Facteurs Limitants de la Performance en Triathlon

Triathlon is a multievent sport (swimming, cycling, running). Long duration triathlons can induce physiological stress that can be modulated by environmental conditions. Certain factors promote performance, others limit it. A minimal level of maximal oxygen uptake is required, but it does not always determine the performance. For triathletes, the low hematocrit values do not reflect anemia and therefore do not limit performance. The appearance of clinical signs of dehydratation and of digestive impairment may limit performance. The performance in swimming does not play the most important role in triathlon performance, but the physiological conditions in which the first transition is made can limit performance in the two following events; this is also the case for the second transition. Triathlon races cause muscle damage whose signs persist several days. Given the hormonal responses and the indices of muscle damage, it appears necessary to rest at least 5 days to avoid overtraining. It is difficult to define precisely how much one should train for each of the three events. However, it can be concluded that triathlon training has to be taken as a whole. Key words: training, endurance, recovery, triathlete

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Decreases in maximal oxygen uptake following long-duration spaceflight: Role of convective and diffusive O2 transport mechanisms

Journal of Applied Physiology ◽

10.1152/japplphysiol.00280.2016 ◽

2017 ◽

Vol 122 (4) ◽

pp. 968-975 ◽

Cited By ~ 9

Author(s):

C. J. Ade ◽

R. M. Broxterman ◽

A. D. Moore ◽

T. J. Barstow

Keyword(s):

Oxygen Uptake ◽

International Space Station ◽

Maximal Oxygen Uptake ◽

Linear Regression Analysis ◽

Space Station ◽

Hemoglobin Concentration ◽

Integrative Approach ◽

Transport Pathway ◽

International Space ◽

Long Duration

We have previously predicted that the decrease in maximal oxygen uptake (V̇o2max) that accompanies time in microgravity reflects decrements in both convective and diffusive O2 transport to the mitochondria of the contracting myocytes. The aim of this investigation was therefore to quantify the relative changes in convective O2 transport (Q̇o2) and O2 diffusing capacity (Do2) following long-duration spaceflight. In nine astronauts, resting hemoglobin concentration ([Hb]), V̇o2max, maximal cardiac output (Q̇Tmax), and differences in arterial and venous O2 contents ([Formula: see text]-[Formula: see text]) were obtained retrospectively for International Space Station Increments 19–33 (April 2009–November 2012). Q̇o2 and Do2 were calculated from these variables via integration of Fick’s Principle of Mass Conservation and Fick’s Law of Diffusion. V̇o2max significantly decreased from pre- to postflight (−53.9 ± 45.5%, P = 0.008). The significant decrease in Q̇Tmax (−7.8 ± 9.1%, P = 0.05), despite an unchanged [Hb], resulted in a significantly decreased Q̇o2 (−11.4 ± 10.5%, P = 0.02). Do2 significantly decreased from pre- to postflight by −27.5 ± 24.5% ( P = 0.04), as did the peak [Formula: see text]-[Formula: see text] (−9.2 ± 7.5%, P = 0.007). With the use of linear regression analysis, changes in V̇o2max were significantly correlated with changes in Do2 ( R2 = 0.47; P = 0.04). These data suggest that spaceflight decreases both convective and diffusive O2 transport. These results have practical implications for future long-duration space missions and highlight the need to resolve the specific mechanisms underlying these spaceflight-induced changes along the O2 transport pathway. NEW & NOTEWORTHY Long-duration spaceflight elicited a significant decrease in maximal oxygen uptake. Given the adverse physiological adaptations to microgravity along the O2 transport pathway that have been reported, an integrative approach to the determinants of postflight maximal oxygen uptake is needed. We demonstrate that both convective and diffusive oxygen transport are decreased following ~6 mo International Space Station missions.

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Exercise cardiorespiratory and thermoregulatory responses in normoxic, hypoxic, and hot environment following 10-day continuous hypoxic exposure

Journal of Applied Physiology ◽

10.1152/japplphysiol.01114.2017 ◽

2018 ◽

Vol 125 (4) ◽

pp. 1284-1295 ◽

Cited By ~ 4

Author(s):

Alexandros Sotiridis ◽

Tadej Debevec ◽

Adam C. McDonnell ◽

Urša Ciuha ◽

Ola Eiken ◽

...

