Caffeine and sport

Caffeine is a trimethylxanthine found in coffee and several other foods and beverages. Its stimulatory effects make it an interesting strategy to boost performance for athletic populations. Scientific evidence supports its efficacy to improve high-intensity endurance exercise, explosive and high-intensity efforts, resistance exercise, team sports and combat sports, though individual variation in the ergogenic response to caffeine exists. Supplementation can be taken in many forms including dissolved in water, via capsules, coffee, energy drinks and caffeinated gum; ingestion via capsules, dissolved in water or in caffeinated gum appear to be most effective. Variability in the exercise response following caffeine supplementation may be explained by genetic factors or habitual caffeine consumption. Caffeine is an excellent supplement for athletes looking to improve their exercise performance, though some consideration of side-effects and impact on sleep are warranted.

Carbohydrate mouth rinse is no more effective than placebo on running endurance of dehydrated and heat acclimated athletes

PURPOSE

To determine whether carbohydrate mouth rinsing would improve endurance running performance of tropical natives in a warm-humid (30 °C and 70% relative humidity) environment.

METHOD

Twelve endurance male runners [age 25 ± 3 years; peak aerobic capacity ([Formula: see text]O_2peak) 57.6 ± 3.6 mL^.kg^-1.min^-1] completed three time-to-exhaustion (TTE) trials at ~ 70% [Formula: see text]O_2peak while swilling 25 ml of a 6% carbohydrate (CHO) or taste-matched placebo (PLA) as well as no mouth rinse performed in the control (CON) trial.

RESULTS

TTE performance was significantly longer in both CHO and PLA trials when compared with the CON trial (54.7 ± 5.4 and 53.6 ± 5.1 vs. 48.4 ± 3.6 min, respectively; p < 0.001 and p = 0.012, respectively), but was not significantly different between CHO and PLA trials (p = 1.000). The rating of perceived exertion was not different between the CHO and PLA trials, however, was significantly affected when compared to the CON trial (p < 0.001). A similar effect was observed for perceived arousal level between the CHO and PLA trials to the CON trial. Core temperature, mean skin temperature and skin blood flow were not significantly different between the three trials (all p > 0.05). Similarly, plasma lactate and glucose as well as exercise heart rate were not influenced by the trials.

CONCLUSIONS

The present study demonstrates that mouth rinsing, whether carbohydrate or placebo, provides an ergogenic benefit to running endurance when compared to CON in a heat stress environment. Nevertheless, the results do not support the notion that rinsing a carbohydrate solution provides a greater advantage as previously described among non-heat acclimated individuals within a temperate condition.

Using beat frequency in music to adjust running cadence in recreational runners: A randomized multiple baseline design

Running with music has been shown to acutely change cadence. However, it is unclear if the increased cadence remains long-term when running without music in an in-field situation. The aim of this 12-week study was to investigate the effect of a 4-week music running program on cadence, speed and heartrate during and after the music running program. Seven recreational runners with a cadence of <170 steps per minute were randomly assigned to a baseline and post-intervention period of different durations. During the intervention phase, the participants ran with a musical beat that was 7.5-10% higher than their mean cadence at the start of the study. Cadence, heartrate and running speed were measured twice a week during a 5-kilometer run with a watch, and were analyzed using randomization tests and visual data inspection. Two participants dropped-out due to shortage of time (n = 1) and an acute calf injury (n = 1). Cadence significantly increased during the intervention period (+8.5%), and remained elevated during the post-intervention period (+7.9% (p = .001)) in comparison with the baseline period. Heartrate and running speed did not significantly change during any period. This study among five participants shows that four weeks of running with a musical beat that is 7.5-10% higher than the preferred cadence may be an effective and feasible intervention to increase running cadence. Importantly, the increased cadence occurred without simultaneous increases in running speed and heartrate, hereby potentially reducing mechanical loading without increasing metabolic load.HighlightsRunning with a musical rhythm that is higher than the preferred cadence leads to an increased running cadence, without increasing heartrate and running speed.This cadence remains elevated for at least three to five weeks after the music intervention period.All individuals showed a practically relevant increase in cadence during and after the intervention.

The Relative Importance of Training and Social Support for Runners' Performance: A Cross-Sectional Study

BACKGROUND

Running participation/performance is a complex system. Understanding the variables associated with these behaviors may help to increase population physical activity and improve performance. This study aimed to investigate social and training variables important for running performance using a network approach.

METHODS

This cross-sectional study sampled 1151 non-professional Brazilian runners of both sexes (women, 38.2%; men, 61.7%). A questionnaire was available for eligible participants using an online platform, and information regarding training (volume and running pace) and social variables (participation in a running event, participation in a running group, influence on running, runners in the family, and childhood sport) related to runners' performance was obtained. The Chi-square test and network model were estimated by sex.

RESULTS

Training characteristics tend to be clustered. For both sexes, the training volume node presented the highest expected influence in the network (1.69 for women and 2.16 for men). Centrality indicators of social variables show that sports childhood participation and the presence of runners in the family were the most important nodes of network connection for women and men, respectively.

CONCLUSION

Based on these findings, it was concluded that sports participation during childhood and the practice of running by other family members were important factors to connect variables in the network. These findings have practical applications for health policymakers, highlighting the need to develop educational programs to increase sports participation during childhood and within families.

Physical fitness throughout chemotherapy in children with acute lymphoblastic leukaemia and lymphoma

Acute lymphoblastic leukaemia/lymphoma (ALL/LBL) and its treatment interfere with normal physical functioning. However, it remains unclear how physical fitness (PF) is affected throughout treatment for ALL/LBL. Sixty-two patients (2.1 to 18.3 years) treated for ALL/LBL underwent four physical tests at nine timepoints from baseline up to 6 months post-treatment. We assessed muscle strength of the quadriceps and tibialis anterior, standing broad jump test (SBJ) for functional mobility and six-minute walk test (6MWT) for endurance. One-sample t-tests were used to compare our results to the norm at each timepoint. Norm-referenced Z-scores were predicted based on time, risk group and age at diagnosis, using linear mixed models. Quadriceps strength, SBJ and 6MWT scores were significantly lower than norm values at all timepoints from diagnosis up to 6 months after maintenance therapy. Significant decreases over time were encountered for quadriceps strength and SBJ, mainly occurring after induction therapy (F = 3.568, p < 0.001 and F = 2.699, p = 0.008, respectively). Age at diagnosis was a significant predictor for tibialis anterior strength (F = 5.266, p = 0.025), SBJ (F = 70.422, p < 0.001) and 6MWT (F = 15.890, p < 0.001) performances, with lower results in adolescents at all timepoints. Six months after treatment, quadriceps strength, 6MWT and SBJ scores remained below expected levels.

CONCLUSION

The decreased quadriceps strength, functional mobility and endurance at all timepoints, with a large deterioration following induction therapy, suggest the need for early interventions, specifically in the adolescent population. The continued low results 6 months after therapy emphasise the importance of long-term rehabilitation.

WHAT IS KNOWN

•Acute lymphoblastic leukaemia is the most common type of cancer among children, with increasing survival rates due to therapeutic improvements. •Acute lymphoblastic leukaemia/lymphoma and its treatment can cause muscle weakness, neuromuscular toxicity and a decreased cardiopulmonary fitness. Together with physical inactivity, this can result in a decreased physical fitness.

WHAT IS NEW

•Quadriceps strength, functional mobility and endurance are decreased during treatment for acute lymphoblastic leukaemia/lymphoma. The lowest measurements are observed after induction therapy, suggesting the need for early interventions. •We observed continued lower results for quadriceps strength, functional mobility and endurance at the end of treatment, up to 6 months after therapy, supporting the need for long-term rehabilitation.

Post-exercise skimmed milk, but not a sucrose beverage decreases energy intake at the next meal compared to a placebo beverage in active males

This study compared the appetite and energy intake effects of three post-exercise beverages at a subsequent post-exercise meal. On three occasions, ten active males: (mean ± sd) age 21.3 ± 1.2 y, V˙ O₂peak 58 ± 5 mL/kg/min) performed 30-min cycling at ∼60% V˙ O₂peak and five 4-min intervals at 85% V˙ O₂peak. Post-exercise, placebo (PLA: 57 kJ), skimmed milk (MILK: 1002 kJ) or sucrose (CHO: 1000 kJ) beverages (615 mL) were consumed. Sixty min post-beverage, subjects consumed an ad-libitum pasta lunch in a 30 min eating period. Subjective appetite and plasma acylated ghrelin and plasma glucose were determined pre-exercise, post-exercise and pre-meal, with sensory characteristics of beverages rated. Ad-libitum energy intake in MILK (6746 ± 2035) kJ) was lower than CHO (7762 ± 1921) kJ) (P = 0.038; dz = 0.98; large effect) and tended to be lower than PLA (7672 (2005) kJ) (P = 0.078; dz = 0.76; medium effect). Including energy consumed in beverages, energy intake was greater in CHO than PLA (P = 0.010; dz = 1.24; large effect) or MILK (P = 0.026; dz = 0.98; large effect), with PLA and MILK not different (P = 0.960; dz = 0.02; trial effect). Plasma ghrelin, plasma glucose and appetite were not different between trials. MILK was perceived thicker than CHO (P = 0.020; dz = 1.11; large effect) and creamier than PLA (P = 0.026; dz = 1.06; large effect). These results suggest that when energy balance is important for an exerciser, post-exercise skimmed milk ingestion reduces energy intake compared to a sucrose beverage and might therefore help facilitate recovery/adaptation without affecting energy balance.

