Format

Send to

Choose Destination
Eur J Appl Physiol. 2019 Sep 25. doi: 10.1007/s00421-019-04215-5. [Epub ahead of print]

No ergogenic effects of a 10-day combined heat and hypoxic acclimation on aerobic performance in normoxic thermoneutral or hot conditions.

Author information

1
Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Jamova 39, SI-1000, Ljubljana, Slovenia.
2
Jozef Stefan International Postgraduate School, Ljubljana, Slovenia.
3
Section of Sport Medicine and Biology of Exercise, School of Physical Education and Sport Science, National and Kapodistrian University of Athens, Athens, Greece.
4
Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Jamova 39, SI-1000, Ljubljana, Slovenia. igor.mekjavic@ijs.si.

Abstract

PURPOSE:

Hypoxic acclimation enhances convective oxygen delivery to the muscles. Heat acclimation-elicited thermoregulatory benefits have been suggested not to be negated by adding daily exposure to hypoxia. Whether concomitant acclimation to both heat and hypoxia offers a synergistic enhancement of aerobic performance in thermoneutral or hot conditions remains unresolved.

METHODS:

Eight young males ([Formula: see text]: 51.6 ± 4.6 mL min-1 kg-1) underwent a 10-day normobaric hypoxic confinement (FiO2 = 0.14) interspersed with daily 90-min normoxic controlled hyperthermia (target rectal temperature: 38.5 °C) exercise sessions. Prior to, and following the confinement, the participants conducted a 30-min steady-state exercise followed by incremental exercise to exhaustion on a cycle ergometer in thermoneutral normoxic (NOR), thermoneutral hypoxic (FiO2 = 0.14; HYP) and hot (35 °C, 50% relative humidity; HE) conditions in a randomized and counterbalanced order. The steady-state exercise was performed at 40% NOR peak power output (Wpeak) to evaluate thermoregulatory function. Blood samples were obtained from an antecubital vein before, on days 1 and 10, and the first day post-acclimation.

RESULTS:

[Formula: see text] and ventilatory thresholds were not modified in any environment following acclimation. Wpeak increased by 6.3 ± 3.4% in NOR and 4.0 ± 4.9% in HE, respectively. The magnitude and gain of the forehead sweating response were augmented in HE post-acclimation. EPO increased from baseline (17.8 ± 7.0 mIU mL-1) by 10.7 ± 8.8 mIU mL-1 on day 1 but returned to baseline levels by day 10 (15.7 ± 5.9 mIU mL-1).

DISCUSSION:

A 10-day combined heat and hypoxic acclimation conferred only minor benefits in aerobic performance and thermoregulation in thermoneutral or hot conditions. Thus, adoption of such a protocol does not seem warranted.

KEYWORDS:

Aerobic performance; Heat acclimation; Hypoxic acclimation; Thermoregulation

PMID:
31555926
DOI:
10.1007/s00421-019-04215-5

Supplemental Content

Full text links

Icon for Springer
Loading ...
Support Center