Keyword(s):

Exercise Training ◽

Oxygen Uptake ◽

Environmental Conditions ◽

Maximal Oxygen Uptake ◽

Moderate Intensity ◽

Peak Power Output ◽

Hypoxic Exposure ◽

Moderate Intensity Exercise ◽

Thermoregulatory Responses ◽

Before And After

We examined the effects of acclimatization to normobaric hypoxia on aerobic performance and exercise thermoregulatory responses under normoxic, hypoxic, and hot conditions. Twelve men performed tests of maximal oxygen uptake (V̇O2max) in normoxic (NOR), hypoxic [HYP; 13.5% fraction of inspired oxygen (FiO2)], and hot (HE; 35°C, 50% relative humidity) conditions in a randomized manner before and after a 10-day continuous normobaric hypoxic exposure [FiO2 = 13.65 (0.35)%, inspired partial pressure of oxygen = 87 (3) mmHg]. The acclimatization protocol included daily exercise [60 min at 50% hypoxia-specific peak power output (Wpeak)]. All maximal tests were preceded by a steady-state exercise (30 min at 40% Wpeak) to assess the sweating response. Hematological data were assessed from venous blood samples obtained before and after acclimatization. V̇o2max increased by 10.7% ( P = 0.002) and 7.9% ( P = 0.03) from pre-acclimatization to post acclimatization in NOR and HE, respectively, whereas no differences were found in HYP [pre: 39.9 (3.8) vs. post: 39.4 (5.1) ml·kg−1·min−1, P = 1.0]. However, the increase in V̇O2max did not translate into increased Wpeak in either NOR or HE. Maximal heart rate and ventilation remained unchanged following acclimatization. Νo differences were noted in the sweating gain and thresholds independent of the acclimatization or environmental conditions. Hypoxic acclimatization markedly increased hemoglobin ( P < 0.001), hematocrit ( P < 0.001), and extracellular HSP72 ( P = 0.01). These data suggest that 10 days of normobaric hypoxic acclimatization combined with moderate-intensity exercise training improves V̇o2max in NOR and HE, but does not seem to affect exercise performance or thermoregulatory responses in any of the tested environmental conditions. NEW & NOTEWORTHY The potential crossover effect of hypoxic acclimatization on performance in the heat remains unexplored. Here we show that 10-day continuous hypoxic acclimatization combined with moderate-intensity exercise training can increase maximal oxygen uptake in hot conditions.

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Determining Validity of Critical Power Estimated Using a Three-Minute All-Out Test in Hot Environments

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph18179193 ◽

2021 ◽

Vol 18 (17) ◽

pp. 9193

Author(s):

Yu-Hsuan Kuo ◽

Ching-Feng Cheng ◽

Yu-Chi Kuo

Keyword(s):

High Temperature ◽

Oxygen Uptake ◽

Exercise Performance ◽

Power Output ◽

Maximal Oxygen Uptake ◽

Critical Power ◽

Physiological Stress ◽

Exercise Tests ◽

Test Power ◽

Hot Environments

The aim of this study was to investigate the effects of heat on the validity of end-test power (EP) derived from a 3-min all-out test (3MT), which is considered as an alternative method for determining the conventional critical power. Twelve male cyclists were required to perform incremental exercise tests (IET) and 3MTs in both high temperature (HT; 35 °C) and thermoneutral temperature (NT; 22 °C) environments. Maximal oxygen uptake (VO2max), and first and second ventilatory thresholds (VT1 and VT2, respectively) against the power output (wVO2max, wVT1, and wVT2) were measured during IETs. EP was recorded during the 3MTs. A significant correlation was observed between wVT2 and EP under NT (r = 0.674, p < 0.05) and under HT (r = 0.672, p < 0.05). However, wVO2max, wVT1, wVT2, and EP were significantly higher in NT than in HT (p < 0.05). In conclusion, although the physiological stress induced by HT might impair exercise performance, the EP derived from 3MT can validly estimate wVT2 under HT conditions.

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Predicting the 2000‐m Rowing Ergometer Performance from Anthropometric, Maximal Oxygen Uptake and 60‐s Mean Power Variables in National Level Young Rowers

Journal of Human Kinetics ◽

10.2478/hukin-2020-0038 ◽

2020 ◽

Vol 75 (1) ◽

pp. 77-83

Author(s):

Dario Cerasola ◽

Marianna Bellafiore ◽

Angelo Cataldo ◽

Daniele Zangla ◽

Antonino Bianco ◽

...