Relationship between self-reported and objectively measured physical fitness in young men and women

Self-reported physical fitness has advantages in cost and time over objective methods, but previous studies demonstrate equivocal conclusions regarding validity. Methods for self-reporting are usually based on subjective judgements, while another approach includes performing field tests at home. The Norwegian military relies on the latter method for conscript selection, but its validity is unknown and should be investigated. In total 14,166 young men and women were included in the study. During conscript selection step one, the subjects were requested to perform 3,000 m run, push-up, pull-up and standing long jump tests at home, and report the results online ("self-reported measurements"). Step two took place at a conscript selection centre 1-18 months later. Here, the subjects completed a maximal treadmill test, seated medicine ball throw, pull-up and standing long jump tests ("objective measurements"). The results demonstrated correlation coefficients from 0.29 to 0.82 (P < 0.05) for self-reported vs. objective measurements, with the highest association found for self-reported and objectively measured pull-ups. Kappa values ranged from 0.05 to 0.34 (P < 0.05), with pull-ups demonstrating the highest agreement. More women than men over-reported their physical fitness. Among men and women indicating similar self-reported fitness, men's objective fitness was higher for all objective tests (effect sizes from 0.5 to 3.0). In conclusion, large variations in correlation coefficients were observed between self-reported and objectively measured physical fitness, while the kappa values indicated poor to fair agreement. The finding that more women than men over-reported their fitness level contradicts most previous studies.Highlights Low, moderate, and high correlations, and poor to fair agreements (kappa values), were observed between self-reported and objectively measured endurance and muscle strength variables.More women than men overreported their actual fitness level.Self-reported fitness based on performing field tests at home may be a feasible alternative to traditional methods which rely on self-perceived fitness.

Visceral sensitivity correlates with gastrointestinal symptoms in runners during training but does not negatively impact peri-exercise fueling

OBJECTIVES

This study aimed to evaluate the associations between several psychological factors (stress, anxiety, body vigilance, and visceral sensitivity) and gastrointestinal (GI) symptoms in runners, as well as whether any of these factors impact pre-exercise and during-exercise fueling.

METHODS

A virtual/online observational survey-based study with 82 (43 male and 39 female) runners was conducted. The Perceived Stress Scale (PSS)-14, State-Trait Inventory for Cognitive and Somatic Anxiety (STICSA-Trait), Body Vigilance Scale (BVS), and Visceral Sensitivity Index (VSI) were assessed. GI symptoms during runs over 1 week, as well as nutrient intakes from food and fluid consumed 4 h before and during runs, were recorded. GI problems were quantified as the percentage of runs that a participant reported at least one symptom  ≥ 3 out of 10.

RESULTS

VSI scores significantly correlated with the occurrence of all, upper, and lower GI symptoms during runs (ρ  =  0.32-0.38; p < 0.003), and these associations remained significant in partial correlation analyses. No significant associations were observed between GI symptom occurrence and scores on the BVS, PSS-14, or STICSA-Trait. In a subset of 72 runners with available nutrition data, intakes of energy, macronutrients, fluid, and caffeine before and during runs did not seem to be lower in those who had higher PSS-14, STICSA-Trait, BVS, or VSI scores, which was contrary to what was hypothesized.

CONCLUSIONS

Runners' visceral sensitivity levels associate with GI symptoms during training over a week, but the impact of this and other psychological factors on nutritional intake is uncertain, particularly around competition.

Relationships between cervical sagittal posture, muscle endurance, joint position sense, range of motion and level of smartphone addiction

BACKGROUND

Frequent smartphone use in a pathological way forces the user to adopt a compromised posture. This gradually results in changes to both the postural and musculoskeletal systems. This study's objectives were evaluation of head posture, muscle endurance, neck range of motion (ROM) and joint position sense in two separate smartphone user groups, one 'Addicted', the other 'Non-Addicted'.

METHODS

A sample of convenience (n = 60) was recruited from medical students (age 24.57 ± 4.38, 53.3% male) with a history of smartphones use > 2 h/day for 1-year. Based on the cut-off values of the smartphone addiction scale-short version (SAS-SV), participants were entered into each group (cut-off for male ≥ 31, female ≥ 33). Neck muscle endurance time, joint position error and cervical ROM, along with forward head posture parameters of craniovertebral angle (CVA), shoulder angle (SA), sagittal head angle (SHA) and forward head distance (FHD)) were evaluated. A Mann-Whitney test and Spearman correlation coefficient were used to determine the difference between groups and the correlations between variables.

RESULTS

The difference between 'Addicted' and 'Non-Addicted' groups was confirmed by the values for SAS-SV scores (25.23 ± 5.5 versus 43.9 ± 6.61) (p < 0.001). There were statistically significant differences between groups for the CVA and FHD parameters (p < 0.001). Further, the neck extensor muscle endurance (97 ± 3.79 versus 74.86 ± 2.23 s), was significantly different between groups (p = 0.010) but not after Bonferroni correction. There was no notable difference in the neck flexor muscle endurance, joint position error, SA, and SHA parameters between groups (p > 0.05).

CONCLUSIONS

There is a positive correlation between smartphone addiction and both decreased extensor muscle endurance and changes in neck postural alignment.

Can plyometric training change the pacing behaviour during 10-km running?

The effects of plyometric training (PT) on middle- and long-distance running performances are well established. However, its influence on pacing behaviour is still unclear. The aim of this study was to evaluate the effects of PT on pacing behaviour. In addition, verify whether the adaptations induced by PT would change ratings of perceived exertion (RPE) and/or affective feelings during the race. Twenty-eight male runners were assigned to two groups: control (C) and PT. PT held two weekly PT sessions for eight weeks. Drop jump (DJ) performance, 10-km running performance, pacing behaviour, RPE and affective feelings, VO_2peak, ventilatory thresholds (VT1 and VT2), peak treadmill speed (PTS), and running economy (RE) were measured. For group comparisons, a mixed model analysis for repeated measures, effect size (ES) and 90% confidence interval (90% CI) were calculated for all dependent variables. Significant differences pre-to-post was observed for PT group in DP (7.2%; p ≤ 0.01; ES = 0.56 (0.28-0.85)) and RE (4.5%; p ≤ 0.05; ES = -0.52 ((-0.73 to -0.31)) without changes in pacing behaviour. While PT was effective for improving DJ and RE, there is no evidence that pacing behaviour, RPE or affective feelings are directly affected by these adaptations during a 10-km time trial run.

Effects of training adaption in endurance athletes with atrial fibrillation: protocol for a multicentre randomised controlled trial

Endurance athletes have a high prevalence of atrial fibrillation (AF), probably caused by exercise-induced cardiac remodelling. Athletes diagnosed with AF are often advised to reduce the intensity and amount of training but the efficacy of this intervention has not been investigated in endurance athletes with AF. Effects of detraining in endurance athletes with atrial fibrillation is a two-arm international multicentre randomised (1:1) controlled trial on the effects of a period of training adaption on AF burden in endurance athletes with paroxysmal AF. One-hundred-and-twenty endurance athletes diagnosed with paroxysmal AF are randomised to a 16-week period of intervention (training adaption) or a control group. We define training adaption as training with a heart rate (HR) not exceeding 75% of the individual maximum HR (HRmax), and total duration of weekly training not exceeding 80% of the self-reported average before the study. The control group is instructed to uphold training intensity including sessions with HR ≥85% of HRmax. AF burden is monitored with insertable cardiac monitors, and training intensity with HR chest-straps and connected sports watches. The primary endpoint, AF burden, will be calculated as the cumulative duration of all AF episodes lasting ≥30sec divided by total duration of monitoring. Secondary endpoints include number of AF episodes, adherence to training adaption, exercise capacity, AF symptoms and health-related quality of life, echocardiographic signs of cardiac remodelling and risk of cardiac arrhythmias related to upholding training intensity.

Trial registration number

NCT04991337.

Study protocol version

4.7 (Date 9 March 2023).

Endurance training improves heart rate on-kinetics in women with subclinical hypothyroidism: a preliminary study

PURPOSE

The aim of the study was to evaluate the effect of endurance training on heart rate (HR) on-kinetics in patients with subclinical hypothyroidism (SH).

METHODS

Eighteen women were randomly assigned to trained group (TG) or control group (CG). Both groups performed three tests at 50 W in a cycle ergometer for 6 min. HR kinetics was obtained during the tests and the mean response time (MRT), which is equivalent to the time taken to reach 63% of the HR at steady state, was extracted. The TG was then submitted to 12 weeks of endurance training (50 min, 3x/week, intensity between 70 and 85% of the maximum HR predicted for the age). Statistical analysis was performed by the mixed analysis of variance.

RESULTS

At baseline, TG and CG were similar for TSH (7.7 ± 3.1 vs. 6.9 ± 3.3 mUI/L, p = 0.602, respectively) and FT4 (12.31 ± 1.51 vs. 12.20 ± 1.89 pmol/L, p = 0.889, respectively). After adjustment for body mass index and age, interactions between moment (baseline or after 12 weeks) and group (trained or control) were only significant for MRT (TG: 39.6 ± 10 to 28.9 ± 8.4 s, CG: 53.6 ± 20.3 to 55 ± 19.7 s, p = 0.001) and physical activity level (CG: 7.3 ± 0.7 to 8 ± 0.9, CG: 6.8 ± 0.8 in both moments, p = 0.005).

CONCLUSION

The preliminary results suggest that 12 weeks of endurance training improve HR on-kinetics and physical activity level in SH.

Marathon running and cell-cycle arrest biomarkers of acute kidney injury

OBJECTIVES

Endurance exercise is known to cause a rise in serum creatinine. It is not known to what extent this rise reflects renal stress and a potential acute kidney injury (AKI). Increases in Insulin Like Growth Factor Binding Protein 7 (IGFBP7) and Tissue Inhibitor of Metalloprotinases-2 (TIMP-2), urinary biomarkers of cell cycle arrest and renal stress, are associated with the development of AKI in clinical populations.

DESIGN

Repeated measures study.

METHODS

Runners were recruited at the 2019 Brighton Marathon (UK) and provided urine and blood samples at baseline, immediately post-race and 24 h post-race. Serum creatinine, urinary creatinine and urinary IGFBP7 and TIMP-2 were analysed from the samples.

RESULTS

Seventy nine participants (23 females, 56 males), aged 43 ± 10 yrs. (mean ± SD), finish time 243 ± 40mins were included for analysis. Serum creatinine increased over the race by 40 ± 26% (p < 0.001), TIMP-2 increased by 555 ± 697% (p < 0.001) and IGFBP7 increased by 1094 ± 1491% (p < 0.001) over the race. A subset of twenty-two participants supplied samples 24 h post-race, reporting values similar to baseline for all variables.

CONCLUSIONS

This study is the first to report large rises in IGFBP7 and TIMP-2 following marathon running. This suggests that rises in creatinine are not fully explained by changes in production and clearance and marathon running induces a state of kidney stress and potential injury.

