Oxygen kinetics and modelling of time to exhaustion whilst running at various velocities at maximal oxygen uptake

Adaptations to Optimized Interval Training in Soccer Players: A Comparative Analysis of Standardized Methods for Individualizing Interval Interventions

Accurately prescribing supramaximal interval training facilitates targeting desired physiological adaptations. This study compared the homogeneity of adaptations in cardiorespiratory parameters to supramaximal [i.e., intensities beyond maximal aerobic speed (MAS)] interval interventions prescribed using anaerobic speed reserve (ASR), the speed attained at the end of 30-15 Intermittent Fitness Test (VIFT), and MAS. Using repeated-measures factorial design, and during the off-season phase of the athletes' yearly training cycle, thirty national-level soccer players (age = 19 ± 1.6 years; body mass = 78.9 ± 1.6 kg; height = 179 ± 4.7 cm; Body fat = 11 ± 0.9%) were randomized to interventions consisting of 2 sets of 6, 7, 8, 7, 8, and 9-min intervals (from 1st to 6th week), including 15 s running at Δ%20ASR (MAS + 0.2 × ASR), 120%MAS, or 95%VIFT followed by 15 s passive recovery. All ASR, VIFT, and MAS programs sufficiently stimulated adaptive mechanisms, improving relative maximal oxygen uptake [V̇O2max (p < 0.05; ES = 1.6, 1.2, and 1.1, respectively)], absolute V̇O2max (p < 0.05; ES = 1.5, 1.1, and 0.7), ventilation [V̇E (p < 0.05; ES = 1.6, 1.1, and 1.1)], O2 pulse [V̇O2/HR (p < 0.05; ES = 1.4, 1.1, and 0.6)], first and second ventilatory threshold [VT1 (p < 0.05; ES = 0.7, 0.8, and 0.7) and VT2 (p < 0.05; ES = 1.1, 1.1, and 0.8)], cardiac output [Q̇max (p = 1.5, 1.0, and 0.7)], and stroke volume [SVmax (p < 0.05; ES = 0.9, 0.7, and 0.5)]. Although there was no between-group difference for the change in the abovementioned variables over time, supramaximal interval training prescribed using ASR and VIFT resulted in a lower coefficient of variation [CV (inter-individual variability)] in physiological adaptations compared to exercise intensity determined as a proportion of MAS. Expressing the intensity of supramaximal interval programs according to the athlete's ASR and VIFT would assist in accurately prescribing interventions and facilitate imposing mechanical and related physiological stimulus according to the athletes' physiological ceiling. Such an approach leads to identical stimulation across athletes with differing profiles and potentially facilitates more homogenized adaptations.

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Peak Running Velocity vs. Critical Speed: Which One Is Better to Prescribe Endurance Training to Recreational Runners?

ABSTRACT

Figueiredo, DH, Figueiredo, DH, Manoel, FA, and Machado, FA. Peak running velocity vs. critical speed: which one is better to prescribe endurance training to recreational runners? J Strength Cond Res 37(9): 1783-1788, 2023-This study aimed to evaluate the effects of 5 weeks of training prescribed by peak running velocity obtained on the track (Vpeak_TR) and their respective time limit (Tlim), as well as by critical speed (CS), on physiological and endurance performance parameters in recreational runners. Twenty-two male runners were distributed into a Vpeak_TR group (GVP) and CS group (GCS) with a predefined program, alternating moderate-intensity continuous training and high-intensity interval training. Maximum oxygen uptake (V̇O2max), and its respective velocity (vV̇O2max), Vpeak_TR, Tlim at 100% Vpeak_TR, 5-km running performance, CS, and D' (maximum distance covered above CS) were assessed at pretraining and posttraining period. There was a significant increase from pretraining to posttraining in Vpeak_TR (GVP = 4.5 ± 3.1% vs. GCS = 7.5 ± 4.2%), vV̇O2max (GVP = 3.9 ± 3.8% vs. GCS = 8.6 ± 6.7%), and mean velocity 5-km (GVP = 5.6 ± 3.3% vs. GCS = 7.3 ± 3.5%) and decrease in 5-km time (GVP = -5.1 ± 3.0% vs. GCS = -6.8 ± 3.0%). CS and V̇O2max significantly improved in GCS (9.3 ± 8.4% and 6.0 ± 6.8%, respectively), with no difference for GVP (2.8 ± 5.6% and 1.3 ± 8.4%, respectively). No differences were observed between groups for all variables. These findings give further supports to the notion that both variables obtained on the track are valid tools to prescribed training in recreational runners.

Oxygen Uptake Kinetics and Time Limit at Maximal Aerobic Workload in Tethered Swimming

This study aimed to apply an incremental tethered swimming test (ITT) with workloads (WL) based on individual rates of front crawl mean tethered force (Fmean) for the identification of the upper boundary of heavy exercise (by means of respiratory compensation point, RCP), and therefore to describe oxygen uptake kinetics (VO₂k) and time limit (t_Lim) responses to WL corresponding to peak oxygen uptake (WLVO_2peak). Sixteen swimmers of both sexes (17.6 ± 3.8 years old, 175.8 ± 9.2 cm, and 68.5 ± 10.6 kg) performed the ITT until exhaustion, attached to a weight-bearing pulley-rope system for the measurements of gas exchange threshold (GET), RCP, and VO_2peak. The WL was increased by 5% from 30 to 70% of Fmean at every minute, with Fmean being measured by a load cell attached to the swimmers during an all-out 30 s front crawl bout. The pulmonary gas exchange was sampled breath by breath, and the mathematical description of VO₂k used a first-order exponential with time delay (TD) on the average of two rest-to-work transitions at WLVO_2peak. The mean VO_2peak approached 50.2 ± 6.2 mL·kg^-1·min^-1 and GET and RCP attained (respectively) 67.4 ± 7.3% and 87.4 ± 3.4% VO_2peak. The average t_Lim was 329.5 ± 63.6 s for both sexes, and all swimmers attained VO_2peak (100.4 ± 3.8%) when considering the primary response of VO₂ (A_1' = 91.8 ± 6.7%VO_2peak) associated with the VO₂ slow component (SC) of 10.7 ± 6.7% of end-exercise VO₂, with time constants of 24.4 ± 9.8 s for A_1' and 149.3 ± 29.1 s for SC. Negative correlations were observed for t_Lim to VO_2peak, WLVO_2peak, GET, RCP, and EEVO₂ (r = -0.55, -0.59, -0.58, -0.53, and -0.50). Thus, the VO₂k during tethered swimming at WLVO_2peak reproduced the physiological responses corresponding to a severe domain. The findings also demonstrated that t_Lim was inversely related to aerobic conditioning indexes and to the ability to adjust oxidative metabolism to match target VO₂ demand during exercise.

