Academic Performance in Primary Education Students-A Structural Equation Model According to Sex and School Type

(1) Background: The present study aimed to examine the relationship between physical activity (PA), screen time (ST), maximal oxygen uptake (VO2max), Mediterranean diet (MD) adherence, self-esteem (SE) and academic performance (AP) in primary education students. In order to address this aim, an explanatory model was developed to examine the existing relationships between PA, ST, VO2max, MD adherence, SE and AP. Further, the proposed structural model was examined via multi-group analysis as a function of sex and school type. (2) Methods: A non-experimental, descriptive, comparative and cross-sectional study was designed with a total sample of 269 Spanish students (11.29 ± 0.62). Validated questionnaires were administered to collect data on study variables. (3) Results: Relative to boys, girls reported better academic grades and showed a stronger positive relationship between MD adherence and AP, MD adherence and PA, and VO2max and SE. Likewise, girls showed a stronger negative relationship between ST and VO2max, and ST and MD adherence. At the same time, mixed funding school (MFS) students reported higher PA engagement than state school (SS) students. However, SS students reported better MD adherence, ST and AP than MFS students. Further, a stronger positive relationship was found in SS students between MD adherence or VO2max and SE than in MFS students. Also, within the former group, ST was more negatively related to MD adherence and VO2max. (4) Conclusions: Scientific and educational communities must develop future strategies that consider potential determinants in order to target more desirable outcomes.

To what extent do physiological tolerances determine elevational range limits of mammals?

A key question in biology concerns the extent to which distributional range limits of species are determined by intrinsic limits of physiological tolerance. Here, we use common-garden data for wild rodents to assess whether species with higher elevational range limits typically have higher thermogenic capacities in comparison to closely related lowland species. Among South American leaf-eared mice (genus Phyllotis), mean thermogenic performance is higher in species with higher elevational range limits, but there is little among-species variation in the magnitude of plasticity in this trait. In the North American rodent genus Peromyscus, highland deer mice (Peromyscus maniculatus) have greater thermogenic maximal oxygen uptake (V ̇ O 2 max ${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ ) than lowland white-footed mice (Peromyscus leucopus) at a level of hypoxia that matches the upper elevational range limit of the former species. In highland deer mice, the enhanced thermogenicV ̇ O 2 max ${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ in hypoxia is attributable to a combination of evolved and plastic changes in physiological pathways that govern the transport and utilization of O2 and metabolic substrates. Experiments with Peromyscus mice also demonstrate that exposure to hypoxia during different stages of development elicits plastic changes in cardiorespiratory traits that improve thermogenicV ̇ O 2 max ${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ via distinct physiological mechanisms. Evolved differences in thermogenic capacity provide clues about why some species are able to persist in higher-elevation habitats that lie slightly beyond the tolerable limits of other species. Such differences in environmental tolerance also suggest why some species might be more vulnerable to climate change than others.

Mean power output for muscular endurance exercises and maximal oxygen uptake in military young adults

The American Heart Association recommends a cardiopulmonary exercise test (CPET) and some alternative exercise tests to evaluate maximal oxygen uptake (VO2 max) of youth. Power output has shown a high correlation with VO2 max on a CPET. However, the correlations between mean power output (MPO) for muscular endurance exercises and VO2 max measured from a CPET are not established in young adults. Forty-five volunteers, with an average age of 29.93 ± 7.05 years, from a sample of 1120 military personnel in Taiwan who attended a 2-minute pushup test and a 2-minute sit-up test were included in the current study. These volunteers subsequently underwent a CPET using the Bruce protocol to assess VO2 max. According to the physics rule, MPO (watts) for the muscular endurance test was defined as a product of moving distance and force: [1/5 × body height (m) × numbers performed × body mass (kg) × gravity (9.8 m/s2)]. Pearson correlation analyses were performed. For the 2-min pushups, the correlations (r) between pushup numbers and VO2 max with and without body mass adjustment were 0.541 (P < .01) and 0.188 (P = .21), respectively, while the correlation (r) between MPO and VO2 max with and without body mass adjustment were 0.410 and 0.557 (both P < .01), respectively. For the 2-minute sit-ups, the correlations (r) between sit-up numbers and VO2 max with and without body mass adjustment were 0.529 (P < .01) and 0.291 (P = .052), respectively, while the correlations (r) between MPO and VO2 max with and without body mass adjustment were 0.318 (P = .03) and 0.705 (P < .01), respectively. In military young adults, MPO for both the 2-minute sit-up and the 2-minute pushup tests could be used as alternative field-based methods to estimate VO2 max.

Prediction of Exercise Tolerance in the Severe and Extreme Intensity Domains by a Critical Power Model

This study aimed to assess the predictive capability of different critical power (CP) models on cycling exercise tolerance in the severe- and extreme-intensity domains. Nineteen cyclists (age: 23.0 ± 2.7 y) performed several time-to-exhaustion tests (Tlim) to determine CP, finite work above CP (W'), and the highest constant work rate at which maximal oxygen consumption was attained (IHIGH). Hyperbolic power-time, linear power-inverse of time, and work-time models with three predictive trials were used to determine CP and W'. Modeling with two predictive trials of the CP work-time model was also used to determine CP and W'. Actual exercise tolerance of IHIGH and intensity 5% above IHIGH (IHIGH+5%) were compared to those predicted by all CP models. Actual IHIGH (155 ± 30 s) and IHIGH+5% (120 ± 26 s) performances were not different from those predicted by all models with three predictive trials. Modeling with two predictive trials overestimated Tlim at IHIGH+5% (129 ± 33 s; p = 0.04). Bland-Altman plots of IHIGH+5% presented significant heteroscedasticity by all CP predictions, but not for IHIGH. Exercise tolerance in the severe and extreme domains can be predicted by CP derived from three predictive trials. However, this ability is impaired within the extreme domain.

Physiological characteristics and performance of a world-record breaking tower runner

This study reports the physiological and performance profiles of a world-class tower runner during a 6-week period surrounding a successful Guinness World Record (WR) attempt, and discusses the efficacy of a tower running specific field test. The world-ranked number 2 tower runner completed four exercise tests [laboratory treadmill assessment (3 weeks before the WR attempt), familiarisation to a specific incremental tower running field test (1 week before), tower running field test (1 week after), and tower running time trial (TT) (3 weeks after)] and the WR attempt within 6-week period. Peak oxygen consumption (VO₂peak) during the laboratory test, field test, and TT were 73.3, 75.5 and 78.3 mL·kg^-1·min^-1, respectively. The VO₂ corresponding to the second ventilatory threshold was 67.3 mL·kg^-1·min^-1 (89.1% of VO₂peak), identified at stage 4 (tempo; 100 b·min^-1), during the field test. The duration of the TT was 10 min 50 s, with an average VO₂ of 71.7 mL·kg^-1·min^-1 (91.6% of VO₂peak), HR of 171 b·min^-1 (92% of peak HR), vertical speed of 0.47 m·s^-1, and cadence was 117 steps·min^-1. A world-class tower runner possesses a well-developed aerobic capacity. A specific, field-based test revealed greater VO₂peak than a laboratory test, indicating a need for sport-specific testing procedures.

Hemoglobin mass and performance responses during 4 weeks of normobaric "live high-train low and high"

PURPOSE

To investigate whether 4 weeks of normobaric "live high-train low and high" (LHTLH) causes different hematological, cardiorespiratory, and sea-level performance changes compared to living and training in normoxia during a preparation season.

METHODS

Nineteen (13 women, 6 men) cross-country skiers competing at the national or international level completed a 28-day period (∼18 h day^-1 ) of LHTLH in normobaric hypoxia of ∼2400 m (LHTLH group) including two 1 h low-intensity training sessions per week in normobaric hypoxia of 2500 m while continuing their normal training program in normoxia. Hemoglobin mass (Hb_mass ) was assessed using a carbon monoxide rebreathing method. Time to exhaustion (TTE) and maximal oxygen uptake (VO_2max ) were measured using an incremental treadmill test. Measurements were completed at baseline and within 3 days after LHTLH. The control group skiers (CON) (seven women, eight men) performed the same tests while living and training in normoxia with ∼4 weeks between the tests.