Periodised Carbohydrate Intake Does Not Affect Substrate Oxidation but May Contribute to Endurance Capacity

The aim of this study was to investigate whether periodising carbohydrate intake around specific training sessions will enhance endurance training adaptations.Seventeen healthy recreationally endurance-trained males (n = 5) and females (n = 12) (27.5 ± 5.4 years) participated in a four-week training intervention. Participants were divided into two groups: FASTED (stayed fasted between evening high-intensity interval training session and low-intensity training session in the following morning) and FED (no restriction in food intake). Pre- and post-testing included peak oxygen uptake (VO_2peak), anaerobic capacity, and 60 min submaximal running tests. Fasted venous blood samples were drawn for the determination of triglyceride and glucose concentrations.VO_2peak increased in both FASTED (4.4 ± 3.0%, p = 0.001) and FED (4.6 ± 4.2%, p = 0.017), whereas maximal running velocity increased only in the FASTED (3.5 ± 2.7%, p = 0.002). Lactate concentrations in the anaerobic test after intervention were greater in FASTED than FED (p = 0.025-0.041). Running time in the anaerobic test was improved in FASTED (from 64.1 ± 15.6-86.3 ± 23.2 s, p < 0.001) but not in FED (from 56.4 ± 15.2-66.9 ± 21.3 s, p = 0.099). Substrate oxidation did not change after intervention in either of the groups (p = 0.052-0.597). Heart rate was lower in the submaximal running test in FASTED (p < 0.001) but not in FED (p = 0.097).Training with periodised carbohydrate availability does not have any effect on substrate oxidation. However, it seems to enhance the capacity to perform high-intensity exercise.

Are anthropometric characteristics powerful markers to predict the Cooper Run Test? Actual Caucasian data

Background

Cardiorespiratory fitness (CRF) is a powerful marker of cardiovascular health, especially in youth. Several field tests can provide accurate measurement of CRF, the Cooper Run Test (CRT) is generally preferred by physical education (PE) teachers and trainers. The CRT performance in adolescents has been compared to reference distance values, gender and age but the differences among the anthropometric characteristics of youth has not been evaluated. For these reasons, the aim of this study was to develop reference standards for CRT and evaluate possible correlations between biometric measurements and athletic performance.

Methods

This cross-sectional study involved a total of 9,477 children (4,615 girls) aged 11-14 years, freely recruited from North Italian middle schools. Mass, height and CRT performances were assessed in the morning during PE classes as scheduled (mornings-Monday to Friday). The anthropometric measures were collected at least 20 min before the CRT run test.

Results

We found a better CRT result in boys (p < 0.001), however a smaller SD in girls suggested a more homogeneous aerobic performance for girls (i.e., 371.12 m vs 282.00 m). In addition, the Shapiro-Wilk test showed a low p-value (p < 0.001) but the effect size (0.031 for boys and 0.022 for girls) was small enough that the correction on this parameter allows a practical assumption of normality for the distributions. A visual homoskedastic distribution in both sexes is evident for both body mass index (BMI), mass and VO₂ peak with respect to CRT results. In addition, there were low linear correlation coefficients for both BMI, mass and VO₂ peak compared to the CRT results, with a R2 < 0.5 for every covariate. The only visual heteroskedastic distribution was observed in regression between distance in CRT and age at peak high velocity.

Conclusions

Our findings suggested that anthropometric characteristics are not powerful markers to predict Cooper Run Test results in a well-mixed, unpolarized and unbiased pool of middle school boys and girls. PE teachers and trainers should prefer endurance tests over the use of indirect formulas to predict performance.

Trade-offs in muscle physiology in selectively bred high runner mice

A trade-off between locomotor speed and endurance occurs in various taxa, and is thought to be underpinned by a muscle-level trade-off. Among four replicate high runner (HR) lines of mice, selectively bred for voluntary wheel-running behavior, a negative correlation between average running speed and time spent running has evolved. We hypothesize that this trade-off is due to changes in muscle physiology. We studied the HR lines at generation 90, at which time one line (L3) is fixed for the mini-muscle phenotype, another is polymorphic (L6) and the others (L7, L8) lack mini-muscle individuals. We used in situ preparations to quantify the contractile properties of the triceps surae muscle complex. Maximal shortening velocity varied significantly, being lowest in mini-muscle mice (L3 mini=25.2 mm s-1, L6 mini=25.5 mm s-1), highest in normal-muscle mice L6 and L8 (40.4 and 50.3 mm s-1, respectively) and intermediate in normal-muscle L7 mice (37.2 mm s-1). Endurance, measured both as the slope of the decline in force and the proportion of initial force that could be sustained, also varied significantly. The slope was shallowest in mini-muscle mice (L3 mini=-0.00348, L6 mini=-0.00238), steepest in lines L6 and L8 (-0.01676 and -0.01853), and intermediate in L7 (-0.01145). Normalized sustained force was highest in mini-muscle mice (L3 mini=0.98, L6 mini=0.92) and lowest in L8 (0.36). There were significant, negative correlations between velocity and endurance metrics, indicating a muscle-level trade-off. However, this muscle-level trade-off does not seem to underpin the organismal-level speed and endurance trade-off previously reported as the ordering of the lines is reversed: the lines that run the fastest for the least time have the lowest muscle complex velocity and highest endurance.

Characteristics and usefulness of trunk muscle endurance tests on the Roman chair in healthy adults

Background

Adequate trunk muscle endurance is considered to be an important indicator of good low back stability; therefore, its assessment is needed when determining an individual's risk for back pain. Optimal tests to assess each trunk muscle group separately are difficult to find. The objective of this study was to verify if two groups of trunk muscle endurance tests (standard and alternative) show comparable results in terms of muscle endurance ratios, holding times and rated perceived effort to perform each test.

Methods

The study was designed as a quasi-experimental repeated-measures design. There was a single group of participants who took part in two different trunk muscle endurance testing. Sixty-eight healthy adult volunteers, aged 20-45 years (31.9 ± 7.2 years), without recent musculoskeletal injury or disorder participated in the study. All participants finished the study. Trunk muscle endurance tests as tested on the Roman chair (B tests) were compared with standard tests as suggested by McGill (A tests). Each group of tests consisted of an endurance test for trunk extensors, trunk flexors, and lateral trunk muscles for left and right side. The order of tests' performances was randomly assigned to each participant, whereby a participant did perform A and B tests in the same order. In each test of A and B the holding time was recorded and a perceived effort in each test performance was also assessed by participants. Post testing performance the four ratios of trunk muscles endurance comparison were calculated for each group of tests to determine if there is a good or poor ratio between muscles. Results of each participant were compared for trunk muscle endurance ratio calculations, holding times and rated perceived effort for A and B tests.

Results

Results showed comparable trunk muscle endurance ratios in the three ratios observed, except for the flexors:extensors ratio (A_FL:EX: 1.2 (IQR: 0.7-1.6) vs. B_FL:EX: 0.6 (IQR: 0.3-0.8); p < 0.001). As compared to A tests, holding times were significantly longer in B tests for the extensors (A_EX: 125.5 s (IQR: 104.8-182.8 s) vs. B_EX: 284.0 s (IQR: 213.0-342.3 s); p < 0.001) and lateral trunk muscles (A_L-LM: 61.0 s (IQR: 48.3-80.8 s) vs. B_L-LM: 131.5 s (IQR: 95.5-158.5 s); A_R-LM: 63.5 s (IQR: 45.8-77.3 s) vs. B_R-LM: 113.0 s (IQR: 86.3-148.8 s); p < 0.001), both were also rated as slightly easier to perform in the extensors (A_RPE-EX: 13 (IQR: 12.0-14.0) vs B_RPE-EX: 11 (IQR: 10.0-13.0); p_RPE-EX < 0.001) and lateral muscles testing (A_RPE-LM: 14.0 (IQR: 12.3-15.8) vs. B_RPE-LM: 13.0 (IQR: 12.0-15.0); p_RPE-LM = 0.001).

Conclusions

A and B tests are comparable in three of four trunk muscle endurance ratios, while longer holding times and lower perceived effort to perform were observed in most of the B tests. The Roman chair tests could be used as an alternative to standard tests.

Recovery of pelvic floor muscle strength and endurance 6 and 12 months postpartum in primiparous women-a prospective cohort study

INTRODUCTION AND HYPOTHESIS

To date there has been scant knowledge on the natural recovery of the pelvic floor muscles (PFMs) after childbirth. The aims of the present study were to investigate whether PFM variables at 6 and 12 months postpartum had returned to mid-pregnancy levels and assess risk factors for reduced recovery at 12 months postpartum.

METHODS

This was a prospective cohort study following 235 nulliparous pregnant women from mid-pregnancy to 12 months postpartum. Vaginal resting pressure (VRP), PFM strength and endurance were assessed by manometry at 22 weeks, 6 and 12 months postpartum. Multiple linear regression was used to address factors influencing PFM variables beyond birth mode.

RESULTS

Cesarean section was protective for change in PFM variables. From mid-pregnancy to 12 months postpartum there was a 20% reduction in VRP (p<0.001) and a 7.5 % reduction in PFM strength (p=0.007), and an increase of 9% in PFM endurance (p=0.002) in the normal vaginal birth. The instrumental vaginal group had a decline in VRP of 21% (p<0.001) and PFM strength of 15% (p=0.011), but no significant change in PFM endurance. Higher BMI at 12 months postpartum, longer second stage of labor, and major tears of the levator ani muscle had a negative influence on the PFM recovery beyond delivery mode.

CONCLUSIONS

At 12 months postpartum following vaginal delivery, the PFMs are not fully recovered compared with mid-pregnancy values. More follow-up physical therapy may be warranted in the postpartum period, especially for women with complicated vaginal births and higher BMI.

Daytime fluctuations of endurance performance in young soccer players: a randomized cross-over trial

OBJECTIVES

Fluctuations of physical performance and biological responses during a repetitive daily 24-h cycle are known as circadian rhythms. These circadian rhythms can influence the optimal time of day for endurance performance and related parameters which can be crucial in a variety of sports disciplines. The current study aimed to evaluate the daytime variations in endurance running performance in a 3.000-m field run and endurance running performance, blood lactate levels, and heart rate in an incremental treadmill test in adolescent soccer players.