Determination, measurement, and validation of maximal aerobic speed

This study determined Maximal Aerobic Speed (MAS) at a speed that utilizes maximal aerobic and minimal anaerobic contributions. This method of determining MAS was compared between endurance (ET) and sprint (ST) trained athletes. Nineteen and 21 healthy participants were selected for the determination and validation of MAS respectively. All athletes completed five exercise sessions in the laboratory. Participants validating MAS also ran an all-out 5000 m at the track. Oxygen uptake at MAS was at 96.09 ± 2.51% maximal oxygen consumption ([Formula: see text]). MAS had a significantly higher correlation with velocity at lactate threshold (vLT), critical speed, 5000 m, time-to-exhaustion velocity at delta 50 in addition to 5% velocity at [Formula: see text] (T_limυΔ50 + 5%v[Formula: see text]), and Vsub%95 (υΔ50 or υΔ50 + 5%v[Formula: see text]) compared with v[Formula: see text], and predicted 5000 m speed (R² = 0.90, p < 0.001) and vLT (R² = 0.96, p < 0.001). ET athletes achieved significantly higher MAS (16.07 ± 1.58 km·h^-1 vs. 12.77 ± 0.81 km·h^-1, p ≤ 0.001) and maximal aerobic energy (E_MAS) (52.87 ± 5.35 ml·kg^-1·min^-1 vs. 46.42 ± 3.38 ml·kg^-1·min^-1, p = 0.005) and significantly shorter duration at MAS (ET: 678.59 ± 165.44 s; ST: 840.28 ± 164.97 s, p = 0.039). ST athletes had significantly higher maximal speed (35.21 ± 1.90 km·h^-1, p < 0.001) at a significantly longer distance (41.05 ± 3.14 m, p = 0.003) in the 50 m sprint run test. Significant differences were also observed in 50 m sprint performance (p < 0.001), and peak post-exercise blood lactate (p = 0.005). This study demonstrates that MAS is more accurate at a percentage of v[Formula: see text] than at v[Formula: see text]. The accurate calculation of MAS can be used to predict running performances with lower errors (Running Energy Reserve Index Paper).

Running Energy Reserve Index (RERI) as a new model for assessment and prediction of world, elite, sub-elite, and collegiate running performances

The purpose of this study was to utilize the Running Energy Reserve Index (RERI) model and two-trial procedure to predict all-out athletic performances. Twenty-nine trained athletes tested for differences between RERI_E and RERI_spd (hypothesis 1). Six sprint trained (ST), six middle distance (MD), and six endurance trained (ET) athletes were selected to test for differences in the value of the constant. The prediction of all-out run performances using the RERI model (hypothesis 2) and two treadmill trials procedure (hypothesis 3) were tested on eighteen trained athletes. Lastly, three trained athletes were utilized to predict all-out running performances utilizing two track trials equation (hypothesis 3). RERI_E and RERI_spd were significantly different between ST, MD, and ET athletes. The RERI_E model with a fixed c_E value of 0.0185 s^-1 predicted all-out running performances to within an average of 2.39 ± 2.04% (R² = 0.99, n_T = 252) for all athletes, with treadmill trials to within an average of 2.26 ± 1.89% (R² = 0.99, n_T = 203) and track trials to within an average of 2.95 ± 2.51% (R² = 0.99, n_T = 49). The two trials equations predicted all-out track performances to within errors of 2.43%. The RERI model may be accurate in determining running performances of 200 m and 5000 m, and treadmill performances ranging between 5 and 1340 s with a high level of accuracy. In addition, the two-trial procedure can be used to determine short and middle distance running performances of athletes and world-class runners.

Aerobic high-intensity intervals are superior to improve V̇O2max compared with sprint intervals in well-trained men

Maximal oxygen uptake (V̇O_2max ) may be the single most important factor for long-distance running performance. Interval training, enabling high intensity, is forwarded as the format that yields the largest increase in V̇O_2max . However, it is uncertain if an optimal outcome on V̇O_2max , anaerobic capacity, and running performance is provided by training with a high aerobic intensity or high overall intensity. Thus, we randomized 48 aerobically well-trained men (23 ± 3 years) to three commonly applied interval protocols, one with high aerobic intensity (HIIT) and two with high absolute intensity (sprint interval training; SIT), 3× week for 8 weeks: (1) HIIT: 4 × 4 min at ~95% maximal aerobic speed (MAS) with 3 min active breaks. (2) SIT: 8 × 20 s at ~150% MAS with 10 s passive breaks. (3) SIT: 10 × 30 s at ~175% MAS with 3.5 min active breaks. V̇O_2max increased more (p < 0.001) following HIIT, 4 × 4 min (6.5 ± 2.4%, p < 0.001) than SIT, 8 × 20 s (3.3 ± 2.4%, p < 0.001) and SIT, 10 × 30 s (n.s.). This was accompanied by a larger (p < 0.05) increase in stroke volume (O₂ -pulse) following HIIT, 4 × 4 min (8.1 ± 4.1%, p < 0.001) compared with SIT, 8 × 20 s (3.8 ± 4.2%, p < 0.01) and SIT, 10 × 30 (n.s.). Anaerobic capacity (maximal accumulated oxygen deficit) increased following SIT, 8 × 20 s (p < 0.05), but not after HIIT, 4 × 4 min, nor SIT, 10 × 30 s. Long-distance (3000-m) endurance performance increased (p < 0.05-p < 0.001) in all groups (HIIT, 4 × 4 min: 5.9 ± 3.2%; SIT, 8 × 20 s: 4.1 ± 3.7%; SIT, 10 × 30 s: 2.2 ± 2.2%), with HIIT increasing more than SIT, 10 × 30 s (p < 0.05). Sprint (300-m) performance exhibited within-group increases in SIT, 8 × 20 s (4.4 ± 2.0%) and SIT, 10 × 30 s (3.3 ± 2.8%). In conclusion, HIIT improves V̇O_2max more than SIT. Given the importance of V̇O_2max for most endurance performance scenarios, HIIT should typically be the chosen interval format.

Usefulness of V˙O2 Kinetics and Biomechanical Parameters as Predictors of Athlete's Performance in 800 m Running Race

Incremental tests to exhaustion have been usually employed as the “gold standard” to establish the fitness level of athletes. However, during real competition in many sport disciplines, exertion is not characterized by an increasing effort until failure. The purpose of this preliminary study was to add new evidence regarding the usability of parameters obtained from an on-field testing in 800 m running athletes. V˙O2 kinetics (mean, amplitude, phase time, and phase start time) and biomechanical parameters (velocity, stride frequency, and stride length) were analyzed in eight athletes during a maximal 800 m running race test. Our results showed that only the peak of blood lactate concentration after the 800 m test was correlated with the race time (p = 0.047). The race time was positively associated with both the phase duration and phase start time (all p-values < 0.05). Conversely, race time was negatively correlated with velocity, stride frequency, and amplitude (p-values < 0.05). Our results reveal that jointly studying the V˙O2 kinetics and biomechanical parameters during a maximal 800 m running race test is a useful tool to predict the athlete’s upcoming performance and improve the planning and control of the training process of 800 m running athletes.