RESULTS

Hb_mass in LHTLH increased 4.2 ± 1.7% from 772 ± 213 g (11.7 ± 1.4 g kg^-1 ) to 805 ± 226 g (12.5 ± 1.6 g kg^-1 ) (p < 0.001) while it was unchanged in CON (p = 0.21). TTE improved during the study regardless of the group (3.3 ± 3.4% in LHTLH; 4.3 ± 4.8% in CON, p < 0.001). VO_2max did not increase in LHTLH (61.2 ± 8.7 mL kg^-1  min^-1 vs. 62.1 ± 7.6 mL kg^-1  min^-1 , p = 0.36) while a significant increase was detected in CON (61.3 ± 8.0-64.0 ± 8.1 mL kg^-1  min^-1 , p < 0.001).

CONCLUSIONS

Four-week normobaric LHTLH was beneficial for increasing Hb_mass but did not support the short-term development of maximal endurance performance and VO_2max when compared to the athletes who lived and trained in normoxia.

Nonexercise machine learning models for maximal oxygen uptake prediction in national population surveys

OBJECTIVE

Nonexercise algorithms are cost-effective methods to estimate cardiorespiratory fitness (CRF), but the existing models have limitations in generalizability and predictive power. This study aims to improve the nonexercise algorithms using machine learning (ML) methods and data from US national population surveys.

MATERIALS AND METHODS

We used the 1999-2004 data from the National Health and Nutrition Examination Survey (NHANES). Maximal oxygen uptake (VO2 max), measured through a submaximal exercise test, served as the gold standard measure for CRF in this study. We applied multiple ML algorithms to build 2 models: a parsimonious model using commonly available interview and examination data, and an extended model additionally incorporating variables from Dual-Energy X-ray Absorptiometry (DEXA) and standard laboratory tests in clinical practice. Key predictors were identified using Shapley additive explanation (SHAP).

RESULTS

Among the 5668 NHANES participants in the study population, 49.9% were women and the mean (SD) age was 32.5 years (10.0). The light gradient boosting machine (LightGBM) had the best performance across multiple types of supervised ML algorithms. Compared with the best existing nonexercise algorithms that could be applied to the NHANES, the parsimonious LightGBM model (RMSE: 8.51 ml/kg/min [95% CI: 7.73-9.33]) and the extended LightGBM model (RMSE: 8.26 ml/kg/min [95% CI: 7.44-9.09]) significantly reduced the error by 15% and 12% (P < .001 for both), respectively.

DISCUSSION

The integration of ML and national data source presents a novel approach for estimating cardiovascular fitness. This method provides valuable insights for cardiovascular disease risk classification and clinical decision-making, ultimately leading to improved health outcomes.

CONCLUSION

Our nonexercise models provide improved accuracy in estimating VO2 max within NHANES data as compared to existing nonexercise algorithms.

The Impact of Acetazolamide and Methazolamide on Exercise Performance in Normoxia and Hypoxia

Doherty, Connor J., Jou-Chung Chang, Benjamin P. Thompson, Erik R. Swenson, Glen E. Foster, and Paolo B. Dominelli. The impact of acetazolamide and methazolamide on exercise performance in normoxia and hypoxia. High Alt Med Biol. 24:7-18, 2023.-Carbonic anhydrase (CA) inhibitors are commonly prescribed for acute mountain sickness (AMS). In this review, we sought to examine how two CA inhibitors, acetazolamide (AZ) and methazolamide (MZ), affect exercise performance in normoxia and hypoxia. First, we briefly describe the role of CA inhibition in facilitating the increase in ventilation and arterial oxygenation in preventing and treating AMS. Next, we detail how AZ affects exercise performance in normoxia and hypoxia and this is followed by a discussion on MZ. We emphasize that the overarching focus of the review is how the two drugs potentially affect exercise performance, rather than their ability to prevent/treat AMS per se, their interrelationship will be discussed. Overall, we suggest that AZ hinders exercise performance in normoxia, but may be beneficial in hypoxia. Based upon head-to-head studies of AZ and MZ in humans on diaphragmatic and locomotor strength in normoxia, MZ may be a better CA inhibitor when exercise performance is crucial at high altitude.

Maximum Heart Rate- and Lactate Threshold-Based Low-Volume High-Intensity Interval Training Prescriptions Provide Similar Health Benefits in Metabolic Syndrome Patients

Exercise is an integral part of metabolic syndrome (MetS) treatment. Recently, low-volume high-intensity interval training (LOW-HIIT) has emerged as a time-efficient approach to improving cardiometabolic health. Intensity prescriptions for LOW-HIIT are typically based on maximum heart rate (HR_max) percentages. However, HR_max determination requires maximal effort during exercise testing, which may not always be feasible/safe for MetS patients. This trial compared the effects of a 12-week LOW-HIIT program based on: (a) HR_max (HIIT-HR), or (b) submaximal lactate threshold (HIIT-LT), on cardiometabolic health and quality of life (QoL) in MetS patients. Seventy-five patients were randomized to HIIT-HR (5 × 1 min at 80-95% HR_max), HIIT-LT (5 × 1 min at 95-105% LT) groups, both performed twice weekly on cycle ergometers, or a control group (CON). All patients received nutritional weight loss consultation. All groups reduced their body weight (HIIT-HR: -3.9 kg, p < 0.001; HTT-LT: -5.6 kg, p < 0.001; CON: -2.6 kg, p = 0.003). The HIIT-HR and HIIT-LT groups similarly, improved their maximal oxygen uptake (+3.6 and +3.7 mL/kg/min, p < 0.001), glycohemoglobin (-0.2%, p = 0.005, and -0.3%, p < 0.001), homeostasis model assessment index (-1.3 units, p = 0.005, and -1.0 units, p = 0.014), MetS z-score (-1.9 and -2.5 units, p < 0.001) and QoL (+10 points, p = 0.029, and +11 points, p = 0.002), while the CON did not experience changes in these variables. We conclude that HIIT-LT is a viable alternative to HIIT-HR for patients who are not able/willing to undergo maximal exercise testing.

The Time Course of Cardiorespiratory Adaptations to Rowing Indoor Training in Post-Menopausal Women

BACKGROUND

Post-menopausal women have impaired cardiorespiratory responses to exercise compared to young women. Exercise training may counterbalance impairments, but the time-dependent effects of exercise training remain unclear. The current study aims to investigate the effects of rowing training on maximal aerobic capacity and time-course cardiorespiratory adaptations in older women.

METHODS

Female participants (n = 23) were randomly allocated to the experimental group (EXP; n = 23; 66 ± 5 years old) enrolled in rowing exercise training and control group (CON; n = 10; 64 ± 4 years old). The cardiopulmonary exercise test (CET) was performed in a cycle ergometer pre- and post-interventions. Oxygen uptake (VO2), stroke volume (SV), cardiac output (CO), and HR were recorded during CET and analyzed at the peak of the exercise. HR was monitored during exercise recovery, and the index of HRR was calculated by ΔHRR (HRpeak-HR one-minute recovery). Every two weeks, Rowing Stepwise Exercise (RSE) in a rowing machine was performed to track specific adaptations to the exercise modality. HR was continuously recorded during RSE and corrected for the average power of each step (HR/watts). The rowing training protocol consisted of three weekly sessions of 30 min at an intensity corresponding to 60-80% of peak HR for ten weeks.

RESULTS

Rowing exercise training increased VO2, SV, and CO at the peak of the CET, and ΔHRR. Increased workload (W) and reduced HR response to a greater achieved workload (HR/W) during RSE were observed after six weeks of training.