RESULTS

In this study, 15 adolescent male soccer players (age: 18.0 ± 0.6 years) performed a 3.000-m run and an incremental treadmill test at 7:00-8:00 a.m. and 7:00-8:00 p.m. in a randomized cross-over manner. No significant variations after a Bonferroni correction were evident in endurance running performance, perceived exertion, blood lactate levels, and heart rates between the morning and the evening. Here, the largest effect size was observed for maximal blood lactate concentration (9.15 ± 2.18 mmol/l vs. 10.64 ± 2.30 mmol/l, p = .110, ES = 0.67). Therefore, endurance running performance and physiological responses during a field-based 3.000-m run and a laboratory-based test in young male soccer players indicated no evidence for daytime variations.

Endurance training does not affect maximum exertion/distance capacity in Anolis carolinensis lizards

Locomotor performance abilities are key predictors of survival and reproductive success in animals and understanding how selection targets them can provide insights into how morphology and physiology relate to fitness. But despite the large body of work on performance traits, along with well-established protocols to measure them, performance can be challenging to measure. Endurance, for instance, is commonly measured by recording how long an animal can run at a set pace until exhaustion, which is time-consuming and requires dedicated equipment. Consequently, exertion or distance capacity, measured as distance run until exhaustion when chased, is often used as a proxy for endurance, but the relationship between these two metrics has never been assessed even though they likely rely on different underlying physiological mechanisms. We tested experimentally for a relationship between endurance and exertion by training green anole lizards for sprinting and endurance and measuring whether exertion capacity responds to either type of training. Prior to training and across treatments, males displayed a mean exertion capacity of 14.08m (± 0.29m) and females 12.03m (± 3.52m), and respectively 14.78 (± 3.57m) and 12.19 (± 2.21m) after training. We found that exertion capacity is unaffected by either type of training in green anoles. We also show that a positive relationship between endurance and exertion capacity pre-training exists only in females and that this relationship is inconsistent among studies. Exertion should be studied as a locomotor trait in its own right and not as a proxy for endurance.

Health problems in national team cross-country skiers over a competitive season: a 17-week prospective cohort study

OBJECTIVE

Few long-term prospective studies have investigated health problems in elite competitive cross-country (XC) skiers. Hence, our objective was to compare the prevalence of health problems in national team XC skiers over a competitive season.

METHODS

Forty national team XC skiers participated in this prospective, observational study. Two groups were characterised according to performance level: senior (n=18, ~26 years old, 9 women) and development (n=22, ~21 years old, 9 women). The skiers reported all and substantial injuries and illnesses weekly for 17 consecutive weeks throughout the 2019/2020 competitive season using the Oslo Sports Trauma Research Center Questionnaire on Health Problems.

RESULTS

The average weekly prevalence of all and substantial health problems was 19% (95% CI: 16% to 22%) and 12% (95% CI: 9% to 15%), respectively, and was similar between senior and development level skiers (p>0.05). The injury prevalence was higher in senior versus development level skiers (12%, 95% CI: 9% to 15% vs 5%, 95% CI: 3% to 7%; p<0.001), while illnesses were less common (8%, 95% CI: 3% to 13% vs 13%, 95% CI: 9% to 17%, respectively; p=0.031). Illnesses accounted for 72% of all problems. The prevalence of all health problems was higher in female than in male skiers (23%, 95% CI: 19% to 27% vs 15%, 95% CI: 11% to 19%; p<0.003).

CONCLUSIONS

Health problems, especially illnesses, were relatively common, with approximately one in five skiers (19%) reporting at least one problem in any given week. Both performance level and sex influenced the prevalence of different types of health problems.

Associations between heart rate variability and maximal fat oxidation in two different cohorts of healthy sedentary adults

BACKGROUND AND AIMS

Resting heart rate variability (HRV) and maximal fat oxidation (MFO) during exercise are both considered as a noninvasive biomarkers for early detection of cardiovascular risk factors. Thus, this study aimed to analyze the relationship between resting HRV parameters and MFO during exercise, and the intensity of exercise that elicit MFO (Fat_max) in healthy sedentary adults.

METHODS AND RESULTS

A total of 103 healthy young adults (22.2 ± 2.3 years old, 67% female; from the ACTIBATE cohort) and 67 healthy middle-aged adults (53.1 ± 5.0 years old, 52% female; from the FIT-AGEING cohort) were included in this cross-sectional study. HRV was assessed using a Polar RS800CX heart rate monitor, while MFO and Fat_max were determined during a graded exercise treadmill test using indirect calorimetry. No significant associations were observed for healthy young adults (standardized β coefficients ranged from -0.063 to 0.094, and all P ≥ 0.347) and for middle-aged adults (standardized β coefficients ranged from -0.234 to 0.090, and all P ≥ 0.056). Nevertheless, only a weak association was observed between one HRV parameter in time-domain (the percentage of R-R intervals that shows a difference higher than 50 ms [pNN50]) and MFO in the cohort of middle-aged adults (β coefficient = -0.279, and P = 0.033).

CONCLUSION

The results of this study suggest that resting HRV parameters are not associated with MFO and Fat_max during exercise in two independent cohorts of healthy sedentary young and middle-aged adults, respectively.

Comparing walking and running in persistence hunting

It has been proposed that humans' exceptional locomotor endurance evolved partly with foraging in hot open habitats and subsequently about 2 million years ago with persistence hunting, for which endurance running was instrumental. However, persistence hunting by walking, if successful, could select for locomotor endurance even before the emergence of any running-related traits in human evolution. Using a heat exchange model validated here in 73 humans and 55 ungulates, we simulated persistence hunts for prey of three sizes (100, 250, and 400 kg) and three sweating capacities (nonsweating, low, high) at 6237 combinations of hunter's velocity (1-5 m s^-1, intermittent), air temperature (25-45 °C), relative humidity (30-90%), and start time (8:00-16:00). Our simulations predicted that walking would be successful in persistence hunting of low- and nonsweating prey, especially under hot and humid conditions. However, simulated persistence hunts by walking yielded a 30-74% lower success rate than hunts by running or intermittent running. In addition, despite requiring 10-30% less energy, successful simulated persistence hunts by walking were twice as long and resulted in greater exhaustion of the hunter than hunts by running and intermittent running. These shortcomings of pursuit by walking compared to running identified in our simulations could explain why there is only a single direct description of persistence hunting by walking among modern hunter-gatherers. Nevertheless, walking down prey could be a viable option for hominins who did not possess the endurance-running phenotype of the proposed first persistence hunter, Homo erectus. Our simulation results suggest that persistence hunting could select for both long-distance walking and endurance running and contribute to the evolution of locomotor endurance seen in modern humans.

Nutritional interventions for improving the endurance performance in athletes

Endurance refers to the ability of skeletal muscles to perform continuously withstanding the hardships of exercise. Endurance exercises have three phases: pre-, during-, and post-workout phase. The nutritional requirements that drive these phases vary on intensity, type of workout, individual's body composition, training, weather conditions, etc. Generally, the pre-workout phase requires glycogen synthesis and spare glycogen breakdown. While workout phase, requires rapid absorption of exogenous glucose, insulin release to transport glucose into muscle cells, replenish the loss of electrolytes, promote fluid retention, etc. However, post-workout phase requires quick amino acid absorption, muscle protein synthesis, repair of damaged muscle fibres and tendon, ameliorate inflammation, oxidative stress, etc. Therefore, nutritional sources that can help these metabolic requirements is recommended. In this review, various dietary interventions including timing and amount of nutrient consumption that can promote the above metabolic requirements that in turn support in improving the endurance potential in athletes are discussed.HIGHLIGHTSReview article describes nutritional requirements of endurance exercises.It also describes nutritional interventions to enhance the endurance potential in athletes.

Effects of self-selected versus motivational music on lower limb muscle strength and affective state in middle-aged adults

Background

Strength training plays a crucial role in promoting healthy ageing and music might affect how individuals perform and perceive strength exercises. This study aimed to investigate the effects of self-selected music (SSM) on muscle strength and affective states during maximal isometric contractions on a customized leg extension.

Methods

Twenty-six healthy middle-aged males (50.8 ± 8.4 years) performed maximal and endurance isometric strength tests under three different conditions: SSM, motivational music (MM), and control condition (CC). Peak force and Rate of Force Development (RFD) were assessed during the maximal isometric strength test. The isometric endurance test evaluated the mean force and a fatigue index. Moreover, Felt Arousal Scale (FAS) was administered before the strength protocol, whereas the Rate of Perceived Exertion (RPE) and Feeling Scale (FS) at the end of it.

Results

Mean force was significantly higher in the SSM (507.3 ± 132.2 N) than MM (476.3 ± 122.4 N, p < 0.01) and CC (484.6 ± 119.2 N, p = 0.03). FAS was significantly higher in the SSM (4.0 [1.3] than MM (3.0 [2.3], p < 0.01) and CC (3.0 [1.3], p < 0.01) conditions. FS was significantly higher in the SSM (4.0 [2.0] than MM (3.0 [1.3], p < 0.01) and CC (3.0 [1.3], p < 0.01) conditions. No significant differences were found for peak force, RFD, fatigue index, and RPE.

Conclusions

Listening to SSM seems to influence isometric endurance strength performance in middle-aged adults positively. Moreover, listening to SSM might improve individuals' affective states without affecting the level of perceived exertion.

Effects of school-based neuromuscular training on fundamental movement skills and physical fitness in children: a systematic review

Objectives

The primary purpose of this review was to clarify the effects of school-based integrated neuromuscular training (INT) on fundamental movement skills and physical fitness in children. The secondary purpose was to examine whether school-based INT intervention is superior to physical education (PE) intervention in enhancing motor skills and fitness.

Methods

A systematic literature search was performed in four electronic databases: PubMed, Web of Science, MEDLINE (EBSCOhost), and Cochrane Central Register of Controlled Trials. The last search was performed on December 21, 2021, and was limited to the English language, human species, and peer reviewed journals. Randomized controlled trials and cluster randomized controlled trials that examine the effects of school-based INT on motor skills and/or fitness in healthy children who were aged up to 14 years old were included. Moreover, studies included in this study should compare school-based INT-induced adaptions with those generated by PE interventions. Studies that involve athletic children and additional exercise training were excluded. The Physiotherapy Evidence Database (PEDro) scale was used to assess the quality of the study.

