Temperate performance benefits after heat, but not combined heat and hypoxic training

Independent heat and hypoxic exposure can enhance temperate endurance performance in trained athletes, although their combined effects remain unknown.

This study examined whether the addition of heat interval training during ‘‘live high, train low’’ (LHTL) hypoxic exposure would result in enhanced performance and physiological adaptations as compared with heat or temperate training.

METHODS

Twenty-six well-trained runners completed 3 wk of interval training assigned to one of three conditions: 1) LHTL hypoxic exposure plus heat training (H + H; 3000 m for 13 hIdj1, train at 33 -C, 60% relative humidity [RH]), 2) heat training with no hypoxic exposure (HOT, live at G600 m and train at 33-C, 60% RH), or 3) temperate training with no hypoxic exposure (CONT; live at G600 m and train at 14-C, 55% RH). Performance 3-km time-trials (3-km TT), running economy, hemoglobin mass, and plasma volume were assessed using magnitude-based inferences statistical approach before (Baseline), after (Post), and 3 wk (3wkP) after exposure.

RESULTS

Compared with Baseline, 3-km TT performance was likely increased in HOT at 3wkP (j3.3% T 1.3%; mean T 90% confidence interval), with no performance improvement in either H + H or CONT. Hemoglobin mass increased by 3.8% T 1.8% at Post in H + H only. Plasma volume in HOT was possibly elevated above H + H and CONT at Post but not at 3wkP. Correlations between changes in 3-km TT performance and physiological adaptations were unclear.

LIMITATIONS

Despite the previously mentioned findings, some limitations should be acknowledged. Although participants were blinded to the specific temperature and oxygen concentrations during the study, they were unable to be blinded to their assigned environmental conditions. Furthermore, the heat and hypoxic environmental stimuli in the study were simulated and, therefore, may not be replicated in natural heat or hypoxic environments. Specifically, physiological adaptations resulting from hypobaric hypoxia or simulated normobaric hypoxia are suggested to differ; however, recent evidence suggests no difference in V ˙O2max or 3-km run time-trial. However, we recommend future research to investigate if similar results would occur in athletes living and training a natural environment. Another limitation is that we only investigated 3-km TT running performance benefits in a temperate environment.

CONCLUSION

In summary, 3 week of interval training in a hot environment may enhance 3-km TT performance in a temperate environment in the weeks after exposure. The present results showed that although adding LHTL to heat interval training can elicit a hematological response, these physiological changes do not result in improved 3-km TT performance. Collectively, these findings indicate that combining LHTL with heat exposure does not provide additional benefit over heat training alone, and the incorporation of heat into a training camp may be a simple approach to improving athletic performance. However, factors such as psychology of the athlete, dose of stimuli, environment, and training status should be considered when including heat or hypoxia as part of an athlete’s training program.

KEYWORDS

Heat acclimation, hypoxia, plasma volume, endurance, hemoglobin mass.

ACKNOWLEDGEMENTS

The authors thank the Australian Institute of Sport and Australian Sports Commissions Big Ideas Fund for their financial support as well as the Douglass Hanly Moir for assistance with blood analysis. A special thanks to all staff at the New South Wales Institute of Sport, University of Canberra Research Institute for Sport and Exercise, University of Technology Sydney, and Department of Physiology at the Australian Institute of Sport for their support during the study and assistance during data collection. In particular, the authors thank Chis Gore, Laura Garvican-Lewis, Kevin Thompson, Val Chan, Brad Clark, Leanne Meyers, Graeme Albon, Jamie Plowman, and Sabrina Skorski.

REFERENCE

McCleave, E. L., Slattery, K. M., Duffield, R., Saunders, P. U., Sharma, A. P., Crowcroft, S. J. and Coutts, A. J. Temperate performance benefits after heat, but not combined heat and hypoxic training. Med. Sci. Sports Exerc., Vol. 49, No. 3, pp. 509–517, 2017.