CONCLUSIONS

Rowing exercise training is a feasible method to improve cardiorespiratory performance, vagal reactivation and heart rate adjustments to exercise in older women.

How to Test the On-Ice Aerobic Capacity of Speed Skaters? An On-Ice Incremental Skating Test for Young Skaters

Aerobic capacity is important for speed skaters to achieve good results in middle-long distance events. The technical characteristics of speed skating cause intermittent blood flow blockage in the lower limbs. Therefore, an athlete's aerobic capacity on ice may differ from that measured by cycling or running. Now, the on-ice aerobic capacity lacks methods for conducting aerobic capacity tests on ice. Objective: The objective of this study was to develop a method for measuring on-ice aerobic capacity for young athletes and to compare it with the VO2max test on cycling. Methods: This study established a test method for the on-ice aerobic capacity of young, high-level speed skaters with incremental load (on-ice incremental skating test, OIST) through expert interviews and literature review. In the first part, OIST was used to test the aerobic abilities of 65 youth professional speed skaters (51 males and 14 females) on ice and to explore the correlation with their specific performance. The second part compares the relationship between aerobic capacity on ice and aerobic capacity on bicycle of 18 young high-level male athletes. The third part establishes the regression formula of ice ventilation threshold heart rate. The OIST established in this study can evaluate the on-ice aerobic capacity of athletes from National Level and Level 1&2 in China. The athletes' on-ice aerobic capacity indicators were significantly lower than those of the cycling test. However, the values of absolute VO2max and absolute ventilatory threshold had a high correlation (R = 0.532, p < 0.05; R = 0.584, p < 0.05). The regression formula of ventilatory threshold heart rate on ice = 0.921 × HRmax (Cycling test) -9.243. The OIST established in this study meets the characteristics and requirements of the VO2max measurement method. The OIST seems to be able to better evaluate the aerobic capacity of athletes skating on ice. The indicators of maximum oxygen uptake and ventilation threshold in OIST were significantly lower than those in the aerobic cycling test, but there was a good correlation. The aerobic cycling test can be used as an important selection index of the ice aerobic capacity of speed skaters. The regression formula will provide an important basis for coaches to accurately monitor the intensity of ice training.

Estimated power output for a distance run and maximal oxygen uptake in young adults

Background: Both cardiopulmonary exercise testing (CPET) and run field tests are recommended by the American Heart Association for assessing the maximal oxygen uptake (VO₂ max) of youth. Power output was highly correlated with VO₂ max in CPET. However, it is unclear regarding the correlations of time and estimated power output (EPO) for a run field test with VO₂ max obtained from CPET in young adults. Methods: This study included 45 participants, aged 20-40 years, from a sample of 1,120 military personnel who completed a 3,000-m run field test in Taiwan in 2020. The participants subsequently received CPET using the Bruce protocol to assess VO₂ max in the same year. According to the physics rule, EPO (watts) for the run field test was defined as the product of half body mass (kg) and [distance (3000-m)/time (s) for a run field test]. Pearson product-moment correlation analyses were performed. Results: The Pearson correlation coefficient (r) of time against EPO for the run field test was estimated to be 0.708 (p <0.001). The correlation coefficient between the time for the run field test and VO₂ max (L/min) in CPET was estimated to be 0.462 (p = 0.001). In contrast, the correlation coefficient between time for the run field test and VO₂ max scaled to body mass in CPET was estimated to be 0.729 (p <0.001). The correlation coefficient of EPO for the run field test against VO₂ max in CPET was estimated to be 0.813 (p <0.001). Conclusion: In young adults, although the time for a run field test was a reliable estimate of VO₂ max scaled to body mass, EPO proportional to the mean square velocity was found as a superior estimate of VO₂ max.

Effects of molecular hydrogen supplementation on fatigue and aerobic capacity in healthy adults: A systematic review and meta-analysis

Background

Fatigue is oftentimes induced by high-intensity exercise potentially via the exceeded amount of reactive oxygen species, leading to diminished functions (e.g., aerobic capacity) and increased risk of injuries. Studies indicate that molecular hydrogen (H₂), with antioxidant and anti-inflammatory properties, may be a promising strategy to alleviate fatigue and improve aerobic capacity. However, such effects have not been comprehensively characterized.

Objective

To systematically assess the effects of in taking H₂ on fatigue and aerobic capacity in healthy adults.

Methods

The search was conducted in August 2022 in five databases. Studies with randomized controlled or crossover designs that investigated the rating of perceived exertion (RPE), maximal oxygen uptake (VO_2max), peak oxygen uptake (VO_2peak), and endurance performance were selected. The data (mean ± standard deviation and sample size) were extracted from the included studies and were converted into the standardized mean difference (SMD). Random-effects meta-analyses were performed. Subgroup analysis was used to analyze potential sources of heterogeneity due to intervention period, training status, and type of exercise.

Results

Seventeen publications (19 studies) consisting of 402 participants were included. The pooled effect sizes of H₂ on RPE (SMD_pooled = -0.38, 95%CI -0.65 to -0.11, p = 0.006, I ² = 33.6%, p = 0.149) and blood lactate (SMD_pooled = -0.42, 95% CI -0.72 to -0.12, p = 0.006, I ² = 35.6%, p = 0.114) were small yet significant with low heterogeneity. The pooled effect sizes of H₂ on VO_2max and VO_2peak (SMD_pooled = 0.09, 95% CI -0.10 to 0.29, p = 0.333, I ² = 0%, p = 0.998) and endurance performance (SMD_pooled = 0.01, 95% CI -0.23 to 0.25, p = 0.946, I ² = 0%, p > 0.999) were not significant and trivial without heterogeneity. Subgroup analysis revealed that the effects of H₂ on fatigue were impacted significantly by the training status (i.e., untrained and trained), period of H₂ implementation, and exercise types (i.e., continuous and intermittent exercises).

Conclusions

This meta-analysis provides moderate evidence that H₂ supplementation alleviates fatigue but does not enhance aerobic capacity in healthy adults.

Systematic review registration

www.crd.york.ac.uk/PROSPERO/, identifier: CRD42022351559.

The Effects of Nordic Walking with Poles with an Integrated Resistance Shock Absorber on Red Blood Cell Distribution and Cardiorespiratory Efficiency in Postmenopausal Women-A Randomized Controlled Trial

BACKGROUND

Age-related reduction in exercise capacity is manifested by a rapid development of fatigue. Research confirmed the adverse prognostic value of red blood cell distribution width (RDW-CV), an independent factor in heart failure, coronary heart disease and myocardial infarction. Physical exercise improves and helps to maintain cardiorespiratory fitness. The aim of our study was to examine the impact of 8 weeks' Nordic walking training with classic poles (NW) and NW training with poles with an integrated resistance shock absorber (NW with RSA) on RDW-CV levels and to assess correlations between RDW-CV levels and cardiorespiratory performance in postmenopausal women.

METHODS

In this study, 32 postmenopausal women (NW-16, NW with RSA-16) participated in eight weeks of walking training. The mean age of women was 66.56 ± 4.23 year. and BMI 26.99 ± 3.86 kg/m². At the beginning and at the end of the study, spirometry and exercise tests were performed. Haematological parameters were determined in the venous blood.

RESULTS

Statistical analysis of differences in post-training changes in the parameters between the groups studied showed a significant difference in change in body weight (∆body weight) (p < 0.05; ES: 0.778), BMI (∆BMI) (p < 0.05; ES: 0.778), waist circumference (∆WC) (p < 0.05; ES: 1.225) and (∆RDW-SD) (p < 0.05; ES: 1.215). There were no changes in electrocardiographic and spirometric parameters.

CONCLUSIONS

Based on the findings from the present study, it can be assumed that endurance and resistance exercise can significantly reduce disease severity and mortality. A clinical analysis of RDW levels, together with other cardiological and biochemical parameters, can provide practical prognostic information relating to cardiovascular disease, mortality risk and treatment outcomes.