Results

Of 1,026 studies identified, seven original trials that meet the inclusion criteria were included in this review. Based on the PEDro scale, the PEDro score of seven studies was between six and eight points with a mean score of 5.29. Among the seven studies included in this study, four studies assessed physical fitness including muscular fitness (n = 4), speed (n = 3), endurance (n = 2), and flexibility (n = 2). Three studies examined the effects of INT on postural control and three studies explored its effects on motor skills. Concerning movement competence, significant and greater improvements in postural control and fundamental motor skills were observed following school-based INT interventions compared to PE intervention in two and three studies, respectively. Regarding physical fitness, neuromuscular training significantly increased muscular fitness, speed, endurance, flexibility in three, two, one, and one studies, respectively. However, only greater improvements in muscle fitness were observed in school-based INT group compared to PE group. The main limitations of this review were the lack of descriptions of training intensity and volume and the low methodological quality of the included studies.

Conclusion

This review provides evidence that school-based neuromuscular training programs are superior to PE lessons in improving postural control, fundamental motor skills and muscular strength. Therefore, INT could be incorporated into traditional physical education classes in school. Trial registration number: CRD42022297349.

The evolution of human fatigue resistance

Humans differ from African great apes in numerous respects, but the chief initial difference setting hominins on their unique evolutionary trajectory was habitual bipedalism. The two most widely supported selective forces for this adaptation are increased efficiency of locomotion and improved ability to feed in upright contexts. By 4 million years ago, hominins had evolved the ability to walk long distances but extreme selection for endurance capabilities likely occurred later in the genus Homo to help them forage, power scavenge and persistence hunt in hot, arid conditions. In this review we explore the hypothesis that to be effective long-distance walkers and especially runners, there would also have been a strong selective benefit among Homo to resist fatigue. Our hypothesis is that since fatigue is an important factor that limits the ability to perform endurance-based activities, fatigue resistance was likely an important target for selection during human evolution for improved endurance capabilities. We review the trade-offs between strength, power, and stamina in apes and Homo and discuss three biological systems that we hypothesize humans evolved adaptations for fatigue resistance: neurological, metabolic and thermoregulatory. We conclude that the evolution of endurance at the cost of strength and power likely also involved the evolution of mechanisms to resist fatigue.

Effect of Intensified Training on Cognitive Function, Psychological State & Performance in Trained Cyclists

AbstractAthletes often undertake intensified training loads prior to competition with the goal of functionally overreaching for temporary performance enhancement; however, little is known about the impact of this on cognitive function. The aim of this study was to investigate the effect of intensified training-induced fatigue on cognitive function, psychological state, and performance in trained cyclists. Twenty-three trained male cyclists were randomly assigned to an intensified training group or a control group for two-weeks, followed by a two-week taper period. At baseline, one-week, two-weeks and post-taper, participants undertook a series of cognitive, performance, mood, and recovery-stress assessments. The training intervention significantly increased training volume, load, and strain by 108%, 116% and 151% respectively. Peak and mean power output on a maximal test and time trial significantly decreased by 4.8% and 9.4% following the two-week training intervention compared to baseline, in addition to a 169% change in total mood disturbance and significant disruption to recovery-stress balance. No change in any cognitive measure was observed across the study period. Following a two-week taper, performance, mood, and well-being measures returned to baseline. Two weeks of intensified training resulted in overreaching as identified by performance and psychological measures. Cognitive function was not sensitive to intensified training promoting caution with its use as a measure for the early identification of overreaching.

The Effect of Sodium Alginate and Pectin Added to a Carbohydrate Beverage on Endurance Performance, Substrate Oxidation and Blood Glucose Concentration: A Systematic Review and Meta-analysis

INTRODUCTION

Scientific and public interest in the potential ergogenic effects of sodium alginate added to a carbohydrate (CHO) beverage has increased in the last ~ 5 years. Despite an extensive use of this technology by elite athletes and recent research into the potential effects, there has been no meta-analysis to objectively elucidate the effects of adding sodium alginate to a CHO beverage on parameters relevant to exercise performance and to highlight gaps in the literature.

METHODS

Three literature databases were systematically searched for studies investigating the effects of sodium alginate added to CHO beverage during prolonged, endurance exercise in healthy athletes. For the systematic review, the PROSPERO guidelines were followed, and risk assessment was made using the Cochrane collaboration's tool for assessing the risk of bias. Additionally, a random-effects meta-analysis model was used to determine the standardised mean difference between a CHO beverage containing sodium alginate and an isocaloric control for performance, whole-body CHO oxidation and blood glucose concentration.

RESULTS

Ten studies were reviewed systematically, of which seven were included within the meta-analysis. For each variable, there was homogeneity between studies for performance (n = 5 studies; I² = 0%), CHO oxidation (n = 7 studies; I² = 0%) and blood glucose concentration (n = 7 studies; I² = 0%). When compared with an isocaloric control, the meta-analysis demonstrated that there is no difference in performance (Z = 0.54, p = 0.59), CHO oxidation (Z = 0.34, p = 0.71) and blood glucose concentration (Z = 0.44, p = 0.66) when ingesting a CHO beverage containing sodium alginate. The systematic review revealed that several of the included studies did not use sufficient exercise intensity to elicit significant gastrointestinal disturbances or demonstrate any ergogenic benefit of CHO ingestion. Risk of bias was generally low across the included studies.

CONCLUSIONS

This systematic review and meta-analysis demonstrate that the current literature indicates no benefit of adding sodium alginate to a CHO beverage during exercise. Further research is required, however, before firm conclusions are drawn considering the range of exercise intensities, feeding rates and the apparent lack of benefit of CHO reported in the current literature investigating sodium alginate.

Influence of kinesiophobia on pain intensity, disability, muscle endurance, and position sense in patients with chronic low back pain-a case-control study

Background

Patients with chronic low back pain (CLBP) frequently present with kinesiophobia. Though large body of evidence reported the impact of kinesiophobia in patients with CLBP, there are paucity of studies in associating kinesiophobia to muscle endurance and position sense in patients with CLBP. The primary aim of the study is to compare the impact of kinesiophobia on lumbar extensor endurance, position sense in patient with CLBP, and asymptomatic individuals. Secondarily, we aim to examine the association between kinesiophobia and lumbar extensor endurance, position sense, pain intensity, and functional ability in patients with CLBP. Thirdly, we aim to assess the degree of association of various factors on CLBP, lumbar endurance, and position sense.

Material and methods

This case-control study will have 200 patients with CLBP and 400 controls. Kinesiophobia, lumbar endurance, and lumbar position sense will be assessed with Tampa Scale, Soren’s lumbar extensor test, and lumbar repositioning test respectively. Secondarily, the pain intensity will be assessed with visual analog scale and functional ability with Patient-specific Functional Scale in patients with CLBP. Lumbar endurance and joint position sense will be compared between subjects with and without kinesiophobia. Kinesiophobia scores will be compared with lumbar extensor endurance and proprioception joint position errors, pain intensity, and functional ability. Simple and multiple binary logistic regression will be used to determine crude and adjusted odd’s ratio for kinesiophobia, lumbar position sense and kinesiophobia, and lumbar endurance.

Discussion

The finding from this study can be generalized as this study has adequate sample size and subgroup analysis by adjusting the variables to draw a valid conclusion. The finding of this study will help the working physician to include assessment of kinesiophobia as part of musculoskeletal evaluation for patient with CLBP in a prospective diagnostic intervention.

Trial registration

ClinicalTrials.gov NCT05079893. Registered on 14 October 2021.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-022-06406-6.

Handcycling with concurrent lower body low-frequency electromyostimulation significantly increases acute oxygen uptake: implications for rehabilitation and prevention

Background

Acute increases in exercise-induced oxygen uptake (V̇O₂) is crucial for aerobic training adaptations and depends on how much muscle mass is involved during exercising. Thus, handcycling is per se limited for higher maximal oxygen uptakes (V̇O₂max) due to restricted muscle involvement. Handcycling with additional and simultaneous application of low-frequency electromyostimulation (EMS) to the lower extremities might be a promising stimulus to improve aerobic capacity in disabled and rehabilitative populations.

Method

Twenty-six healthy young adults (13 female, age: 23.4 ± 4.5 years, height: 1.77 ± 0.09 m, mass: 71.7 ± 16.7 kg) completed 4 ×10 minutes of sitting (SIT), sitting with concurrent EMS (EMS_SIT), handcycling (60 rpm, 1/2 bodyweight as resistance in watts) (HANDCYCLE) and handcycling with concurrent EMS of the lower extremities (EMS_HANDCYCLE). During EMS_SIT and EMS_HANDCYCLE, low frequency EMS (impulse frequency: 4Hz, impulse width: 350 µs, continuous stimulation) was applied to gluteal, quadriceps and calf muscles. The stimulation intensity was selected so that the perceived pain could be sustained for a duration of 10 minutes (gluteus: 80.0 ± 22.7 mA, quadriceps: 94.5 ± 20.5 mA, calves: 77.5 ± 19.1 mA).

Results

Significant mode-dependent changes of V̇O₂ were found (p < 0.001, η _p ² = 0.852). Subsequent post-hoc testing indicated significant difference between SIT vs. EMS_SIT (4.70 ± 0.75 vs. 10.61 ± 4.28 ml min^-1 kg^-1, p < 0.001), EMS_SIT vs. HANDCYCLE (10.61 ± 4.28 vs. 13.52 ± 1.40 ml min^-1 kg^-1, p = 0.005), and between HANDCYCLE vs. EMS_HANDCYCLE (13.52 ± 1.40 vs. 18.98 ± 4.89 ml min^-1 kg^-1, p = 0.001).

Conclusion

Handcycling with simultaneous lower body low-frequency EMS application elicits notably higher oxygen uptake during rest and moderately loaded handcycling and may serve as an additional cardiocirculatory training stimuli for improvements in aerobic capacity in wheelchair and rehabilitation settings.