Endurance Training Increases the Running Performance of Untrained Men without Changing the Mitochondrial Volume Density in the Gastrocnemius Muscle

The activity and quantity of mitochondrial proteins and the mitochondrial volume density (Mito_VD) are higher in trained muscles; however, the underlying mechanisms remain unclear. Our goal was to determine if 20 weeks’ endurance training simultaneously increases running performance, the amount and activity of mitochondrial proteins, and Mito_VD in the gastrocnemius muscle in humans. Eight healthy, untrained young men completed a 20-week moderate-intensity running training program. The training increased the mean speed of a 1500 m run by 14.0% (p = 0.008) and the running speed at 85% of maximal heart rate by 9.6% (p = 0.008). In the gastrocnemius muscle, training significantly increased mitochondrial dynamics markers, i.e., peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) by 23%, mitochondrial transcription factor A (TFAM) by 29%, optic artrophy-1 (OPA1) by 31% and mitochondrial fission factor (MFF) by 44%, and voltage-dependent anion channel 1 (VDAC1) by 30%. Furthermore, training increased the amount and maximal activity of citrate synthase (CS) by 10% and 65%, respectively, and the amount and maximal activity of cytochrome c oxidase (COX) by 57% and 42%, respectively, but had no effect on the total Mito_VD in the gastrocnemius muscle. We concluded that not Mito_VD per se, but mitochondrial COX activity (reflecting oxidative phosphorylation activity), should be regarded as a biomarker of muscle adaptation to endurance training in beginner runners.

Acute Effects of Energy Drink on Autonomic and Cardiovascular Parameters Recovery in Individuals with Different Cardiorespiratory Fitness: A Randomized, Crossover, Double-Blind and Placebo-Controlled Trial

Fundamento

Tem-se sugerido que o consumo de bebidas energéticas (BEs) possa afetar a atividade cardiovascular.

Objetivos

Investigar os efeitos agudos da ingestão de BE sobre a variabilidade da frequência cardíaca (VFC) recuperação cardiovascular após exercício aeróbico moderado em homens de diferentes capacidades cardiorrespiratórias.

Métodos

Este é um estudo randomizado, duplo cego, crossover, controlado por placebo. Vinte e oito jovens adultos foram divididos em dois grupos de acordo com o pico de consumo de oxigênio (pico de VO2): (1) pico de VO2 alto (AO) – pico de VO2 > 52,15 mL/Kg/min, e (2) pico de VO2 baixo (BO) - pico de VO2 <52,15 mL/Kg/min. Os indivíduos de ambos os grupos foram submetidos a dois protocolos de exercícios em ordem aleatória: exercício moderado aeróbico (60% de pico de VO2) após a ingestão de 250 mL de água (protocolo placebo) ou 250 mL de BE (protocolo BE). Durante os testes de exercício, foram registrados valores de parâmetros cardiorrespiratórios e de VFC.

Resultados

Foram observadas diferenças significativas para o índice de LF (unidades normalizadas) entre “repouso” e “Rec1” nos grupos de AO e BO durante o protocolo BE. Para a razão LF/HF, foram observadas diferenças significativas entre “repouso” e Rec1 nos grupos AO e BO nos protocolos BE.

Conclusão

A ingestão aguda de BE retardou a recuperação da frequência cardíaca após o exercício em indivíduos com capacidade cardiorrespiratória baixa e indivíduos com capacidade cardiorrespiratória alta.

Validation of a Speech Database for Assessing College Students' Physical Competence under the Concept of Physical Literacy

This study developed a speech database for assessing one of the elements of physical literacy—physical competence. Thirty-one healthy and native Cantonese speakers were instructed to read a material aloud after various exercises. The speech database contained four types of speech, which were collected at rest and after three exercises of the Canadian Assessment of Physical Literacy 2nd Edition. To show the possibility of detecting each exercise state, a support vector machine (SVM) was trained on the acoustic features. Two speech feature sets, the extended Geneva Minimalistic Acoustic Parameter Set (eGeMAPS) and Computational Paralinguistics Challenge (ComParE), were utilized to perform speech signal processing. The results showed that the two stage four-class SVM were better than the stage one. The performances of both feature sets could achieve 70% accuracy (unweighted average recall (UAR)) in the three-class model after five-fold cross-validation. The UAR result of the resting and vigorous state on the two-class model running with the ComParE feature set was 97%, and the UAR of the resting and moderate state was 74%. This study introduced the process of constructing a speech database and a method that can achieve the short-time automatic classification of physical states. Future work on this corpus, including the prediction of the physical competence of young people, comparison of speech features with other age groups and further spectral analysis, are suggested.

Maximal Time Spent at VO2max from Sprint to the Marathon

Until recently, it was thought that maximal oxygen uptake (VO_2max) was elicited only in middle-distance events and not the sprint or marathon distances. We tested the hypothesis that VO_2max can be elicited in both the sprint and marathon distances and that the fraction of time spent at VO_2max is not significantly different between distances. Methods: Seventy-eight well-trained males (mean [SD] age: 32 [13]; weight: 73 [9] kg; height: 1.80 [0.8] m) performed the University of Montreal Track Test using a portable respiratory gas sampling system to measure a baseline VO_2max. Each participant ran one or two different distances (100 m, 200 m, 800 m, 1500 m, 3000 m, 10 km or marathon) in which they are specialists. Results: VO_2max was elicited and sustained in all distances tested. The time limit (Tlim) at VO_2max on a relative scale of the total time (Tlim at VO_2max%Ttot) during the sprint, middle-distance, and 1500 m was not significantly different (p > 0.05). The relevant time spent at VO_2max was only a factor for performance in the 3000 m group, where the Tlim at VO_2max%Ttot was the highest (51.4 [18.3], r = 0.86, p = 0.003). Conclusions: By focusing on the solicitation of VO_2max, we demonstrated that the maintenance of VO_2max is possible in the sprint, middle, and marathon distances.

Exercise above the maximal lactate steady state does not elicit a V̇O2 slow component that leads to attainment of V̇O2max

There is a pervasive belief that the severe-intensity domain is defined as work rates above the power associated with a maximal lactate steady state (MLSS) and by a oxygen uptake (V̇O₂) response that demonstrates a rapid increase (primary phase) followed by a slower increase (slow component), which leads to maximal oxygen uptake (V̇O_2max) if exercise is continued long enough. Fifteen university students performed 5 to 7 tests to calculate power at MLSS (154 ± 29 W). The tests included 30 min of exercise at each of 3 work rates: (i) below (-2 ± 1 W) power at MLSS, (ii) above (+4 ± 1 W) the power at MLSS, and (iii) well above (+19 ± 8 W) power at MLSS. The V̇O₂ response in each test was described using mathematical modeling. Contrary to expectation, the response at the supra-MLSS work rates had not 2, but 3, distinct phases: the primary phase and the slow component, plus a "delayed" third phase, which emerged after ∼15 min. V̇O_2max was not attained at supra-MLSS work rates. These results challenge commonly held beliefs about definitions and descriptions of exercise intensity domains. Novelty: The V̇O₂ response at work rates that are too high to sustain a lactate steady state but not high enough to elicit V̇O_2max features not 2, but 3, distinct phases. There is no consensus on whether intensity domains should be defined by their boundaries or by the responses they engender.