The effect of high-intensity interval training on cognitive function in patients with substance use disorder: Study protocol for a two-armed randomized controlled trial

Introduction

Substance use disorder (SUD) is characterized by cognitive impairment, especially executive dysfunction. Executive function is recognized as an important determinant of treatment outcome as it is associated with dropout rate, attendance to therapy and potential relapse after treatment termination. Physical activity can have beneficial effects on cognitive function, but there is still a lack of knowledge regarding potential benefits of aerobic exercise for executive function in SUD treatment. The aim of this study is to examine the effect of aerobic high-intensity interval training (HIIT) on cognitive function and the subsequent effect on treatment outcome in patients with SUD.

Methods and analysis

This study is a randomized controlled trial, including men and women ≥18 years with diagnosed SUD by ICD-10. The patients will be recruited from the department for inpatient treatment at Blue Cross - Lade Addiction Treatment Center, Trondheim, Norway. Participants will be randomized 1:1 into either HIIT (3x/week) + treatment as usual (TAU), or TAU alone. Study outcomes will be assessed at baseline, after eight weeks of intervention, and at 3- and 12-months follow-up. The primary outcome is to compare the change in executive function (via altered BRIEF-A score, Behavior Rating Inventory of Executive Function-Adult) measured between the two study groups after eight weeks. Secondary outcomes include mapping of cognitive function in different subgroups (e.g. type of substance, age, fitness level), collecting self-reported information about quality of life, craving, sleep quality, etc., as well as assessing compliance to TAU and long-term treatment outcome.

Ethics and dissemination

The project was approved by the Regional Ethical Committee and will be performed in accordance with this protocol and the Declaration of Helsinki. Written informed consent will be obtained from all participants prior to inclusion. This project will explore a novel approach to how exercise can be applied in SUD treatment, beyond the well-known effects on physical health. We expect to achieve new knowledge in regard to what extent HIIT can improve cognitive abilities and subsequent treatment outcome in SUD.

Trial registration number

https://www.clinicaltrials.gov/NCT05324085.

Comprehensive cardiopulmonary profile of individuals with Down syndrome

BACKGROUND

Individuals with Down syndrome (DS) have low levels of cardiorespiratory fitness and previous studies have shown that these low levels of fitness have a physiological cause. During exercise, the cardiovascular, ventilatory and muscular systems are simultaneously active. While individual parameters of these systems have been investigated in DS before, the interaction between these parameters and systems have not been discussed in detail. Doing so may provide important insight regarding the aetiology of low cardiorespiratory fitness and which parameters of the cardiovascular, pulmonary and muscular systems are altered in individuals with DS compared with their peers without DS.

METHODS

Cardiopulmonary exercise tests were performed in healthy adults with and without DS. Parameters related to the cardiovascular, ventilatory and muscular systems were collected until VO_2peak . In total, 51 participants were included in analysis, of which 21 had DS.

RESULTS

Individuals with DS showed lower peak values for all collected outcomes (P ≤ 0.001) compared with those without DS, except for ventilatory threshold as a percentage of maximal oxygen uptake and V_E /VCO₂ slope, which were similar.

CONCLUSIONS

Our results show that individuals with DS present impairments across the cardiovascular, ventilatory and muscular aspects of the cardiopulmonary system.

Effect of Intermittent Hypoxic Training on Selected Biochemical Indicators, Blood Rheological Properties, and Metabolic Activity of Erythrocytes in Rowers

The study assessed the effect of 3-week intermittent hypoxic training on blood biochemical indicators (blood morphology, fibrinogen), blood rheological properties (erythrocyte deformability, aggregation), erythrocyte enzymatic activity (acetylcholinesterase), and maximal oxygen uptake in competitive rowers. Fourteen male rowers were divided into two equal groups: experimental, training on ergometers under normobaric hypoxia (FiO₂ = 16.0%), and control, training on ergometers under normoxia (FiO₂ = 21%). Fasting blood was taken before and after training. A significant between-group difference in neutrophil levels before training was noted and a significant decrease in white blood cells in the hypoxia group. Both groups exhibited an increase in elongation index. In the normoxia group, a significant increase in erythrocyte aggregation amplitude was revealed. No significant changes occurred in the other biochemical indicators or those evaluating erythrocyte metabolic activity. Normobaric hypoxia increased erythrocyte deformability, improving blood rheological properties. Maximal oxygen uptake significantly increased only in the experimental group.

Impact of Mechanical Circulatory Support on Exercise Capacity in Patients With Advanced Heart Failure

Approximately 6 million individuals have heart failure in the United States alone and 15 million in Europe. Left ventricular assist devices (LVAD) improve survival in these patients, but functional capacity may not fully improve. This article examines the hypothesis that patients supported by LVAD experience persistent reductions in functional capacity and explores mechanisms accounting for abnormalities in exercise tolerance.

Correlation between Cardiopulmonary Indices and Running Performance in a 14.5 km Endurance Running Event

BACKGROUND

Running is a common recreational activity, and the number of long-distance-race participants is continuously growing. It is well-established that regular physical activity can prevent and manage non-communicable diseases and benefit public health. Training for a long-distance race requires development of specific aerobic abilities and should generate the desired race performance. The purpose of this study was to support the training design and motivation of recreational endurance runners, by investigating whether a 14.5 km race performance of long-distance runners correlates with their cardiopulmonary indices measured in the laboratory.

METHODS

To examine the relationships of a 14.5 km running performance with the cardiopulmonary parameters of amateur runners, a cross-sectional study design was applied. Fifteen (eleven men and four women) recreational long-distance runners (aged 41.3 ± 9.2 years) from Northern Greece were included in the study and were evaluated in the laboratory within one week before an endurance running race-the 14.5 km Philip Road race, in Greece. The laboratory-based examinations of the athletes consisted of a comprehensive medical pre-participation screening and maximal cardiopulmonary exercise testing.

RESULTS

The results showed that the 14.5 km race performance time (73.8 ± 9.7 min) significantly correlated with the cardiopulmonary-exercise-testing speed-related indices at specific submaximal and maximal workloads (p < 0.01, p < 0.05), while the cardiopulmonary indices of oxygen uptake did not reliably predict race running time (p > 0.05).

CONCLUSIONS

There is a better correlation of the 14.5 km running performance of recreational long-distance runners with the cardiopulmonary-exercise-testing speed-related indices at specific workloads than with the indices of oxygen uptake, running economy or respiratory economy. When preparing a training strategy, amateur long-distance runners should mostly rely on specific running-speed-related laboratory data rather than on oxygen-uptake values.

Performance and Submaximal Adaptations to Additional Speed-Endurance Training Vs. Continuous Moderate-Intensity Aerobic Training in Male Endurance Athletes

We examined performance and submaximal adaptations to additional treadmill-based speed-endurance training (SET) vs. continuous moderate-intensity aerobic training (MIT) twice / week. Twenty-two male endurance athletes were tested before and after 10-week SET (6-12 × 30-s sprints separated by 3-min rest intervals) and MIT (2040 min continuous running at ~70% maximal oxygen uptake [V̇O_2max]). The SET group attained greater acute heart rate (HR) and blood lactate responses than the MIT group (d = 0.86–0.91). The SET group improved performance in a time-to-exhaustion trial, V̇O_2max, and lactate threshold (d = 0.50–0.73), whereas no training-induced changes were observed in the MIT group. Additionally, the SET group reduced oxygen uptake, mean HR and improved running economy (d = 0.53–0.86) during running at 10 and 12 km·h^-1. Additional SET imposes greater physiological demands than MIT resulting in superior performance adaptations and reduced energy cost in endurance athletes.