Correlation and comparison of quadriceps endurance and knee joint position sense in individuals with and without unilateral knee osteoarthritis

Background

Knee osteoarthritis (KOA) is a painful degenerative joint disease that may limit activities of daily living. This study aimed to determine the relationship between quadriceps endurance and knee joint position sense (JPS) in KOA individuals and compare the quadriceps endurance and knee JPS with and without KOA.

Methods

This comparative cross-sectional study was conducted in medical rehabilitation clinics, King Khalid University, Saudi Arabia. This study recruited 50 individuals diagnosed with unilateral KOA (mean age = 67.10 ± 4.36 years) and 50 asymptomatic individuals (mean age = 66.50 ± 3.63 years). Quadriceps isometric endurance capacity (sec) was measured using a fatigue resistance test, and knee JPS (degrees) were assessed using a digital inclinometer and evaluated in sitting and standing positions.

Results

Quadriceps isometric endurance showed a significant moderate negative correlation with knee JPS in 20° of flexion (r = -0.48, p < 0.001); 40° of flexion: r = -0.62, p < 0.001; 60° of flexion: r = -0.58, p < 0.001) in sitting and 20° of flexion (r = -0.25, p = 0.084) in standing position in KOA individuals. When compared to the asymptomatic, the quadriceps endurance was lower (p < 0.001), and knee joint position errors were larger (p < 0.001) in KOA individuals.

Conclusion

Results of this study showed that quadriceps endurance capacity is negatively associated with knee JPS. KOA individuals demonstrated lower quadriceps endurance and larger JPS compared to asymptomatic.

12 weeks high intensity interval training versus moderate intensity continuous training in chronic low back pain subjects: a randomised single-blinded feasibility study

BACKGROUND

Currently, very little is known about the effects of an endurance high intensity interval training (HIIT) in chronic low back pain patients. Therefore, the feasibility and safety of the HIIT must be assessed first before Currently, very little is known about the effects of an endurance high intensity interval training in chronic low back pain patients. Therefore, the feasibility and safety of the HIIT has to be assessed first before it can be integrated safely into research and daily practice it can be integrated safely into research and daily practice. This study aims to answers the question if high intensity interval training and moderate intensity continuous training (MICT) have comparable adherence and feasibility.

METHODS

Participants (age from 29 to 69 years) with non-specific chronic low back pain were recruited in this randomised, single-blinded, allocation concealed, feasibility study. The participants trained 30 min on a cycle ergometer for 12 weeks. One group had HIIT and the other MICT.

RESULTS

Of 45 screened subjects 30 participated. The adherence rate was 94% in the HIIT group (median 0.94, IQR 0.23) versus 96% in the MICT group (median 0.96, IQR 0.08), without between-group differences: estimated median of the difference of - 0,01 [95% CI, - 0.11 to 0.06; p = 0.76]. Similar results in enjoyability (median 3, IQR 1 vs median 2, IQR 1.8) and willingness to continue the training (median 3, IQR 1 vs median 3, IQR 0.4). Both groups improved in pain and disability, without between-group differences in pain [median of the difference, 0.5; 95% CI, - 1 to 2; p = 0.95] nor in disability [median of the difference, 1.78; 95% CI, - 6.44 to 9.56; p = 0.64].

CONCLUSION

There were no differences in adherence rates. HIIT is as feasible as MICT in non-specific chronic low back pain and can be used in future larger trials to deepen the knowledge about HIIT in this specific population.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT04055545 . Registered 13 August 2019.

Walking endurance, muscle oxygen extraction, and perceived fatigability after overground locomotor training in incomplete spinal cord injury: A pilot study

Objective: The purpose of this study was to examine the effects of overground locomotor training (OLT) on walking endurance and gastrocnemius oxygen extraction in people with chronic cervical motor-incomplete spinal cord injury (SCI).Design: Prospective single-arm pre-post pilot study.Setting: Human Performance Research Laboratory.Participants: Adult men with traumatic chronic cervical SCI (n = 6; age = 30.8 ± 12.5).Intervention: Twenty-four sessions of structured OLT.Outcome measures: Walking endurance was determined during a constant work-rate time-to-exhaustion treadmill test. Normalized perceived fatigability was calculated by dividing subjective ratings of tiredness by walking time. Cardiorespiratory outcomes and muscle oxygen extraction were analyzed using breath-by-breath gas-exchange and near-infrared spectroscopy.Results: OLT resulted in large effects on walking endurance (1232 ± 446 s vs 1645 ± 255 s; d = 1.1; P = 0.045) and normalized perceived fatigability (5.3 ± 1.5 a.u. vs 3.6 ± 0.9 a.u.; d = 1.3; P = 0.033). Small-to-medium effects on absolute (2.8 ± 2.5 a.u. vs 4.2 ± 3.5 a.u.; d = 0.42; P = 0.035) and isotime (2.8 ± 2.5 a.u. vs 3.8 ± 3.0 a.u.; d = 0.33; P = 0.023) muscle oxygen extraction were also observed after OLT.Conclusion: These findings provide preliminary data supporting the potential for improved walking endurance, enhanced muscle O2 extraction, and reduced perceived fatigability in people with chronic cervical motor-incomplete SCI following the OLT program described in this study.

The Influence of L-menthol on Time Trial Running Performance in Recreational Runners

Purpose: This study investigated the effects of combined mouth rinse and topical application of L-menthol on perceptual responses and running performance under thermoneutral conditions (22 ± 2°C and 30-60% relative humidity). Methods: Twelve recreational male runners (age: 31.7 ± 3.8 years; age range: 27-39 years) completed a familiarization, a control test (CON) and two maximal 10-km time trials (counterbalanced randomized crossover design) performed in different days with a non-thermal cooling intervention (combined application of a L-menthol mouth rinse and topical L-menthol gel - MEN) or placebo (PLA). Performance and perceptual measures (thermal sensation, thermal comfort, ratings of perceived exertion and affective response) were recorded for every km completed in the 10-km test. Results: Performance time was lower in MEN (P = 0.03) and PLA (P = 0.003) compared to CON, but no differences were found between MEN vs PLA (P = 1.00). All perceptual responses increased over time in all conditions (P < 0.0001), but only the thermal sensation was lower (P = 0.01) in the MEN compared to CON. Conclusion: L-menthol strategies promote fresh sensations and may improve running performance in 10-km time trial in recreational runners, but the performance improvement could mainly be due to a placebo effect.

Inhaling salbutamol may decrease time to exhaustion in some contexts of heavy endurance performances

PURPOSE

To study the effect of inhaling a beta-agonist (salbutamol) compared to placebo on skiing and cycling performance in well-trained elite athletes.

METHODS

Three different exercise protocols were used, all with a cross-over double blind placebo-controlled design. Participants inhaled 800 µg salbutamol or a placebo prior to the test, which was repeated on a following day with the participants inhaling the other substance. Fifteen junior elite skiers performed four free-style high intensity sprints (1100 m/work time 3.5 - 4.5 min). Twelve elite cyclists carried out a short cycling protocol, starting with two 5 min submaximal workloads followed by a maximal intermittent performance test to exhaustion. Another 12 elite cyclists performed the maximal intermittent performance test to exhaustion after a 150 min long submaximal cycling protocol.

RESULTS

Group mean time for the ski sprints increased, with no difference between treatment groups. In the short cycling protocol time to exhaustion was 9.1% (95% CI 52 to 161) lower after inhaling salbutamol compared to placebo and in the long cycling protocol time to exhaustion was 9.1% (95% CI -121 to 267) lower after inhaling salbutamol compared to placebo. Blood lactate, heart rate and ventilation increased during submaximal exercise with salbutamol compared to placebo in the short cycling protocol (p < 0.05).

CONCLUSION

This study could not confirm any positive performance effects from inhaling 800 µg salbutamol compared to placebo in skiing and cycling high-intensity intermittent performance. Instead, time to exhaustion in the maximal intermittent performance test was lower in both cycling protocols.

Inflammatory cytokines and metabolic responses to high-intensity intermittent training: effect of the exercise intensity

To examine the effects of two high-intensity intermittent training (HIIT) programs of varying intensities (100% vs. 110% of maximal aerobic velocity [MAV]) on metabolic, hormonal and inflammatory markers in young men. Thirty-seven active male volunteers were randomly assigned into: HIIT experimental groups (100% MAV [EG₁₀₀, n = 9] and 110% MAV [EG₁₁₀, n = 9]) and a control groups (CG₁₀₀, n = 9 and CG₁₁₀, n = 9). Particpants performed high intesity intermittent exercise test (HIIE) at 100% or 110% MAV. Venous blood samples were obtained before, at the end of HIIE and at 15 min of recovery, and before and after 8 weeks of HIIT programs. After training, Glucose was lower (p < 0.01) in EG₁₀₀ (d = 0.72) and EG₁₁₀ (d = 1.20) at the end of HIIE, and at 15 min recovery only in EG₁₁₀ (d = 0.95). After training, Insulin and Cortisol were lower than before training in EG₁₀₀ and EG₁₁₀ at the end of HIIE (p < 0.001). After HIIT, IL-6 deceased (p < 0.001) in EG₁₀₀ (d = 1.43) and EG₁₁₀ (d = 1.56) at rest, at the end of HIIE (d = 1.03; d = 1.75, respectively) and at 15 min of recovery (d = 0.88;d = 1.7, respectively). This decrease was more robust (p < 0.05) in EG₁₁₀ compared to EG₁₀₀. After HIIT, TNF-α deceased (p < 0.001) in EG₁₀₀ (d = 1.43) and EG₁₁₀ (d = 0.60) at rest, at the end of HIIE (0.71 < d < 0.98) and at 15 min of recovery (0.70 < d < 2.78). HIIT with 110% MAV is more effective in young males on the improvements of some metabolic (Glucose), hormonal (Cortisol) and inflammatory (IL-6) markers at rest, at the end of HIIE and 15 min of recovery than training at 100 % MAV.