Sigmoidal VO2 on-kinetics: A new pattern in VO2 responses at the lower district of extreme exercise domain

The aim of the study was to analyse the VO₂ on-kinetics belonging to the work rates within the lower district of extreme exercise domain. Maximal O₂ utilisation and peak power outputs of eight well-trained cyclists were revealed by multisession trails. Critical threshold (CT) as the lower boundary of severe domain and aerobic limit power (ALP) as the upper boundary of severe domain were determined by multisession constant-load exercises. VO₂ on-kinetics over time were best fitted by multicomponent exponential models described by an initial concave-up response known as cardio-dynamic phase (τ = 18.2 ± 2.88 s; a = 1.56 ± 0.39 L·min^-1) before a primary concave-up phase (τ = 35.4 ± 12.4 s; a = 1.53 ± 0.36 L·min^-1), and then a slow component in two of the participants (τ = 80.8 ± 37 s; a = 0.47 ± 0.05 L·min^-1) or without a slow component in six of the participants during exercises performed at 50 W above the CT (R²≥0.96; SEE ≤ 0.24; p < 0.001). However, VO₂ on-kinetics over time belonging to exercises performed at 50 W above the ALP were best fitted by sigmoidal model (R²≥0.98; SEE ≤ 0.14; p < 0.001) in comparison with linear (R² = 0.37-0.66; SEE = 0.46-0.64; p < 0.01), or exponential functions (p> 0.05). Indeed, during those exercises, a short period of convex-up response (τ = 16.8 ± 3.1 s; a = 1.72 ± 0.39 L·min^-1) was determined just before a concave-up primary phase in VO₂ over time (τ = 24.6 ± 5.86 s; a = 1.31 ± 0.20 L·min^-1). It was shown that multicomponent exponential trend in VO₂ transformed into a sigmoidal shape, once the work rate exceeded the upper boundary of severe exercise domain.

Energy Drink before Exercise Did Not Affect Autonomic Recovery Following Moderate Aerobic Exercise: A Crossover, Randomized and Controlled Trial

Introduction: Energy drink (ED) intake could initiate physiological changes owing to its stimulant characteristics and, it improves endurance and athletic performance. We evaluated the acute effects of ED on autonomic heart rate (HR) control during recovery after a session of submaximal aerobic exercise.Method: The study was completed by submitting 29 healthy males between 18 and 30 years old to three conventions: (A) Maximum exercise test by the adapted Bruce protocol; (B) Placebo protocol (PP) - water intake 15 minutes prior to exercise, rest in dorsal decubitus for 15 minutes followed by 5 minutes of treadmill running at 1% inclination, initial speed of 5 km/h for 5 minutes 25 minutes with 60% of the velocity consistent to the maximum oxygen consumption (VO2max), and finally 60 minutes of recovery at rest in the supine position; (C) Experimental protocol (PE) - similar to PP previously, but with ED intake 15 minutes before physical exercise. The time, frequency and geometric indexes of HR variability (HRV) were inspected before and after exercise.Results: There was a significant (p < 0.05, <5%) effect on the HRV index (HR-nu and ms², LF-nu and ms², LF/HF, SD1, SDNN and RMSSD), indicating a reduction in HRV in the first 5 minutes after exercise in both protocols (PP and PE). Yet, no protocol interaction was detected, suggesting no effect of ED on HRV throughout recovery after submaximal aerobic exercise.Conclusion: There was no significant effect of ED on the autonomic control of HR in the recovery phase after submaximal aerobic exercise.

Housing conditions modulate spontaneous physical activity, feeding behavior, aerobic running capacity and adiposity in C57BL/6J mice

There is evidence of reduced adiposity in rodents living in a large cages (LC) as compared to animals housed in small cages (SC). Because spontaneous physical activity (SPA) provides an important portion of the total daily energy expenditure, an increase of SPA in rodents kept in LC could explain their reduced body fat accumulation. The relationship between SPA and components of physical fitness (i.e. aerobic and anaerobic fitness and body leanness) has not been previously determined. We examined the effects of eight weeks of LC exposure on SPA, body composition, feeding behavior, as well as aerobic and anaerobic running capacity in adult C57BL/6J mice. Male mice were housed in cages of two different sizes for 8 weeks: a small (SC, n = 10) and large (LC n = 10) cages with 1320 cm² and 4800 cm² floor space, respectively. SPA was measured gravimetrically, and food and water intake were recorded daily. Mice had critical velocity (CV) and anaerobic running capacity (ARC) evaluated at the beginning, middle course (4th week) and at the end of study (8th week). Despite non-significant differences in each week LC-mice were more active than SC-mice by considering all SPA values obtained in the entire period of 8 weeks. The difference in SPA over the whole day was mainly due to light phase activity, but also due to activity at dark period (from 6 pm to 9 pm and from 5 am to 6 am). LC-mice also exhibited higher food and water intake over the entire 8-wk period. LC-mice had lower content of fat mass (% of the eviscerated carcass) than SC-mice (SC: 8.4 ± 0.4 vs LC: 6.3 ± 0.3, p < 0.05). LC-mice also exhibited reduced epididymal fat pads (% of body mass) compared to SC-mice (SC: 1.3 ± 0.1 vs LC: 0.9 ± 0.1, p < 0.05) and retroperitoneal fat pads (SC: 0.4 ± 0.05 vs LC: 0.2 ± 0.02, p < 0.05). The LC-group showed significantly higher critical velocity than SC-group at the fourth week (SC: 14.9 ± 0.6 m·min^-1 vs LC: 18.0 ± 0.3 m·min^-1, p < 0.05) and eighth week (SC: 17.1 ± 0.5 m·min^-1 vs LC: 18.8 ± 0.6 m·min^-1, p < 0.05). Our findings demonstrate that eight weeks of LC housing increases SPA of C57BL/6J mice, and this may lead to reduced fat accumulation as well as higher aerobic fitness. Importantly, our study implies that SC limits SPA, possibly generating experimental artifacts in long-term rodent studies.

The Effect of Caffeine Ingestion and Carbohydrate Mouth Rinse on High-Intensity Running Performance

The aim of the current study was to investigate whether carbohydrate mouth rinsing works synergistically with caffeine to augment high-intensity running in a fed state. Eight participants completed a total of three trials; (1) placebo (PLA) trial (placebo capsule + placebo mouth rinse), (2) caffeine (CAF) trial (400 mg caffeine + placebo mouth rinse) and (3) carbohydrate mouth rinse + caffeine (CMR + CAF) trial (400 mg caffeine + 6% carbohydrate mouth rinse). Each trial consisted of a 45 min steady-state run at 65% VO_2max, followed by 90% VO_2max high-intensity intervals (HIIT) at 1 min and subsequently by a 1 min recovery walking at 6 km·h⁻¹, until exhaustion. Both CAF (46.8 ± 20.1 min) and CMR + CAF (46.9 ± 18.4 min) time to exhaustion were significantly greater than the PLA group (36.2 ± 14.8 min, p < 0.001). Post hoc analysis revealed that there was a significant increase in time to exhaustion between PLA and CMR + CAF (p = 0.006) and PLA and CAF (p = 0.017) but not between CAF and CMR + CAF (p = 0.99). In conclusion, we provide novel data that suggest that caffeine alone would likely suffice as an ergogenic aid during high-intensity running while in a fed state.

It's Harder to Push, When I Have to Push Hard-Physical Exertion and Fatigue Changes Reasoning and Decision-Making on Hypothetical Moral Dilemmas in Males

Despite the prevalence of physical exertion and fatigue during military, firefighting and disaster medicine operations, sports or even daily life, their acute effects on moral reasoning and moral decision-making have never been systematically investigated. To test the effects of physical exertion on moral reasoning and moral decision-making, we administered a moral dilemma task to 32 male participants during a moderate or high intensity cycling intervention. Participants in the high intensity cycling group tended to show more non-utilitarian reasoning and more non-utilitarian decision-making on impersonal but not on personal dilemmas than participants in the moderate intensity cycling group. Exercise-induced exertion and fatigue, thus, shifted moral reasoning and moral decision-making in a non-utilitarian rather than utilitarian direction, presumably due to an exercise-induced limitation of prefrontally mediated executive resources that are more relevant for utilitarian than non-utilitarian reasoning and decision-making.