Validity and Reliability of New Equations for the Prediction of Maximal Oxygen Uptake in Male and Female Elite Adolescent Rowers

The aim of this study was to develop accurate, reliable, and reproductive equations for the prediction of maximum oxygen uptake (V˙O_2max) in male and female high-level adolescent rowers. This study included two parts. In the first part, V̇O_2max was evaluated in 106 male and 83 female high-level adolescent rowers during an incremental step test (IRT) on a rowing ergometer, and stepwise multiple regression analyses were used for the development of new equations. In the second part, these equations were tested in 26 new high-level adolescent rowers of the same age and anthropometrical characteristics (boys: 15.27 ± 2.70 yrs and 15.34 ± 2.80 yrs; 72.37 ± 10.96 kg and 70.96 ± 10.65 kg; girls: 15.00 ± 2.11 yrs and 15.94 ± 2.71 yrs; 62.50 ± 7.14 kg and 63.41 ± 6.72 kg for parts 1 and 2, respectively; p > 0.05). V̇O_2max was predicted from the combination of lean body mass (LBM) and the distance covered during the last 4 min stage of the IRT (boys: r² = 0.715, F = 68.74, p = 0.001; girls: r² = 0.769, F = 57.81, p = 0.001). In the second part, no significant differences were identified when the new equations were tested against measured V̇O_2max (boys: 3971.15 ± 713.38 mL·min⁻¹ vs. 3915.83 ± 704.43 mL·min⁻¹; girls: 3272.75 ± 551.46 mL·min⁻¹ vs. 3308.94 ± 557.59 mL·min⁻¹ for measured and predicted values, respectively; p > 0.05). In conclusion, V̇O_2max of high-level adolescent rowers can be predicted with high accuracy, reliability, and repeatability using simple and easily evaluated anthropometric and performance variables.

Sex Differences in Physiological Determinants of Performance in Elite Adolescent, Junior, and Senior Cross-Country Skiers

PURPOSE

To compare sex differences in physiological determinants of skiing performance in elite adolescent, junior, and senior cross-country skiers matched for within-age-group performance level.

METHODS

Eight male and 12 female adolescent (15 [1] y), 8 male and 7 female junior (18 [1] y), and 7 male and 6 female senior (28 [5] y) skiers participated. Gross efficiency was calculated during submaximal uphill treadmill roller skiing (approximately 84% of peak oxygen uptake [V˙O2peak]) using the G2 ski-skating technique. Distance covered, V˙O2peak, and maximal accumulated oxygen deficit were established from a 3-minute time-trial. Fifteen-second maximal skiing power was calculated from an incremental treadmill speed test. Finally, upper- and lower-body maximal strength tests were conducted.

RESULTS

The 3-minute time-trial distance and maximal skiing power were, respectively, 23% and 15% (adolescent), 24% and 19% (junior), and 17% and 14% (senior) greater for men than women (all groups, P ≤ .01, effect size [ES] = 2.43-4.18; very large). V˙O2peak relative to body mass was 17% (adolescent, P = .002, ES = 1.66, large), 21% (junior, P < .01, ES = 2.60, very large), and 19% (senior, P < .01, ES = 2.35, very large) greater for men than women. The within-age-group sex differences in gross efficiency, relative accumulated oxygen deficit, and strength were not significant, with the exception of greater lower-body strength in male than female juniors (P = .01, ES = 1.26, large).

CONCLUSION

The within-age-group sex difference in skiing performance is of similar magnitude for adolescent, junior, and senior skiers. This difference can likely be attributed to the large to very large sex difference in V˙O2peak within all age-groups.

Maximal Oxygen Uptake, VO(2) Max, Testing Effect on Blood Glucose Level in Adolescents with Type 1 Diabetes Mellitus

Assessing maximal oxygen uptake (VO2 max) is generally considered safe when performed properly for most adolescents; however, for adolescents with type 1 diabetes mellitus (T1DM), monitoring glucose levels before and after exercise is critical to maintaining euglycemic ranges. Limited guidance exists for glucose level recommendations for the pediatric population; therefore, the purpose of this retrospective clinical chart review study was to determine the effects of VO2 max testing on blood glucose levels for adolescents with T1DM. A total of 22 adolescents (mean age = 15.6 ± 1.8 years; male = 13, 59.1%) with a diagnosis of T1DM participated in a Bruce protocol for VO2 max from January 2019 through February 2020. A statistically significant reduction in glucose levels between pretest (<30 min, mean = 191.1 mg/dL ± 61.2) and post-test VO2 max (<5 min, mean = 166.7 mg/dL ± 57.9); t(21) = 2.3, p < 0.05) was detected. The results from this current study can help guide health and fitness professionals in formulating glycemic management strategies in preparatory activities prior to exercise testing and during exercise testing.

Predictors of Academic Performance in High School Students: The Longitudinal ASAP Study

Academic performance is influenced by multitude factors. However, little is known about their relative importance and how they evolve over time. The purpose of the present study was to determine the relative importance of cognitive control, physical, psychological and sociological factors as well as lifestyle habits in predicting academic performance in high school students using cross sectional and longitudinal approaches. One hundred and eighty-five grade seventh to ninth students (mean age: 13.1 ± 1.0 years old) from a single high school completed a 3-year prospective study. Academic performance, cognitive control, physical, psychological and sociological factors as well as lifestyle habits were assessed every year during the 3-year study. Results showed that different combinations of factors were found to predict academic performance measures in both male and female students at baseline and after a 3-year period. For example, in female students, screen time and VO₂ max were found to be important predictors of academic performance, whereas working memory was the only recurring factor in predicting academic performance in male students. Moreover, our models were able to explain between 6.1 to 52.2% of the variation in the change of the different measures of academic performance. Results of the present study show that academic performance may be predicted by a wide range of multiple factors in high school students. Indeed, the factors that predicted academic performance varied between school subjects, sex and study design, highlighting the complexity of predicting academic performance in high school students.

Effects of Interval Training Under Hypoxia on the Autonomic Nervous System and Arterial and Hemorheological Function in Healthy Women

Purpose

The present study verified the effects of interval training under hypoxia, a novel exercise modality for health promotion, on the autonomic nervous system (ANS) and arterial and hemorheological function in healthy women.

Methods

Twenty healthy Korean women (age: 19–29 [24.85 ± 3.84] years) were equally assigned to interval normoxic training (INT, n = 10; residing and training under normoxia) and interval hypoxic training (IHT, n = 10; residing under normoxia and training under 526 mmHg hypobaric hypoxia) groups. All participants performed 90-min of training sessions composed of 15-min of warm-up, 60-min of interval training, and 15-min of cool-down. The interval training sessions composed of 10 repetitions of interval exercise using a treadmill (5 min of exercise corresponding to 90–95% maximal heart rate [HR] and 1 min of rest). The training was performed 3 days per week for 6 weeks. All participants underwent body composition, HR variability, brachial-ankle pulse wave velocity, flow-mediated dilation (FMD), red blood cell (RBC) deformability and aggregation, and maximal oxygen uptake (VO₂max) measurements before and after training.

Results

There were no significant differences in body composition between the groups. The IHT group showed a significant improvement in the ANS function (root mean square of successive differences, high frequency, and low frequency/high frequency ratio), arterial stiffness, arterial endothelial function (FMD), hemorheological function (RBC deformability and aggregation), and aerobic performance (VO₂max) compared with the INT (all p < 0.05).

Conclusion

In comparison with the interval training under normoxia, the interval training under hypoxia is a novel and effective exercise modality for promoting aerobic performance with the ANS and arterial and hemorheological function in healthy women.