A critical review of critical power

The elegant concept of a hyperbolic relationship between power, velocity, or torque and time to exhaustion has rightfully captivated the imagination and inspired extensive research for over half a century. Theoretically, the relationship's asymptote along the time axis (critical power, velocity, or torque) indicates the exercise intensity that could be maintained for extended durations, or the "heavy-severe exercise boundary". Much more than a critical mass of the extensive accumulated evidence, however, has persistently shown the determined intensity of critical power and its variants as being too high to maintain for extended periods. The extensive scientific research devoted to the topic has almost exclusively centered around its relationships with various endurance parameters and performances, as well as the identification of procedural problems and how to mitigate them. The prevalent underlying premise has been that the observed discrepancies are mainly due to experimental 'noise' and procedural inconsistencies. Consequently, little or no effort has been directed at other perspectives such as trying to elucidate physiological reasons that possibly underly and account for those discrepancies. This review, therefore, will attempt to offer a new such perspective and point out the discrepancies' likely root causes.

Effects of non-surgical decompression therapy in addition to routine physical therapy on pain, range of motion, endurance, functional disability and quality of life versus routine physical therapy alone in patients with lumbar radiculopathy; a randomized controlled trial

Background

Lumbar radiculopathy is an extensively common complaint reported by patients of low back pain (LBP), resulting in several impairments. A comparatively novel technique, non-surgical spinal decompression (NSD), is introduced, which uses a sensitive computerized feedback mechanism and decompresses the spinal nerve roots through segmental distraction. The objective of this study was to determine the effects of NSD therapy in addition to routine physical therapy on pain, lumbar range of motion (ROM), functional disability, back muscle endurance (BME), and quality of life (QOL) in patients with lumbar radiculopathy.

Methods

A total of sixty patients with lumbar radiculopathy were randomly allocated into two groups, an experimental (n = 30) and a control (n = 30) group, through a computer-generated random number table. Baseline values were recorded before providing any treatment by using a visual analogue scale (VAS), Urdu version of Oswestry disability index (ODI-U), modified-modified Schober’s test (MMST), prone isometric chest raise test, and Short Form 36-Item Survey (SF-36) for measuring the pain at rest, functional disability, lumbar ROM, BME, and QOL, respectively. All patients received twelve treatment sessions over 4 weeks, and then all outcome measures were again recorded.

Results

By using the ANCOVA test, a statistically significant (p < 0.05) between-group improvement was observed in VAS, ODI-U, BME, lumbar ROM, role physical (RP), and bodily pain (BP) domains of SF-36, which was in favour of NSD therapy group. The between-group difference was 1.07 ± 0.32 cm (p < .001) for VAS, 5.65 ± 1.48 points (p < .001) for ODI-U, 13.93 ± 5.85 s (p = 0.002) for BME, 2.62 ± 0.27 cm (p < .001) for lumbar flexion, 0.96 ± 0.28 (p < .001) for lumbar extension, 5.77 ± 2.39 (p = 0.019) for RP and 6.33 ± 2.52 (p = 0.016) for BP domain of SF-36. For these outcomes, a medium to large effect size (d = 0.61–2.47, 95% CI: 0.09–3.14) was observed.

Conclusion

It was concluded that a combination of non-surgical spinal decompression therapy with routine physical therapy is more effective, statistically and clinically, than routine physical therapy alone in terms of improving pain, lumbar range of motion, back muscle endurance, functional disability, and physical role domain of quality of life, in patients with lumbar radiculopathy, following 4 weeks of treatment.

Trial registration

WHO Iranian registry of clinical trials (IRCT20190717044238N1) Dated: 23.12.2019.

Effects of caffeine chewing gum supplementation on exercise performance: a systematic review and meta-analysis

The aim of this systematic review with meta-analysis was to determine the effect of caffeine gum (Caff-gum) on exercise performance-related outcomes. Medline, EmBase, and SPORTSDiscus, and the register ClinicalTrials.gov were searched in March 2021, for studies assessing the effect of Caff-gum in placebo-controlled protocols involving healthy adults (i.e., with no chronic diseases or health conditions). Risk of bias was assessed using the RoB 2 tool. Random-effects meta-analyses using standardized mean differences (SMD) were performed to determine the effect of Caff-gum on exercise outcomes with several sub-analyses (training status, exercise type, timing and dose) for potential modifying factors. 14 studies were included, totaling 200 participants. There was a significant overall effect of Caff-gum compared to placebo (SMD = 0.21, 95%CI: 0.10-0.32; p = 0.001). Subgroup analysis showed improved performance for trained (SMD = 0.23, 95%CI: 0.08-0.37; p = 0.004), but not for untrained (SMD = 0.14, 95%CI: -0.02-0.29; p = 0.07) individuals. Caff-gum improved both endurance (SMD = 0.27, 95%CI: 0.12-0.42; p = 0.002) and strength/power (SMD = 0.20, 95%CI: 0.03-0.37; p = 0.03) performance outcomes. Caff-gum was ergogenic when consumed within 15 min prior to initiating exercise (SMD = 0.27, 95%CI: 0.07-0.4; p = 0.01), but not when provided >15 min prior (SMD=-0.48, 95%CI= -1.7-0.82; p = 0.25). There was no significant effect of Caff-gum with doses <3 mg/kg body mass (BM) (SMD = 0.20, 95%CI: -0.03-0.43; p = 0.07), but there was a significant effect when the dose was ≥3 mg/kg BM (SMD = 0.22, 95%CI: 0.07-0.37; p = 0.01). Caff-gum supplementation may be an effective ergogenic strategy for trained athletes involved in both endurance and strength/power exercise, using a recommended dose of ≥3 mg/kg BM consumed within 15 minutes before the exercise.

'The Good Doctor': the Making and Unmaking of the Physician Self in Contemporary South Africa

In this article we examine the figure of the doctor in animated debates around public sector medicine in contemporary South Africa. The loss of health professionals from the South African public system is a key contributor to the present healthcare crisis. South African medical schools have revised curricula to engage trainee doctors with a broader set of social concerns, but the disjunctures between training, health systems failures, and a high disease burden call into question whether junior doctors are adequately prepared or whether conditions of care extend beyond medical training. A concern with 'resilience' suggests a correct ethical relation to a putative obligation to provide care in a struggling system. By examining the ways in which trainee doctors are expected to 'cope' with the demands of medical practice, to adopt the correct moral posture in relation to the urgency of care, and to enact a desirable ethical relation to the broader social and political context of medical practice, we examine the picture of humanist concern that animates the subjectivities and techniques of the self called for by this training, and advocate for endurance as an alternative framework for understanding the political and ethical relations between doctors, patients and health systems.

Performance indicators and functional adaptive windows in competitive cyclists: effect of one-year strength and conditioning training programme

Changes and relationships between cycling performance indicators following a one-year strength and conditioning training have not been totally clarified. The aims of this study are to investigate (i) the effect of a combined one-year strength and conditioning training programme on performance indicators and the possible relationships between these indicators, and (ii) the existence of possible endurance-functional-adaptive windows (EFAWs) linked to changes in muscular strength and body composition markers. Functional and lactate threshold power (FTP and LTP), maximal strength (1RM) and body composition (body mass index [BMI], body cell mass [BCM] and phase angle [PA]) were measured at the beginning and the end of a one-year strength and conditioning training programme of thirty cyclists. Correlations, differences, and predictive analysis were performed among parameters. Significant differences were found between pre- and post-conditioning programme results for FTP, LTP, 1RM (p < 0.0001) and BCM (p = 0.038). When expressed as power output (W), FTP and LTP were significantly correlated with 1RM (r = 0.36, p = 0.005 and r = 0.37, p = 0.004, respectively), body mass (r = 0.30 and p = 0.02), BCM (r = 0.68, p < 0.001) and PA (r = 0.42 and 0.39, respectively and p < 0.001). When expressed as W·kg-¹, these power thresholds were strongly correlated with body mass (r = -0.56 and -0.61, respectively) and BMI (r = -0.57 and -0.61 respectively) with p < 0.001. Predictive polynomial regressions revealed possible endurance and strength adaptation zones. The present findings indicated beneficial impacts of one-year strength and conditioning training on cycling performance indicators, confirmed the correlation between performance indicators, and suggested the existence of different EFAWs. Strategies aiming to improve performance should consider cyclist characteristics and performance goals to achieve EFAWs and thereby enhance cycling performance.

Genomic characterization of the world's longest selection experiment in mouse reveals the complexity of polygenic traits

BACKGROUND

Long-term selection experiments are a powerful tool to understand the genetic background of complex traits. The longest of such experiments has been conducted in the Research Institute for Farm Animal Biology (FBN), generating extreme mouse lines with increased fertility, body mass, protein mass and endurance. For >140 generations, these lines have been maintained alongside an unselected control line, representing a valuable resource for understanding the genetic basis of polygenic traits. However, their history and genomes have not been reported in a comprehensive manner yet. Therefore, the aim of this study is to provide a summary of the breeding history and phenotypic traits of these lines along with their genomic characteristics. We further attempt to decipher the effects of the observed line-specific patterns of genetic variation on each of the selected traits.

RESULTS

Over the course of >140 generations, selection on the control line has given rise to two extremely fertile lines (>20 pups per litter each), two giant growth lines (one lean, one obese) and one long-distance running line. Whole genome sequencing analysis on 25 animals per line revealed line-specific patterns of genetic variation among lines, as well as high levels of homozygosity within lines. This high degree of distinctiveness results from the combined effects of long-term continuous selection, genetic drift, population bottleneck and isolation. Detection of line-specific patterns of genetic differentiation and structural variation revealed multiple candidate genes behind the improvement of the selected traits.

CONCLUSIONS

The genomes of the Dummerstorf trait-selected mouse lines display distinct patterns of genomic variation harbouring multiple trait-relevant genes. Low levels of within-line genetic diversity indicate that many of the beneficial alleles have arrived to fixation alongside with neutral alleles. This study represents the first step in deciphering the influence of selection and neutral evolutionary forces on the genomes of these extreme mouse lines and depicts the genetic complexity underlying polygenic traits.

Heart rate variability-guided training in professional runners: Effects on performance and vagal modulation

PURPOSE

To analyze the training structure following a heart rate variability (HRV) -guided training or traditional training protocol, determining their effects on the cardiovascular performance of professional endurance runners, and describing the vagal modulation interaction.