A minimal power model for human running performance

Models for human running performances of various complexities and underlying principles have been proposed, often combining data from world record performances and bio-energetic facts of human physiology. The purpose of this work is to develop a novel, minimal and universal model for human running performance that employs a relative metabolic power scale. The main component is a self-consistency relation for the time dependent maximal power output. The analytic approach presented here is the first to derive the observed logarithmic scaling between world (and other) record running speeds and times from basic principles of metabolic power supply. Our hypothesis is that various female and male record performances (world, national) and also personal best performances of individual runners for distances from 800m to the marathon are excellently described by this model. Indeed, we confirm this hypothesis with mean errors of (often much) less than 1%. The model defines endurance in a way that demonstrates symmetry between long and short racing events that are separated by a characteristic time scale comparable to the time over which a runner can sustain maximal oxygen uptake. As an application of our model, we derive personalized characteristic race speeds for different durations and distances.

Effect of Jump Interval Training on Kinematics of the Lower Limbs and Running Economy

Ache-Dias, J, Pupo, JD, Dellagrana, RA, Teixeira, AS, Mochizuki, L, and Moro, ARP. Effect of jump interval training on kinematics of the lower limbs and running economy. J Strength Cond Res 32(2): 416-422, 2017-This study analyzed the effects of the addition of jump interval training (JIT) to continuous endurance training (40-minute running at 70% of peak aerobic velocity, 3 times per week for 4 weeks) on kinematic variables and running economy (RE) during submaximal constant-load running. Eighteen recreational runners, randomized into control group (CG) or experimental group (EG) performed the endurance training. In addition, the EG performed the JIT twice per week, which consisted of 4-6 bouts of continuous vertical jumping (30 seconds) with 5-minute intervals. The oxygen consumption (V[Combining Dot Above]O2) during the submaximal test (performed at 9 km·h) was similar before (EG: 38.48 ± 2.75 ml·kg·min; CG: 36.45 ± 2.70 ml·kg·min) and after training (EG: 37.42 ± 2.54 ml·kg·min; CG: 35.81 ± 3.10 ml·kg·min). No effect of training, group, or interaction (p > 0.05) was found for RE. There was no interaction or group effect for the kinematic variables (p > 0.05). Most of the kinematic variables had a training effect for both groups (support time [p ≤ 0.05]; step rate [SR; p ≤ 0.05]; and step length [SL; p ≤ 0.05]). In addition, according to the practical significance analysis (percentage chances of a better/trivial/worse effect), important effects in leg stiffness (73/25/2), vertical stiffness (73/25/2), SR (71/27/2), and SL (64/33/3) were found for the EG. No significant relationship between RE and stiffness were found for EG and CG. In conclusion, the results suggest that JIT induces important changes in the kinematics of the lower limbs of recreational runners, but the changes do not affect RE.

Gas exchange kinetics following concentric-eccentric isokinetic arm and leg exercise

PURPOSE

To evaluate the effects of exercise velocity (60, 150, 240deg∙s^-1) and muscle mass (arm vs leg) on changes in gas exchange and arterio-venous oxygen content difference (avDO₂) following high-intensity concentric-eccentric isokinetic exercise.

METHODS

Fourteen subjects (26.9±3.1years) performed a 3×20-repetition isokinetic exercise protocol. Recovery beat-to-beat cardiac output (CO) and breath-by-breath gas exchange were recorded to determine post-exercise half-time (t_1/2) for oxygen uptake (V˙O₂pulm), carbon dioxide output (V˙CO₂pulm), and ventilation (V˙_E).

RESULTS

Significant differences of the t_1/2 values were identified between 60 and 150deg∙s^-1. Significant differences in the t_1/2 values were observed between V˙O₂pulm and V˙CO₂pulm and between V˙CO₂pulm and V˙_E. The time to attain the first avDO₂-peak showed significant differences between arm and leg exercise.

CONCLUSIONS

The present study illustrates, that V˙O₂pulm kinetics are distorted due to non-linear CO dynamics. Therefore, it has to be taken into account, that V˙O₂pulm may not be a valuable surrogate for muscular oxygen uptake kinetics in the recovery phases.

Intramuscular determinants of the ability to recover work capacity above critical power

PURPOSE

The primary purpose of this investigation was to compare the recovery of the W' to the recovery of intramuscular substrates and metabolites using (31)P- and (1)H-magnetic resonance spectroscopy.

METHODS

Ten healthy recreationally trained subjects were tested to determine critical power (CP) and W' for single-leg-extensor exercise. They subsequently exercised in the bore of a 1.5-T MRI scanner at a supra-CP work rate. Following exhaustion, the subjects rested in place for 1, 2, 5 or 7 min, and then repeated the effort. The temporal course of W' recovery was estimated, which was then compared to the recovery of creatine phosphate [PCr], pH, carnosine content, and to the output of a novel derivation of the W' BAL model.

RESULTS

W' recovery closely correlated with the predictions of the novel model (r = 0.97, p = 0.03). [PCr] recovered faster [Formula: see text] than W' [Formula: see text] The W' available for the second exercise bout was directly correlated with the difference between [PCr] at the beginning of the work bout and [PCr] at exhaustion (r = 0.99, p = 0.005). Nonlinear regression revealed an inverse curvilinear relationship between carnosine concentration and the W' t 1/2 (r (2) = 0.55).

CONCLUSION

The kinetics of W' recovery in single-leg-extensor exercise is comparable to that observed in whole-body exercise, suggesting a conserved mechanism. The extent to which the recovery of the W' can be directly attributed to the recovery of [PCr] is unclear. The relationship of the W' to muscle carnosine content suggests novel future avenues of investigation.

VO2 kinetics and metabolic contributions whilst swimming at 95, 100, and 105% of the velocity at VO2max

A bioenergetical analysis of swimming at intensities near competitive distances is inexistent. It was aimed to compare the transient VO₂ kinetics responses and metabolic contributions whilst swimming at different velocities around VO_2max⁡. 12 trained male swimmers performed (i) an incremental protocol to determine the velocity at VO_2max⁡ (vVO_2max⁡) and (ii) three square wave exercises from rest to 95, 100, and 105% of vVO_2max⁡. VO₂ was directly measured using a telemetric portable gas analyser and its kinetics analysed through a double-exponential model. Metabolic contributions were assessed through the sum of three energy components. No differences were observed in the fast component response (τ₁—15, 18, and 16 s, A₁—36, 34, and 37 mL · kg⁻¹ · min⁡⁻¹, and Gain—32, 29, and 30 mL · min⁡⁻¹ at 95, 100, and 105% of the vVO_2max⁡, resp.) but A2 was higher in 95 and 100% compared to 105% intensity (480.76 ± 247.01, 452.18 ± 217.04, and 147.04 ± 60.40 mL · min⁡⁻¹, resp.). The aerobic energy contribution increased with the time sustained (83 ± 5, 74 ± 6, and 59 ± 7% for 95, 100, and 105%, resp.). The adjustment of the cardiovascular and/or pulmonary systems that determine O₂ delivery and diffusion to the exercising muscles did not change with changing intensity, with the exception of VO₂ slow component kinetics metabolic profiles.