Comparison of the Gauntlet Test With Standard Laboratory Measures of Aerobic Fitness

ABSTRACT

Burnsed-Torres, ML, Wichmann, TK, Clayton, ZS, and Hahn, ME. Comparison of the Gauntlet test with standard laboratory measures of aerobic fitness. J Strength Cond Res 36(2): 386-391, 2022-The purpose of this study was to validate whether the Gauntlet test (GT) can accurately estimate individual aerobic endurance performance compared with standard laboratory-based physiological tests. The GT required athletes to complete 5 maximal effort running stages, with a 1-minute break between each stage, with the goal of achieving the best overall time. Eighteen men (n = 9) and women (n = 9) (age, 23.5 ± 4.13 years; body mass index, 23.1 ± 7.62 kg·m-2; 5k time, 22 ± 7 minutes; 10k time, 47 ± 15 minutes; V̇o2max, 52.3 ± 8 ml·kg-1·min-1) completed a lactate threshold test and V̇o2max test (laboratory measures). Four to 14 days later, subjects completed the GT on an outdoor track. Blood lactate (bLa), V̇o2max, and heart rate (HR) were recorded during the laboratory session. Blood lactate, HR, stage completion time, and overall completion time were recorded during the GT. Linear regression correlation analyses revealed a significant inverse association between V̇o2max (mL·kg-1·min-1) and GT completion time (r = -0.88, P < 0.0001). In addition, there were significant correlations between V̇o2max maximum HR and GT maximum HR (r = 0.89, P < 0.0001) and V̇o2max 3-minute post bLa and GT 3-minute post bLa (r = 0.63, P = 0.0029). Sex-specific analysis showed significant inverse associations between female and male GT completion time and V̇o2max (r = -0.70, P = 0.0352; r = -0.94, P < 0.0002). Bland-Altman plots were used to evaluate concordance between GT completion time, V̇o2max, maximum HR, and 3-minute post bLa. Results suggest the GT is a valid assessment to accurately estimate aerobic endurance performance similar to standard laboratory methods.

The Determination of Step Frequency in 3-min Incremental Step-in-Place Tests for Predicting Maximal Oxygen Uptake from Heart Rate Response in Taiwanese Adults

The maximal oxygen uptake (VO_2max) prediction models established by step tests are often used for evaluating cardiorespiratory fitness (CRF). However, it is unclear which type of stepping frequency sequence is more suitable for the public to assess the CRF. Therefore, the main purpose of this study was to test the effectiveness of two 3-min incremental step-in-place (3MISP) tests (i.e., 3MISP_30s and 3MISP_60s) with the same total number of steps but different step-frequency sequences in predicting VO_2max. In this cross-sectional study, a total of 200 healthy adults in Taiwan completed 3MISP_30s and 3MISP_60s tests, as well as cardiopulmonary exercise testing. The 3MISP_30s and 3MISP_60s models were established through multiple stepwise regression analysis by gender, age, percent body fat, and 3MISP-heart rate. The statistical analysis included Pearson's correlations, the standard errors of estimate, the predicted residual error sum of squares, and the Bland-Altman plot to compare the measured VO_2max values and those estimated. The results of the study showed that the exercise intensity of the 3MISP_30s test was higher than that of the 3MISP_60s test (% heart rate reserve (HRR) during 3MISP_30s vs. %HRR during 3MISP_60s = 81.00% vs. 76.81%, p < 0.001). Both the 3MISP_30s model and the 3MISP_60s model explained 64.4% of VO_2max, and the standard errors of the estimates were 4.2043 and 4.2090 mL·kg^-1·min^-1, respectively. The cross-validation results also indicated that the measured VO_2max values and those predicted by the 3MISP_30s and 3MISP_60s models were highly correlated (3MISP_30s model: r = 0.804, 3MISP_60s model: r = 0.807, both p < 0.001). There was no significant difference between the measured VO_2max values and those predicted by the 3MISP_30s and 3MISP_60s models in the testing group (p > 0.05). The results of the study showed that when the 3MISP_60s test was used, the exercise intensity was significantly reduced, but the predictive effectiveness of VO_2max did not change. We concluded that the 3MISP_60s test was physiologically less stressful than the 3MISP_30s test, and it could be a better choice for CRF evaluation.

Smartphone-Assisted High-Intensity Interval Training in Inflammatory Rheumatic Disease Patients: Randomized Controlled Trial

BACKGROUND

Patients with inflammatory rheumatic diseases (IRDs) experience disease-related barriers to physical training. Compared with the general population, IRD patients are reported to have reduced maximal oxygen uptake (VO2max) and physical activity levels. Supervised high-intensity interval training (HIIT) is documented to counteract the reduced VO2max and poor cardiovascular health associated with IRDs. However, supervised HIIT is resource demanding.

OBJECTIVE

This study sought to investigate if self-administered 4×4-min HIIT guided by a smartphone app (Myworkout GO) could yield similar HIIT-induced effects as standard 4×4-min HIIT performed under the guidance and supervision of health care professionals. The effects studied were on VO2max and health-related quality of life (HRQoL).

METHODS

Forty patients (33 female patients, mean age 48 years, SD 12 years; 7 male patients, mean age 52 years, SD 11 years) diagnosed with rheumatoid arthritis, spondyloarthritis, or systemic lupus erythematosus were randomized to a supervised group (SG) or an app group (AG). Both groups were instructed to perform 4×4-min intervals with a rate of perceived exertion of 16 to 17, corresponding to 85% to 95% of the maximal heart rate, twice a week for 10 weeks. Treadmill VO2max and HRQoL measured using RAND-36 were assessed before and after the exercise period.

RESULTS

VO2max increased (P<.001) in both groups after 10 weeks of HIIT, with improvements of 3.6 (SD 1.3) mL/kg/min in the SG and 3.7 (SD 1.5) mL/kg/min in the AG. This was accompanied by increases in oxygen pulse in both groups (P<.001), with no between-group differences apparent for either measure. Improvements in the HRQoL dimensions of bodily pain, vitality, and social functioning were observed for both groups (P<.001 to P=.04). Again, no between-group differences were detected.

CONCLUSIONS

High-intensity 4×4-min interval training increased VO2max and HRQoL, contributing to patients' reduced cardiovascular disease risk, improved health and performance, and enhanced quality of life. Similar improvements were observed following HIIT when IRD patients were guided using perceived exertion by health care professionals or the training was self-administered and guided by the app Myworkout GO. Utilization of the app may help reduce the cost of HIIT as a treatment strategy in this patient population.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04649528; https://clinicaltrials.gov/ct2/show/NCT04649528.

Effects of a Low-Carbohydrate High-Fat Diet Combined with High-Intensity Interval Training on Body Composition and Maximal Oxygen Uptake: A Systematic Review and Meta-Analysis

The low-carbohydrate high-fat (LCHF) diet has recently been subject to attention on account of its reported influences on body composition and physical performance. However, the combined effect of LCHF with high-intensity interval training (HIIT) is unclear. A systematic review and meta-analysis were conducted to explore the effect of the LCHF diet combined with HIIT on human body composition (i.e., body weight (BM), body mass index (BMI), fat mass (FM), body fat percentage (BFP), fat-free mass (FFM)) and maximal oxygen uptake (VO_2max). Online libraries (PubMed, Web of Science, EMBASE, Cochrane Library, EBSCO, CNKI, Wan Fang) were used to search initial studies until July 2021, from which 10 out of 2440 studies were included. WMD served as the effect size with a confidence interval value of 95%. The results of meta-analysis showed a significant reduction in BM (WMD = −5.299; 95% CI: −7.223, −3.376, p = 0.000), BMI (WMD = −1.150; 95% CI: −2.225, −0.075, p = 0.036), BFP (WMD = −2.787; 95% CI: −4.738, −0.835, p = 0.005) and a significant increase in VO_2max (WMD = 3.311; 95% CI: 1.705, 4.918, p = 0.000), while FM (WMD = −2.221; 95% CI: −4.582, 0.139, p = 0.065) and FFM (WMD = 0.487; 95% CI: −3.512, 4.469, p = 0.814) remained unchanged. In conclusion, the LCHF diet combined with HIIT can reduce weight and fat effectively. This combination is sufficient to prevent muscle mass loss during LCHF, and further enhance VO_2max. Further research might be required to clarify the effect of other types of exercise on body composition and physical performance during LCHF.

