Effects of 10 days of separate heat and hypoxic exposure on heat acclimation and temperate exercise performance

Authors: Rendell, R., Prout, J., Massey, H., Costello, J., Young, J., Tipton, M. and Corbett, J.

http://eprints.bournemouth.ac.uk/33399/

Journal: American Journal of Physiology: Regulatory, Integrative and Comparative Physiology

Publisher: American Physiological Society

ISSN: 0363-6119

This data was imported from PubMed:

Authors: Rendell, R.A., Prout, J., Costello, J.T., Massey, H.C., Tipton, M.J., Young, J.S. and Corbett, J.

http://eprints.bournemouth.ac.uk/33399/

Journal: Am J Physiol Regul Integr Comp Physiol

Volume: 313

Issue: 3

Pages: R191-R201

eISSN: 1522-1490

DOI: 10.1152/ajpregu.00103.2017

Adaptations to heat and hypoxia are typically studied in isolation but are often encountered in combination. Whether the adaptive response to multiple stressors affords the same response as when examined in isolation is unclear. We examined 1) the influence of overnight moderate normobaric hypoxia on the time course and magnitude of adaptation to daily heat exposure and 2) whether heat acclimation (HA) was ergogenic and whether this was influenced by an additional hypoxic stimulus. Eight males [V̇o2max = 58.5 (8.3) ml·kg-1·min-1] undertook two 11-day HA programs (balanced-crossover design), once with overnight normobaric hypoxia (HAHyp): 8 (1) h per night for 10 nights [[Formula: see text] = 0.156; SpO2 = 91 (2)%] and once without (HACon). Days 1, 6, and 11 were exercise-heat stress tests [HST (40°C, 50% relative humidity, RH)]; days 2-5 and 7-10 were isothermal strain [target rectal temperature (Tre) ~38.5°C], exercise-heat sessions. A graded exercise test and 30-min cycle trial were undertaken pre-, post-, and 14 days after HA in temperate normoxia (22°C, 55% RH; FIO2 = 0.209). HA was evident on day 6 (e.g., reduced Tre, mean skin temperature (T̄sk), heart rate, and sweat [Na+], P < 0.05) with additional adaptations on day 11 (further reduced T̄sk and heart rate). HA increased plasma volume [+5.9 (7.3)%] and erythropoietin concentration [+1.8 (2.4) mIU/ml]; total hemoglobin mass was unchanged. Peak power output [+12 (20) W], lactate threshold [+15 (18) W] and work done [+12 (20) kJ] increased following HA. The additional hypoxic stressor did not affect these adaptations. In conclusion, a separate moderate overnight normobaric hypoxic stimulus does not affect the time course or magnitude of HA. Performance may be improved in temperate normoxia following HA, but this is unaffected by an additional hypoxic stressor.

This data was imported from Scopus:

Authors: Rendell, R.A., Prout, J., Costello, J.T., Massey, H.C., Tipton, M.J., Young, J.S. and Corbett, J.

http://eprints.bournemouth.ac.uk/33399/

Journal: American Journal of Physiology - Regulatory Integrative and Comparative Physiology

Volume: 313

Issue: 3

Pages: R191-R201

eISSN: 1522-1490

ISSN: 0363-6119

DOI: 10.1152/ajpregu.00103.2017

© 2017 the American Physiological Society. Adaptations to heat and hypoxia are typically studied in isolation but are often encountered in combination. Whether the adaptive response to multiple stressors affords the same response as when examined in isolation is unclear. We examined 1) the influence of overnight moderate normobaric hypoxia on the time course and magnitude of adaptation to daily heat exposure and 2) whether heat acclimation (HA) was ergogenic and whether this was influenced by an additional hypoxic stimulus. Eight males [VO2max = 58.5 (8.3) ml·kg-1·min-1] undertook two 11-day HA programs (balanced-crossover design), once with overnight normobaric hypoxia (HAHyp): 8 (1) h per night for 10 nights [FIO2 = 0.156; SpO2 = 91 (2)%] and once without (HACon). Days 1, 6, and 11 were exercise-heat stress tests [HST (40°C, 50% relative humidity, RH)]; days 2-5 and 7-10 were isothermal strain [target rectal temperature (Tre) ˜38.5°C], exercise-heat sessions. A graded exercise test and 30-min cycle trial were undertaken pre-, post-, and 14 days after HA in temperate normoxia (22°C, 55% RH; FIO2 = 0.209). HA was evident on day 6 (e.g., reduced Tre, mean skin temperature (Tsk), heart rate, and sweat [Na+], P < 0.05) with additional adaptations on day 11 (further reduced Tsk and heart rate). HA increased plasma volume [+5.9 (7.3)%] and erythropoietin concentration [+1.8 (2.4) mIU/ml]; total hemoglobin mass was unchanged. Peak power output [+12 (20) W], lactate threshold [+15 (18) W] and work done [+12 (20) kJ] increased following HA. The additional hypoxic stressor did not affect these adaptations. In conclusion, a separate moderate overnight normobaric hypoxic stimulus does not affect the time course or magnitude of HA. Performance may be improved in temperate normoxia following HA, but this is unaffected by an additional hypoxic stressor.

This data was imported from Web of Science (Lite):

Authors: Rendell, R.A., Prout, J., Costello, J.T., Massey, H.C., Tipton, M.J., Young, J.S. and Corbett, J.

http://eprints.bournemouth.ac.uk/33399/

Journal: AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY

Volume: 313

Issue: 3

Pages: R191-R201

eISSN: 1522-1490

ISSN: 0363-6119

DOI: 10.1152/ajpregu.00103.2017

The data on this page was last updated at 05:19 on January 20, 2021.