Exercise: Kinetic considerations for gas exchange

The activities of daily living typically occur at metabolic rates below the maximum rate of aerobic energy production. Such activity is characteristic of the nonsteady state, where energy demands, and consequential physiological responses, are in constant flux. The dynamics of the integrated physiological processes during these activities determine the degree to which exercise can be supported through rates of O₂ utilization and CO₂ clearance appropriate for their demands and, as such, provide a physiological framework for the notion of exercise intensity. The rate at which O₂ exchange responds to meet the changing energy demands of exercise--its kinetics--is dependent on the ability of the pulmonary, circulatory, and muscle bioenergetic systems to respond appropriately. Slow response kinetics in pulmonary O₂ uptake predispose toward a greater necessity for substrate-level energy supply, processes that are limited in their capacity, challenge system homeostasis and hence contribute to exercise intolerance. This review provides a physiological systems perspective of pulmonary gas exchange kinetics: from an integrative view on the control of muscle oxygen consumption kinetics to the dissociation of cellular respiration from its pulmonary expression by the circulatory dynamics and the gas capacitance of the lungs, blood, and tissues. The intensity dependence of gas exchange kinetics is discussed in relation to constant, intermittent, and ramped work rate changes. The influence of heterogeneity in the kinetic matching of O₂ delivery to utilization is presented in reference to exercise tolerance in endurance-trained athletes, the elderly, and patients with chronic heart or lung disease.

Changes in the anaerobic threshold in an annual cycle of sport training of young soccer players

The aim of the study was to assess changes in the anaerobic threshold of young soccer players in an annual training cycle. A group of highly trained 15-18 year old players of KKS Lech Poznań were tested. The tests included an annual training macrocycle, and its individual stages resulted from the time structure of the sports training. In order to assess the level of exercise capacities of the players, a field exercise test of increasing intensity was carried out on a soccer pitch. The test made it possible to determine the 4 millimolar lactate threshold (T LA 4 mmol · l^-1) on the basis of the lactate concentration in blood [LA], to establish the threshold running speed and the threshold heart rate [HR]. The threshold running speed at the level of the 4 millimolar lactate threshold was established using the two-point form of the equation of a straight line. The obtained indicators of the threshold running speed allowed for precise establishment of effort intensity used in individual training in developing aerobic endurance. In order to test the significance of differences in mean values between four dates of tests, a non-parametric Friedman ANOVA test was used. The significance of differences between consecutive dates of tests was determined using a post-hoc Friedman ANOVA test. The tests showed significant differences in values of selected indicators determined at the anaerobic threshold in various stages of an annual training cycle of young soccer players. The most beneficial changes in terms of the threshold running speed were noted on the fourth date of tests, when the participants had the highest values of 4.01 m · s^-1 for older juniors, and 3.80 m · s^-1 for younger juniors. This may be indicative of effective application of an individualized programme of training loads and of good preparation of teams for competition in terms of players’ aerobic endurance.

Efeito da intensidade do exercício de corrida intermitente 30s:15s no tempo de manutenção no ou próximo do VO2max

O presente estudo comparou o tempo mantido acima de 90% (t90VO2max) e de 95% VO2max (t95VO2max) em três diferentes intensidades de exercício. Após a realização de um teste incremental para determinar o VO2max, oito estudantes de educação física ativos (23 ± 3 anos) executaram três sessões de exercícios intermitentes (100, 110 e 120% da velocidade do VO2max (vVO2max)) com razão esforço:recuperação de 30s:15s. O t95VO2max foi significantemente maior em 110%vVO2max (EI110%) (218,1 ± 81,6 s) quando comparado a 100%vVO2max (EI100%) (91,9 ± 75,2s) e a 120%vVO2max (EI120%) (126,3 ± 29,4 s), porém sem diferença entre EI100% e EI120%. O t90VO2max somente apresentou diferença significante entre EI110% e EI120%. Portanto, conclui-se que durante exercício intermitente com razão 30s:15s, a intensidade de 110%vVO2max apresenta-se mais adequada para manter o VO2 próximo ou no VO2max por um tempo maior.

Fast-start strategy increases the time spent above 95 %VO2max during severe-intensity intermittent running exercise

This study aimed to use the intermittent critical velocity (ICV) model to individualize intermittent exercise and analyze whether a fast-start strategy could increase the time spent at or above 95 %VO(2max) (t95VO(2max)) during intermittent exercise. After an incremental test, seven active male subjects performed three intermittent exercise tests until exhaustion at 100, 110, and 120 % of the maximal aerobic velocity to determine ICV. On three occasions, the subjects performed an intermittent exercise test until exhaustion at 105 % (IE105) and 125 % (IE125) of ICV, and at a speed that was initially set at 125 %ICV but which then decreased to 105 %ICV (IE125-105). The intermittent exercise consisted of repeated 30-s runs alternated with 15-s passive rest intervals. There was no difference between the predicted and actual Tlim for IE125 (300 ± 72 s and 284 ± 76 s) and IE105 (1,438 ± 423 s and 1,439 ± 518 s), but for IE125-105 the predicted Tlim underestimated the actual Tlim (888 ± 211 s and 1,051 ± 153 s, respectively). The t95VO(2max) during IE125-105 (289 ± 150 s) was significantly higher than IE125 (113 ± 40 s) and IE105 (106 ± 71 s), but no significant differences were found between IE125 and IE105. It can be concluded that predicting Tlim from the ICV model was affected by the fast-start protocol during intermittent exercise. Furthermore, fast-start protocol was able to increase the time spent at or above 95 %VO2max during intermittent exercise above ICV despite a longer total exercise time at IE105.

Similarity in physiological and perceived exertion responses to exercise at continuous and intermittent critical power

The purpose of this study was to compare the physiological responses [oxygen uptake (VO(2)), heart rate (HR) and blood lactate concentrations ([BLa])] and the rating of perceived exertion (RPE) response until exhaustion (TTE) at the continuous (CP(c)) and intermittent (CP(i)) critical power workloads. Ten moderately active men (25.5 ± 4.2 years, 74.1 ± 8.0 kg, 177.6 ± 4.9 cm) participated in this study. The incremental test was applied to determine the highest values of oxygen uptake (VO(2max)), heart rate (HR(max)), blood lactate concentrations ([BLa(max)]), and maximal aerobic power (MAP). Continuous and intermittent exhaustive predictive trials were performed randomly. The hyperbolic relation between power and time was used to estimate CP(c) and CP(i). CP(i) was derived from predictive trial results at an effort and recovery ratio of 30:30 s. Exercise at CP(c) and CP(i) as well as the physiological and RPE responses were measured until exhaustion. The values of physiological variables during CP(c) and CP(i) did not differ in either TTE test and were lower than the VO(2max), HR(max) and [BLa(max)] values. RPE was maximal at the end of exercise at CP(c) and CP(i). There was a high correlation between VO(2max) (L min(-1)) and CP(c) and CP(i) intensities (r ≥ 0.90) and between MAP, CP(c) and CP(i) (r ≥ 0.95). Similar physiological and RPE responses were found at CP(c) and CP(i) for the times analyzed.