Development and Validation of 3 Min Incremental Step-In-Place Test for Predicting Maximal Oxygen Uptake in Home Settings: A Submaximal Exercise Study to Assess Cardiorespiratory Fitness

The purpose of this research was to develop the 3 min incremental step-in-place (3MISP) test for predicting maximal oxygen uptake (V.O_2max). A total of 205 adults (20–64 years) completed the 3MISP and V.O_2max tests. Using age, gender, body composition (BC) including percent body fat (PBF) or body mass index (BMI), and with or without heart rate (HR) at the beginning of exercise (HR0) or difference between HR at the third minute during the exercise and the first minute post exercise (ΔHR3 − HR4) in the 3MISP test, six V.O_2max prediction models were derived from multiple linear regression. Age (r = −0.239), gender (r = 0.430), BMI (r = −0.191), PBF (r = −0.706), HR0 (r = −0.516), and ΔHR3 − HR4 (r = 0.563) were significantly correlated to V.O_2max. Among the six V.O_2max prediction models, the PBF model^{∆HR3 − HR4} has the highest accuracy. The simplest models with age, gender, and PBF/BMI explained 54.5% of the V.O_2max in the PBF model^BC and 39.8% of that in the BMI model^BC. The addition of HR0 and ∆HR3 − HR4 increases the variance of V.O_2max explained by the PBF and BMI models^{∆HR3 − HR4} by 17.98% and 45.23%, respectively, while standard errors of estimate decrease by 10.73% and 15.61%. These data demonstrate that the models established using 3MISP-HR data can enhance the accuracy of V.O_2max prediction.

High-Intensity Interval Training for Heart Failure Patients With Preserved Ejection Fraction (HIT-HF)-Rational and Design of a Prospective, Randomized, Controlled Trial

Background: The pathophysiology of HF with preserved ejection fraction (HFpEF) has not yet been fully understood and HFpEF is often misdiagnosed. Remodeling and fibrosis stimulated by inflammation appear to be main factors for the progression of HFpEF. In contrast to patients with HF with reduced ejection fraction, medical treatment in HFpEF is limited to relieving HF symptoms. Since mortality in HFpEF patients remains unacceptably high with a 5-year survival rate of only 30%, new treatment strategies are urgently needed. Exercise seems to be a valid option. However, the optimal training regime still has to be elucidated. Therefore, the aim of the study is to investigate the effects of a high-intensity interval (HIT) training vs. a moderate continuous training (MCT) on exercise capacity and disease-specific mechanisms in a cohort of patients with HFpEF. Methods: The proposed study will be a prospective, randomized controlled trial in a primary care setting including 86 patients with stable HFpEF. Patients will undergo measurements of exercise capacity, disease-specific blood biomarkers, cardiac and arterial vessel structure and function, total hemoglobin mass, metabolic requirements, habitual physical activity, and quality of life (QoL) at baseline and follow-up. After the baseline visit, patients will be randomized to the intervention or control group. The intervention group (n = 43) will attend a supervised 12-week HIT on a bicycle ergometer combined with strength training. The control group (n = 43) will receive an isocaloric supervised MCT combined with strength training. After 12 weeks, study measurements will be repeated in all patients to quantify the effects of the intervention. In addition, telephone interviews will be performed at 6 months, 1, 2, and 3 years after the last visit to assess clinical outcomes and QoL. Discussion: We anticipate clinically significant changes in exercise capacity, expressed as VO_2peak, as well as in disease-specific mechanisms following HIT compared to MCT. Moreover, the study is expected to add important knowledge on the pathophysiology of HFpEF and the clinical benefits of a training intervention as a novel treatment strategy in HFpEF patients, which may help to improve both QoL and functional status in affected patients. Trial registration: ClinicalTrials.gov, identifier: NCT03184311, Registered 9 June 2017.

Effects of Increased Load of Low- Versus High-Intensity Endurance Training on Performance and Physiological Adaptations in Endurance Athletes

PURPOSE

To compare the effects of increased load of low- versus high-intensity endurance training on performance and physiological adaptations in well-trained endurance athletes.

METHODS

Following an 8-week preintervention period, 51 (36 men and 15 women) junior cross-country skiers and biathletes were randomly allocated into a low-intensity (LIG, n = 26) or high-intensity training group (HIG, n = 25) for an 8-week intervention period, load balanced using the overall training impulse score. Both groups performed an uphill running time trial and were assessed for laboratory performance and physiological profiling in treadmill running and roller-ski skating preintervention and postintervention.

RESULTS

Preintervention to postintervention changes in running time trial did not differ between groups (P = .44), with significant improvements in HIG (-2.3% [3.2%], P = .01) but not in LIG (-1.5% [2.9%], P = .20). There were no differences between groups in peak speed changes when incremental running and roller-ski skating to exhaustion (P = .30 and P = .20, respectively), with both modes being significantly improved in HIG (2.2% [3.1%] and 2.5% [3.4%], both P < .01) and in roller-ski skating for LIG (1.5% [2.4%], P < .01). There was a between-group difference in running maximal oxygen uptake changes (P = .04), tending to improve in HIG (3.0% [6.4%], P = .09) but not in LIG (-0.7% [4.6%], P = .25). Changes in roller-ski skating peak oxygen uptake differed between groups (P = .02), with significant improvements in HIG (3.6% [5.4%], P = .01) but not in LIG (-0.1% [0.17%], P = .62).

CONCLUSION

There was no significant difference in performance adaptations between increased load of low- versus high-intensity training in well-trained endurance athletes, although both methods improved performance. However, increased load of high-intensity training elicited better maximal oxygen uptake adaptations compared to increased load of low-intensity training.

Stroke and cardiorespiratory fitness

Összefoglaló. A fizikai inaktivitás a cardiovascularis betegségek - így a stroke - jelentős kockázati tényezője. A rendszeres testmozgás növeli az aerob kapacitást, a cardiorespiratoricus fittséget - ezzel csökkenti a cardiovascularis betegségek, köztük a stroke kockázatát. Az elmúlt évek azon vizsgálataiból idéz a közlemény, amelyek a fizikai aktivitás, a cardiorespiratoricus teljesítőképesség szerepét ismertetik a stroke elsődleges és másodlagos prevenciójában. Említésre kerülnek az aerob kapacitás mérésének módszerei. A nemzetközi tapasztalatok azt igazolják, hogy magas cardiorespiratoricus fittség esetén közel harmadával csökken a stroke előfordulása. A WHO ajánlása mindenkinek a heti legalább 150 percnyi mérsékelten-közepesen meglihegtető testi tevékenység - ez a leggyakoribb krónikus betegségek ellen bizonyos védelmet ad. Orv Hetil. 2021; 162(39): 1567-1572. Summary. Physical inactivity is a significant risk for cardiovascular diseases, even for stroke. Regular physical activity improves aerobic capacity, cardiorespiratory fitness, aerob endurance performance (synonyms), diminishing the risk of cardiovascular diseases as well as the risk of stroke. We refer to previous literature data from the past two decades demonstrating the beneficial role of the higher aerob fitness in the primary and secondary prevention of stroke. Relevant methods of measuring aerob performance have been described previously. In the case of optimal aerobic fitness, the occurrence of stroke is lower by a third according to international experience. WHO advices moderate-medium intensity physical activity of minimum 150 minutes per week, which carries significant protection against the majority of chronic cardio-metabolic diseases. Orv Hetil. 2021; 162(39): 1567-1572.

Comparison of Physiological Responses and Muscle Activity During Incremental and Decremental Cycling Exercise

OBJECTIVE

To investigate whether a cycling test based on decremental loads (DEC) could elicit higher maximal oxygen uptake (V˙O2max) values compared with an incremental test (INC).

DESIGN

Nineteen well-trained individuals performed an INC and a DEC test on a single day, in randomized order.

METHODS

During INC, the load was increased by 20 W·min-1 until task failure. During DEC, the load started at 20 W higher than the peak load achieved during INC (familiarization trial) and was progressively decreased. Gas exchange and electromyography (EMG) activity (n = 11) from 4 lower-limb muscles were monitored throughout the tests. Physiological and EMG data measured at V˙O2max were compared between the 2 protocols using paired t tests.