Keyword(s):

Oxygen Uptake ◽

Body Mass ◽

Maximal Oxygen Uptake ◽

National Level ◽

Body Height ◽

Mean Power ◽

Long Duration ◽

Rowing Performance ◽

Rowing Ergometer ◽

Fast Start

Abstract Many studies reported various relationships between 2000-m rowing performance and anthropometric as well as metabolic variables, however, little is known about 60-s mean power in elite youth athletes. The aim of this study was to develop different regression models to predict 2000-m rowing indoor performance time (t2000) using anthropometric variables, maximal oxygen uptake (VO2max) and mean power established during a 60-s all-out test (W60) in national elite youth rowers. Fifteen youth male Italian rowers (age: 15.7 ± 2.0 years; body height: 176.0 ± 8.0 cm; body mass: 71.2 ± 10.0 kg) performed an incremental maximal test, a 60-s all-out test and a 2000-m race simulation using a Concept2 rowing ergometer to assess VO2max, W60 and t2000, respectively. The relationships of all variables with t2000 were investigated through Pearson’s correlation. Multiple regression analyses were used to verify the best prediction model of 2000-m indoor rowing performance. The reliability of these models was expressed by R2 and the standard error of estimate. The results showed that t2000 was significantly correlated with all the examined variables, except for VO2max/body mass and age, and exhibited the significantly highest relationship with W60 (r = -0.943). The combination of anthropometric, VO2max and W60 variables was found to be the most reliable equation to predict t2000 (R2 = 0.94, SEE = 6.4). W60 measure should be considered when monitoring the rower’s capability to perform high-intensity phases, important during the race’s fast start and end. Not requiring expensive equipment and long duration, a 60-s all-out test could be considered a valuable tool for predicting 2000-m performance of elite youth rowers.

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Comparison of Environmental Conditions on Summits of Mount Everest and K2 in Climbing and Midwinter Seasons

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph18063040 ◽

2021 ◽

Vol 18 (6) ◽

pp. 3040

Author(s):

Robert K. Szymczak ◽

Michał K. Pyka ◽

Tomasz Grzywacz ◽

Michał Marosz ◽

Marta Naczyk ◽

...

Keyword(s):

Wind Speed ◽

Oxygen Uptake ◽

Environmental Conditions ◽

Maximal Oxygen Uptake ◽

Barometric Pressure ◽

Extreme Conditions ◽

Equivalent Temperature ◽

Mount Everest ◽

Wind Chill ◽

Vertical Climbing

(1) Background: Today’s elite alpinists target K2 and Everest in midwinter. This study aimed to asses and compare weather at the summits of both peaks in the climbing season (Everest, May; K2, July) and the midwinter season (January and February). (2) Methods: We assessed environmental conditions using the ERA5 dataset (1979–2019). Analyses examined barometric pressure (BP), temperature (Temp), wind speed (Wind), perceived altitude (Alt), maximal oxygen uptake (VO2max), vertical climbing speed (Speed), wind chill equivalent temperature (WCT), and facial frostbite time (FFT). (3) Results: Most climbing-season parameters were found to be more severe (p < 0.05) on Everest than on K2: BP (333 ± 1 vs. 347 ± 1 hPa), Alt (8925 ± 20 vs. 8640 ± 20 m), VO2max (16.2 ± 0.1 vs. 17.8 ± 0.1 ml·kg−1·min−1), Speed (190 ± 2 vs. 223 ± 2 m·h−1), Temp (−26 ± 1 vs. −21 ± 1°C), WCT (−45 ± 2 vs. −37 ± 2 °C), and FFT (6 ± 1 vs. 11 ± 2 min). Wind was found to be similar (16 ± 3 vs. 15 ± 3 m·s−1). Most midwinter parameters were found to be worse (p < 0.05) on Everest vs. K2: BP (324 ± 2 vs. 326 ± 2 hPa), Alt (9134 ± 40 vs. 9095 ± 48 m), VO2max (15.1 ± 0.2 vs. 15.3 ± 0.3 ml·kg−1·min−1), Speed (165 ± 5 vs. 170 ± 6 m·h−1), Wind (41 ± 6 vs. 27 ± 4 m·s−1), and FFT (<1 min vs. 1 min). Everest’s Temp of −36 ± 2 °C and WCT −66 ± 3 °C were found to be less extreme than K2’s Temp of −45 ± 1 °C and WCT −76 ± 2 °C. (4) Conclusions: Everest presents more extreme conditions in the climbing and midwinter seasons than K2. K2’s 8° higher latitude makes its midwinter BP similar and Temp lower than Everest’s. K2’s midwinter conditions are more severe than Everest’s in the climbing season.

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