METHODS

This was an 8-week cluster-randomized controlled trial. Twelve professional endurance runners were randomly assigned to an HRV-guided training group (HRV-G; n = 6) or a traditional training group (TRAD-G; n = 6). The training methodology followed by the HRV-G was determined by their daily HRV scores. Training intensities were recorded daily. HRV4Training was used to register the rMSSD every morning and during a 60-second period. Cardiovascular outcomes were obtained through an incremental treadmill test. The primary outcome was the maximal oxygen uptake (VO_2max).

RESULTS

Total training volume was significantly higher in TRAD-G, but moderate intensity training was significantly higher in HRV-G (X ± SD_Dif=1.98 ± 0.1%; P = 0.006; d = 1.22) and low intensity training in TRAD-G (X ± SD_Dif=2.03 ± 0.74%; P = 0.004; d = 1.36). The maximal velocity increased significantly in HRV-G (P = 0.027, d = 0.66), while the respiratory exchange ratio increased in TRAD-G (P = 0.017, d = 1). There was a small effect on the LnRMSSD increment (P = 0.365, d = 0.4) in HRV-G. There were statistical inter-group differences in the ∆maximal heart rate when ∆LnrMSSD was considered as a covariable (F = 7.58; P = 0.025; d = 0.487). There were significant and indirect correlations of LnRMSSD_TEST with VO_2max (r =-0.656, P = 0.02), ∆LnrMSSD with ∆VO_2max (r = -0.606, P = 0.037), and ∆LnrMSSD_CV with ∆VENT (r = -0.790, P = 0.002).

CONCLUSIONS

higher HRV scores suggest better cardiovascular adaptations due to higher training intensities, favoring HRV as a measure to optimize individualized training in professional runners.

Association of muscle fiber composition with health and exercise-related traits in athletes and untrained subjects

Skeletal muscle is a heterogenous and metabolically active tissue, the composition of which is associated with multiple traits. The aim of the study was to determine whether there are additional health and exercise-related traits associated with muscle fiber composition in athletes and non-athletes. This study recruited 164 Russian participants (51 endurance and 48 power athletes; 65 controls). Vastus lateralis muscle fiber composition was assessed by immunohistochemistry. Slow-twitch muscle fiber percentage (STMF%) was significantly greater in endurance than power athletes and non-athletes, and in non-athlete females than males. STMF% was positively associated with athletes' training frequency, non-athletes' and endurance athletes' age, endurance athletes' competition level and chest depth, and power athletes' training age. STMF% was negatively associated with diastolic blood pressure in power athletes and with systolic blood pressure and reaction time in non-athletes. In all participants, STMF% was positively associated with age, tolerance to long distance exercise, chest depth and fracture incidence, and negatively with systolic blood pressure and resting heart rate. Age, sex and training frequency explained 10.6% and 13.2% of the variance in STMF% in endurance and power athletes, respectively. This is one of the most comprehensive studies involving athletes and untrained subjects and provides novel information concerning associations of increased STMF percentage with lower resting heart rate, better tolerance to long distances, faster reaction time and larger chest depth. On the other hand, the increased percentage of fast-twitch muscle fibers was associated with rare fracture incidence.

The beginning of success: Performance trends and cut-off values for junior and the U23 triathlon categories

Background

This study sought to determine cut-off values for each triathlon discipline to achieve podium in Junior (short distance; 750 m swim, 20 km cycle and 5 km run) and U23 (standard/Olympic distance; 1.5 km swim, 40 km cycle and 10 km run) triathlon events. Additionally, we aimed to investigate which discipline has the largest relationship with overall Junior and U23 triathlon performance, and the effect of sex and time in performance trends.

Methods

We included all data from Junior and U23 official races (International Triathlon Federation; ITU) of Junior (n = 3,314 finishes) and U23 (n = 5,092 finishes) categories held from 1999 to 2018.

Results

Men were significantly faster than women in both Junior (11.13%) and U23 (12.28%) categories. Swimming and cycling times were faster in 2009-2018 than in the 1999-2008 decade for men (3.36%; 6.49%), women junior (6.50%; 7.09%), men (0.15%; 3.46%) and women U23 (1.61%; 3.31%) respectively. Cycling was the discipline with the greatest influence on overall triathlon performance in Junior and U23 categories, regardless of sex or rank position. The cut-off values for the Junior category were (men/women): swimming, 9.2/9.4 min; cycling, 31.9/38.2 min; running, 16.8/18.9 min. U23's cut-off values were (men/women): swim, 18.0/19.4 min, cycling: 63.4/70.1 min; run, 33.9/38.7 min.

Conclusion

Cycling was the discipline with the greatest influence on overall performance for both men and women in Junior and U23 categories. Moreover, swimming and cycling performances increased over the years for both sexes.

Cost of transport, but not gluteus medius and red blood cells monocarboxylate-transporters density differentiated Brazilian Sport Horses at two performance levels

Cost of transport (COT) and monocarboxylate transporters (MCTs) could affect the ability to perform fast actions during a jumping discipline. This study aimed to compare the COT and evaluate the MCT1, MCT4, and their auxiliary protein CD147 content in the gluteus medius and RBCs of Brazilian sport horses (BH), a breed developed for jumping competitions, with low-level (LL) or intermediate-level (IL) jumping capacities. The physiological difference between the horses was assessed by an incremental jump test (IJT), in which the cost of lactate (COT_LAC) and heart rate (COT_HR) of running were determined for each animal by the ratio between each variable and the running speed. Western blotting was performed on muscle and RBC membranes to quantify MCT1, MCT4, and CD147. IL showed lower COT_LAC and COT_HR than LL at all jumping heights. The amount of MCT1, MCT4, and CD147 found in muscle and RBCs were not dependent on performance level. Muscle MCT4 and MCT1 were correlated positively with CD147. We conclude that the relatively small differences between performances did not relevantly influence MCT expression in BH. While MCT analyses are inaccessible for most trainers and veterinarians, the cost of transport measurements is a feasible and sensitive tool to distinguish intermediate and low-level jumping horses.

Morphological and mechanical properties of lower limbs in competitive racewalkers: Associations with performance

Racewalking is an unconventional form of competitive gait that elicits a unique loading profile on lower limb muscles and tendons. This study mapped the structural and mechanical properties of lower limbs in competitive racewalkers and made associations with World Athletics competition performance points. Fourteen international racewalkers (seven men, seven women) were recruited for this study. Static ultrasonography was used to quantify muscle and tendon morphological characteristics. An isokinetic dynamometer was used to measure passive musculotendinous stiffness of the triceps surae, isometric (seven knee/ankle angle combinations) and isokinetic (four angular velocities) strength parameters in the plantarflexors and dorsiflexors, and isokinetic knee flexion and extension strength at five angular velocities. Correlations were found between performance and fascicle length of gastrocnemius medialis (r = -0.569, p = 0.034), dorsiflexor strength at 120°/s (r = 0.649, p = 0.016) and knee flexor strength at 30°/s (r = 0.632, p = 0.020). No associations were found for isometric plantarflexion or passive stiffness properties. Overall, the study showed various morphological and mechanical properties are associated with performance in competitive racewalkers. These associations seem to be related to the specific and unique biomechanical characteristics of racewalking.

Exercising under particulate matter exposure: Providing theoretical support for lung deposition and its relationship with COVID-19

The aim of the present study was to investigate lung particulate matter (PM) deposition during endurance exercise and provide a new insight concerning how SARS-CoV-2 could be carried into the respiratory tract. The anatomical and physiological characteristics of the Human Respiratory Tract model were considered for modeling the lung PM deposition during exercise. The Monte Carlo method was performed to randomly generate different values of PM concentrations (1.0, 2.5, and 10.0 μm), minute ventilation, and duration of exercise at moderate, heavy, and severe exercise intensity domains. Compared to moderate and severe intensities, during heavy exercise (75-115 L‧min-1, duration of 10.0-60.0 min) there is greater lung deposition in the bronchiolar region (p < 0.01). In turn, there is greater deposition per minute of exercise at the severe intensity domain (115.0-145.0 L‧min^-1, duration of 10.0-20.0 min, p < 0.01). Considering that SARs-CoV-2 could be adsorbed on the particles, exercising under PM exposure, mainly at the severe domain, could be harmful concerning the virus. In conclusion, beyond the traditional minute ventilation assumption, there is a time vs intensity dependence for PM deposition, whereby the severe domain presents greater deposition per minute of exercise. The results observed for PM deposition are alarming since SARs-CoV-2 could be adsorbed by particles and carried into the deeper respiratory tract.

Differential effects of ergometer-cycling and Whole-Body-Vibration training on serological BDNF and IGF-1 in the treatment of adolescent depression - is there an impact of BDNFp.Val66Met variants?

BACKGROUND

Pathogenesis and treatment of adolescent depression may be influenced by growth-factors, including brain-derived neurotrophic factor (BDNF) and insulin-like growth factor 1 (IGF-1). We investigated, if treatment response to two different add-on exercise-therapies in juvenile depression, differ in the changes of BDNF and IGF-1 serology. A subgroup analysis for genetic variations in BDNF p.Val66Met-variants was added.

METHODS

Included subjects in the study (N = 64), aged 13 to 17 years, were diagnosed with major depression, controls received inpatient treatment as usual (TAU). Intervention groups performed as add-on to TAU two different forms of exercise-therapy: endurance ergometer cycling (EC) and muscle strengthening whole body vibration (WBV). We expected both exercise-forms to increase BDNF and IGF-1 serology and by this pathway to improve depression scores significantly stronger than the control group.

RESULTS

None of the experimental groups showed significant changes in BDNF between measurement time points. However, after 6 weeks exercise, BDNF of both intervention groups were significantly higher compared to TAU,. The IGF-1 increase after 6 weeks intervention was significant for EC only. No correlations of BDNF and IGF-1 to depression scores were found. Group analysis in BDNF p.Val66Met variants showed a trend for better response in depression scores to exercise-treatment for the Val66Val group.

LIMITATIONS

A small sample size, the non-randomized controls and the neglect of psychosocial factors have to be considered as limitations.

CONCLUSIONS

Endurance and muscle strengthening trainings seem to influence serological BDNF and IGF-1 differentially. However, the changes in growth factors did not correlate to the decreases in depression scores. BDNF p.Val66Val variant seems to be more receptive for exercise treatment. Identifying biomarkers (growth factors, genetic variants) in adolescent depression could help to develop tailored treatment strategies.