RESULTS

V˙O2max during the DEC was 3.0% (5.9%) higher than during INC (range 94%-116%; P = .01), in spite of a lower power output (-21 [20] W, P < .001) at V˙O2max. Pulmonary ventilation (P = .036) and breathing rate (P = .023) were also higher during DEC. EMG activity measured at V˙O2max was not different between tests, despite the lower output during DEC.

CONCLUSIONS

A DEC exercise test produces higher V˙O2max in cycling compared with an INC test, which was accompanied by higher pulmonary ventilation and similar EMG activity. The additional O2 uptake during DEC might be related to extra work performed either by the respiratory muscles and/or the less oxidatively efficient leg muscles.

Comparison of Aerobic Capacity Changes as a Result of a Polarized or Block Training Program among Trained Mountain Bike Cyclists

This study compared the effectiveness of a block training program and a polarized training program in developing aerobic capacity in twenty trained mountain bike cyclists. The cyclists were divided into two groups: the block training program group (BT) and the polarized training program group (PT). The experiment lasted 8 weeks. During the experiment, the BT group alternated between 17-day blocks consisting of dominant low-intensity training (LIT) and 11-day blocks consisting of sprint interval training (SIT), and high-intensity interval training (HIIT), while the PT group performed SIT, HIIT, and LIT simultaneously. Before and after the experiment, the cyclists performed incremental tests during which maximal oxygen uptake (VO₂max), maximal aerobic power (Pmax), power achieved at the first ventilatory threshold (P_VT1), and at the second ventilatory threshold (P_VT2) were measured. VO₂max increased in BT group (from 3.75 ± 0.67 to 4.00 ± 0.75 L∙min^-1) and PT group (from 3.66 ± 0.73 to 4.20 ± 0.89 L∙min^-1). In addition, Pmax, P_VT1, and P_VT2 increased in both groups to a similar extent. In conclusion, the polarized training program was more effective in developing the VO₂max compared to the block program. In terms of developing other parameters characterizing the cyclists' aerobic capacity, the block and polarized program induced similar results.

Moderate-to-Vigorous Physical Activity Is Associated With Cardiorespiratory Fitness Among Primary Schoolchildren Living in Côte d'Ivoire, South Africa, and Tanzania

Background: Physical inactivity and low cardiorespiratory fitness (CRF) are independent cardiovascular risk factors among children, but have rarely been investigated concurrently in sub-Saharan Africa. The purpose of this study was to compare physical activity (PA) and CRF of primary schoolchildren living in Côte d'Ivoire (CI), South Africa (ZA), and Tanzania (TZ), to test sex- and age-related differences, and to examine whether PA and CRF are associated with each other. Methods: Baseline data from an ongoing cluster-randomized controlled trial were used, including 499 children from CI (Taabo, 49% girls, M = 8.0 ± 1.6 years), 1,074 children from ZA (Gqeberha, 49% girls, M = 8.3 ± 1.4 years), and 593 children from TZ (Ifakara, 51% girls, M = 9.4 ± 1.7 years). PA was assessed by accelerometry and CRF by a 20 m shuttle-run test. The data were analyzed using multi-/univariate analyses of variance and mixed linear models. Results: Most children met recommendations put forward by the World Health Organization for moderate-to-vigorous PA (MVPA) and achieved high CRF scores. In CI, 89.6% of the children met MVPA recommendations (boys: 91.7%, girls: 87.4%), whereas this rate was 76.9% in ZA (boys: 91.0%, girls: 62.4%), and 93.8% in TZ (boys: 95.5%, girls: 92.0%). Children from TZ had the highest CRF and MVPA levels, followed by children from CI and ZA. Boys had higher MVPA levels than girls, whereas girls engaged in more sedentary behavior. Sex differences were strongest in ZA. Sedentary behavior and MVPA were higher among older schoolchildren compared to their younger peers. Higher MVPA, but not sedentary behavior, was associated with better CRF. Conclusions: In all three settings, higher levels of MVPA were associated with higher CRF scores. Nevertheless, children living in the most urbanized setting (such as observed in ZA) were physically less active and had lower CRF than peers living in more rural areas (such as observed in CI and TZ). Particularly for girls, urbanization might increase the risk for insufficient MVPA, which may have negative effects on their CRF, thus negatively influencing health and well-being at later age.

The Impulse of Force as an Effective Indicator of Exercise Capacity in Competitive Rowers and Canoeists

The aim of the research was to present the importance of measuring the impulse of force in assessing exercise capacity in professional rowers and canoeists rather than conducting traditional physiological and biochemical analyses. A group of 20 athletes (12 rowers and 8 canoeists) underwent progressive intensity exercise tests in two testing sessions (before and after a training period). During the tests, maximal aerobic capacity, impulse of strength, metabolic indices, and markers of skeletal muscle damage were assessed. Total testosterone, free testosterone, cortisol, interleukin 1,6, and creatine kinase were evaluated in venous blood. The impulse of force at the ventilatory threshold and at the maximum load was correlated with free testosterone and a total testosterone/cortisol ratio during exercise (p ≤ 0.05) and was negatively correlated with cortisol concentration (p ≤ 0.05) in the first testing session (before training intervention). Values were positively correlated with concentration of total testosterone, free testosterone and total testosterone/cortisol, and free testosterone/cortisol ratios during exercise (p ≤ 0.05) in the second testing session (after training intervention). Biochemical indices of overtraining were correlated with maximum oxygen uptake in each session and with the impulse of force at the ventilatory threshold and the maximum load of exercise. Thus, there is an indirect relationship between maximal aerobic capacity and the impulse of force. The measurement of the impulse of force can become a simple and effective method for evaluating the overall exercise capacity of rowers because of its relationship with indices of the load and changes in hormonal indices of anabolic and catabolic processes during exercise. Therefore, it may constitute a replacement for the traditional laboratory measurement of VO_2max in highly qualified rowers and canoeists.

Estimated Artificial Neural Network Modeling of Maximal Oxygen Uptake Based on Multistage 10-m Shuttle Run Test in Healthy Adults

We aimed to develop an artificial neural network (ANN) model to estimate the maximal oxygen uptake (VO₂max) based on a multistage 10 m shuttle run test (SRT) in healthy adults. For ANN-based VO₂max estimation, 118 healthy Korean adults (59 men and 59 women) in their twenties and fifties (38.3 ± 11.8 years, men aged 37.8 ± 12.1 years, and women aged 38.8 ± 11.6 years) participated in this study; data included age, sex, blood pressure (systolic blood pressure (SBP), diastolic blood pressure (DBP)), waist circumference, hip circumference, waist-to-hip ratio (WHR), body composition (weight, height, body mass index (BMI), percent skeletal muscle, and percent body), 10 m SRT parameters (number of round trips and final speed), and VO₂max by graded exercise test (GXT) using a treadmill. The best estimation results (R² = 0.8206, adjusted R² = 0.7010, root mean square error; RMSE = 3.1301) were obtained in case 3 (using age, sex, height, weight, BMI, waist circumference, hip circumference, WHR, SBP, DBP, number of round trips in 10 m SRT, and final speed in 10 m SRT), while the worst results (R² = 0.7765, adjusted R² = 0.7206, RMSE = 3.494) were obtained for case 1 (using age, sex, height, weight, BMI, number of round trips in 10 m SRT, and final speed in 10 m SRT). The estimation results of case 2 (using age, sex, height, weight, BMI, waist circumference, hip circumference, WHR, number of round trips in 10 m SRT, and final speed in 10 m SRT) were lower (R² = 0.7909, adjusted R² = 0.7072, RMSE = 3.3798) than those of case 3 and higher than those of case 1. However, all cases showed high performance (R²) in the estimation results. This brief report developed an ANN-based estimation model to predict the VO₂max of healthy adults, and the model’s performance was confirmed to be excellent.