Physiologic effects of directional changes in intermittent exercise in soccer players

The aim of the present study was to compare the physiologic impact of intermittent exercise in specific shuttle running (IS), which requires 180° directional changes, and traditional in-line (IL) running. Ten elite male adult soccer players performed different intermittent exercises according to their maximal aerobic velocity (ν&OV0312;O2max): 30-30 seconds at 100% (30 s of runs at 100% of ν&OV0312;O2max alternated with 30-s recovery period), 105%, and 110% of ν&OV0312;O2max with active recovery, 15-15 seconds at 105%, 110%, and 115% of ν&OV0312;O2max, and 10-10 seconds at 110%, 115%, and 120% of ν&OV0312;O2max with passive recovery. Each exercise was performed in the IL and IS format in a randomized order. Heart rate (HR) expressed in percentage of HR reserve (HRres), postexercise blood lactate concentration [La], and ratings of perceived exertion (RPE) were recorded. The different 30-30 seconds showed significantly higher HRres responses in IS compared with IL (p < 0.01). The [La] and RPE results indicated higher values in IS. In conclusion, the physiologic impact of specific IS is substantially higher than in traditional IL. The changes of direction induce an increase in the anaerobic metabolism solicitation and consequently create different responses compared with traditional IL running. This information can aid coaches in the design of intermittent training programs using classical (IL) or a specific form (IS) of running to induce different physiologic responses.

Aerobic potential, stroke parameters, and coordination in swimming front-crawl performance

The purposes of this review were (1) to review the recent studies conducted in swimming on the assessment of aerobic potential and establishment of exercise-intensity domains (it is important that exercise-intensity domains be accurately defined and their physiological underpinnings well understood to optimize and evaluate training programs); (2) to analyze changes in traditionally measured stroke rate and stroke length during exhaustive swims, particularly in relation to the predetermined intensity domains (introduction of an "optimal swimming technique speed"); and (3) to introduce the latest swimming research on arm coordination that might help us better understand the technical adaptations of swimmers under physical stress.

Influence of recovery intensity on time spent at maximal oxygen uptake during an intermittent session in young, endurance-trained athletes

In this study, we examined the effects of three recovery intensities on time spent at a high percentage of maximal oxygen uptake (t90[Vdot]O(2max)) during a short intermittent session. Eight endurance-trained male adolescents (16 +/- 1 years) performed four field tests until exhaustion: a graded test to determine maximal oxygen uptake ([Vdot]O(2max); 57.4 +/- 6.1 ml x min(-1) . kg(-1)) and maximal aerobic velocity (17.9 +/- 0.4 km x h(-1)), and three intermittent exercises consisting of repeat 30-s runs at 105% of maximal aerobic velocity alternating with 30 s active recovery at 50% (IE(50)), 67% (IE(67)), and 84% (IE(84)) of maximal aerobic velocity. In absolute values, mean t90[Vdot]O(2max) was not significantly different between IE(50) and IE(67), but both values were significantly longer compared with IE(84). When expressed in relative values (as a percentage of time to exhaustion), mean t90[Vdot]O(2max) was significantly higher during IE(67) than during IE(50). Our results show that both 50% and 67% of maximal aerobic velocity of active recovery induced extensive solicitation of the cardiorespiratory system. Our results suggest that the choice of recovery intensity depends on the exercise objective.

Modeling and analysis of the effect of training on V O2 kinetics and anaerobic capacity

In this paper, we present an application of a number of tools and concepts for modeling and analyzing raw, unaveraged, and unedited breath-by-breath oxygen uptake data. A method for calculating anaerobic capacity is used together with a model, in the form of a set of coupled nonlinear ordinary differential equations to make predictions of the VO(2) kinetics, the time to achieve a percentage of a certain constant oxygen demand, and the time limit to exhaustion at intensities other than those in which we have data. Speeded oxygen kinetics and increased time limit to exhaustion are also investigated using the eigenvalues of the fixed points of our model. We also use a way of analyzing the oxygen uptake kinetics using a plot of V O(2)(t) vs V O(2)(t) which allows one to observe both the fixed point solutions and also the presence of speeded oxygen kinetics following training. A method of plotting the eigenvalue versus oxygen demand is also used which allows one to observe where the maximum amplitude of the so-called slow component will be and also how training has changed the oxygen uptake kinetics by changing the strength of the attracting fixed point for a particular demand.

The limits of human performance

Human performance, defined by mechanical resistance and distance per time, includes human, task and environmental factors, all interrelated. It requires metabolic energy provided by anaerobic and aerobic metabolic energy sources. These sources have specific limitations in the capacity and rate to provide re-phosphorylation energy, which determines individual ratios of aerobic and anaerobic metabolic power and their sustainability. In healthy athletes, limits to provide and utilize metabolic energy are multifactorial, carefully matched and include a safety margin imposed in order to protect the integrity of the human organism under maximal effort. Perception of afferent input associated with effort leads to conscious or unconscious decisions to modulate or terminate performance; however, the underlying mechanisms of cerebral control are not fully understood. The idea to move borders of performance with the help of biochemicals is two millennia old. Biochemical findings resulted in highly effective substances widely used to increase performance in daily life, during preparation for sport events and during competition, but many of them must be considered as doping and therefore illegal. Supplements and food have ergogenic potential; however, numerous concepts are controversially discussed with respect to legality and particularly evidence in terms of usefulness and risks. The effect of evidence-based nutritional strategies on adaptations in terms of gene and protein expression that occur in skeletal muscle during and after exercise training sessions is widely unknown. Biochemical research is essential for better understanding of the basic mechanisms causing fatigue and the regulation of the dynamic adaptation to physical and mental training.

Influence of exercise intensity on time spent at high percentage of maximal oxygen uptake during an intermittent session in young endurance-trained athletes

The purpose of this study was to compare, during a 30s intermittent exercise (IE), the effects of exercise intensity on time spent above 90% VO2max(t90VO2max) and time spent above 95% VO2max(t95VO2max) in young endurance trained athletes. We hypothesized that during a 30sIE, an increase in exercise intensity would allow an increase in t90VO2max and t95VO2max due to a decrease in time to achieve 90% or 95% of VO2max. Nine endurance-trained male adolescents took part in three field tests. After determination of their VO2max and maximal aerobic velocity (MAV), they performed, until exhaustion, two intermittent exercise sessions alternating 30s at 100% of MAV (IE(100)) or 110% of MAV (IE(110)) and 30s at 50% of MAV. Mean time to exhaustion (t (lim)) values obtained during IE(100) were significantly longer than during IE(110) (p < 0.01). Moreover, no significant difference was found in t90VO2max or t95VO2max) expressed in absolute or relative (%t (lim)) values between IE(100) and IE(110). In conclusion, an increased of 10% of exercise intensity during a 30s intermittent exercise model (with active recovery), does not seem to be the most efficient exercise to solicit oxygen uptake to its highest level in young endurance-trained athletes.

Manipulating high-intensity interval training: Effects on , the lactate threshold and 3000m running performance in moderately trained males

The aim of this study was to compare the effects of two high-intensity interval training (HIT) programmes on maximal oxygen uptake (.VO(2max)), the lactate threshold (LT) and 3000 m running performance in moderately trained male runners. .VO(2max), the running speed associated with .VO(2max) (V.VO(2max)), the time for which V.VO(2max) can be maintained (T(max)), the running speed at LT (v(LT)) and 3000 m running time (3000 mTT) were determined before and following three different training programmes performed for 10 weeks. Following the pre-test, 17 moderately trained male runners (V O(2max)=51.6+/-2.7ml kg(-1)min(-1)) were divided into training groups based on their 3000 mTT (Group 1, G(1), N=6, 8 x 60% of T(max) at V.VO(2max), 1:1 work:recovery ratio; Group 2, G(2), N=6, 12 x 30s at 130% V.VO(2max), 4.5 min recovery; control group, G(CON), N=5, 60 min at 75% V.VO(2max)). G(1) and G(2) performed two HIT sessions and two 60 min recovery run sessions (75% V.VO(2max)) each week. Control subjects performed four 60 min recovery run sessions (75% V.VO(2max)) each week. In G(1), significant improvements (p<0.05) following HIT were found in .VO(2max) (+9.1%), V.VO(2max) (+6.4%), T(max) (5%), v(LT) (+11.7%) and 3000 mTT (-7.3%). In G(2), significant improvements (p<0.05) following HIT were found in .VO(2max) (+6.2%), V.VO(2max)(+7.8%), T(max) (+32%) and 3000 mTT (-3.4%), but not in v(LT) (+4.7%; p=0.07). No significant changes in these variables were found in G(CON). The present study has shown that 3000 m running performance, .VO(2max), V.VO(2max), T(max) and v(LT) can be significantly enhanced using different HIT programmes in moderately trained runners, but that changes in performance and physiological variables may be more profound using prolonged HIT at intensities of V.VO(2max) with interval durations of 60% T(max).

Índices fisiológicos associados com a "performance" aeróbia em corredores de "endurance": efeitos da duração da prova

O objetivo deste estudo foi analisar a validade do consumo máximo de oxigênio (VO2max), da velocidade correspondente ao VO2max (vVO2max), do tempo de exaustão na vVO2max (Tlim), da economia de corrida (EC) e do limiar anaeróbio (LAn) para a predição da performance de atletas de endurance. Quatorze corredores de endurance (33,4 ± 4,4 anos; 62,7 ± 4,3kg; 166,1 ± 5,0cm; VO2max = 60,4 ± 5,9ml.kg-1.min-1) realizaram os seguintes testes: a) competição simulada nas distâncias de 1.500 e 5.000m. e; b) testes de laboratório para a determinação do VO2max, vVO2max, EC, LAn e Tlim na intensidades de 100% vVO2max. As velocidades (km/h) da vVO2max (18,7 ± 0,8), LAn (17,3 ± 1,1) v1.500m (19,9 ± 0,8) e v5.000m (17,9 ± 0,9) foram significantemente diferentes. A regressão múltipla stepwise revelou que o LAn foi o único preditor da performance da v5.000m, explicando 50% da variação desta performance. Para a v1.500m, o Tlim e a vVO2max explicaram 88% da variação da performance. Com base em nossos resultados, pode-se concluir que a validade dos índices fisiológicos (VO2max, vVO2max, Tlim, EC e LAn), para a predição da performance aeróbia de atletas de endurance, é dependente da distância da prova (1.500 x 5.000m) analisada.

[Oxygen uptake and maximal oxygen uptake: interests and limits of their measurements]

The paper presents a review of the interests and limits of oxygen uptake measurement in the functional testing of athletes and disabled people. The validity of the oxygen uptake as an estimation of the oxygen consumption and aerobic synthesis of ATP is discussed in the introduction of the review. The author discusses the interests of oxygen uptake measurements for the study of energy cost in addition to maximal oxygen uptake. The limits of the study of oxygen uptake kinetics at the beginning of exercise are discussed. The methodology of oxygen measurement is mainly focused on the characteristics of the different ergometers and the choice of an exercise protocol. The review ends with short statements related to the current knowledge on maximal oxygen uptake, its limiting factors and the effects of age, gender, body mass, active muscle mass and training.

Effects of active recovery between series on performance during an intermittent exercise model in young endurance athletes

The purpose of our study was to compare time to exhaustion ( t(lim)) and time spent at a high level of oxygen uptake (V(.)O(2)) during two high-intensity short intermittent exercises (30 s-30 s) realized with or without series. Eleven young endurance-trained athletes [16.6 (0.4) years] took part in three field tests until exhaustion: (1) a maximal graded test to measure their maximal aerobic velocity (MAV) and maximal oxygen uptake (V(.)O(2max)); (2) and (3) two randomized intermittent exercises (30 s at 110% of MAV alternated with 30 s at 50% of MAV): one alternating repetitions non-stop (IE) and another including 4 min recovery every six repetitions (IEs). The mean t(lim) measured during IEs was significantly longer than IE [respectively 960.0 (102.0) s vs 621.8 (56.2) s]. The time spent at V(.)O(2max)( t(V(.)O2max)) and the time spent above 90% of V(.)O(2max)( t(90%V(.)O2max)) did not differ significantly according to the type of exercise: with or without series [respectively t(V(.)O2max) was 158.2 (59.7) s vs 178.0 (56.5) s and t(90%<Vdot>O2max) was 290.4 (84.3) s vs 345.0 (61.6) s] but when expressed as a relative value, t(90%<Vdot>O2max) during IEs was significantly lower than during IE [respectively 36.4 (10.4)% t(lim) vs 58.3 (8.7)% t(lim)]. Despite a significant decrease ( P<0.005) of time to achieve 90% of V(.)O(2max) at the start of each series during IEs [respectively 165.0 (43.1) s for the first series and 82.5 (15.8) s for the second series ( n=6)] the time spent under 90% of V(.)O(2max) limited the t(90%V(.)O2max) during each series. In conclusion, our results showed that intermittent exercise with series does not permit an increase in the time spent at a high level of V(.)O(2); however, the athletes performed more repetitions of short intense exercise.

[Effect of 4 weeks of training on the limit time at VO2 max]

The purpose of this study was to examine the effect of 4 weeks training in running on the time spent at VO2max (tlim VO2max). Eight athletes carried out, before and after an aerobic training, an incremental and five exhaustive tests at 90, 95, 100, 115% vVO2max and at the critical power at VO2max (CV'; slope of the linear relation between the tlim VO2max and the distance limit at VO2max). This training did not significantly improve VO2max (p = 0.17) or tlim VO2max (p = 0.72). However, the "tlim VO2max-intensity" curve was shifted toward the right, meaning that the athlete had to run at a higher intensity after training to obtain the same tlim VO2max. Tlim VO2max at CV' before training was significantly higher than tlim VO2max at 90, 95, 100, and 115% vVO2max (p < 0.05). This training increased CV' in absolute value (13.9 +/- 1.3 vs. 14.9 +/- 1.2 km.h-1, p < 0.05; n = 6) but not in relative value (86 +/- 4 vs. 86 +/- 5% vVO2max; p = 0.9). In conclusion, in spite of the shift of the "tlim VO2max-intensity" curve, tlim VO2max was not significantly increased by this training. Furthermore, CV' allowed subjects to spend the longest time of exercise at VO2max during a continuous exercise with constant speed, but CV', expressed in % vVO2max, did not improve with this training.