The Effects of Heat Acclimatization, Heat Acclimation, and Intermittent Heat Training on Maximal Oxygen Uptake

Authors

Ryan A. Dunn, Texas Tech UniversityFollow
Lauren A. Fry, University of ConnecticutFollow
Yasuki Sekiguchi, Texas Tech UniversityFollow
Courteney L. Benjamin, Samford UniversityFollow
Ciara N. Manning, University of ConnecticutFollow
Robert A. Huggins, University of ConnecticutFollow
Rebecca L. Stearns, University of ConnecticutFollow
Douglas J. Casa, University of ConnecticutFollow

Abstract

Maximal oxygen uptake (VO_2max) is an important determinant of endurance performance. Heat acclimation/acclimatization (HA/HAz) strategies elicit improvements in endurance performance. When heat exposure is reduced, intermittent heat training (IHT) is potentially beneficial to alleviate HA/HAz adaptation decay, however corresponding VO_2max responses are unknown. PURPOSE: To determine the effects of HA/HAz and IHT on VO_2max in endurance runners and identify how long VO_2max adaptations remain following removal of repeated heat exposure. METHODS: Twenty-seven male endurance runners (mean ± SD; age, 36 ± 12 years; body mass, 73.03 ± 8.97 kg; height, 178.81 ± 6.39 cm; VO_2max, 57.48 ± 7.03 ml.kg^-1.min^-1) completed VO_2max and exercise testing at five time points; baseline, pre-HA, post-HA, week 4 of IHT (IHT₄), and week 8 of IHT (IHT₈). Exercise testing and HA environmental conditions were the same (ambient temperature, 35.42 ± 1.06°C; relative humidity, 46.35 ± 2.48%). Following baseline testing, participants completed HAz, proceeded by 5 days of HA involving exercise to induce hyperthermia (38.50 - 39.50°C) for 60 minutes. Participants were then randomly assigned to one of three IHT groups: once weekly (n = 9), twice weekly (n = 10), or no IHT (n = 8). Differences in VO_2max and maximal heart rate at VO_2max (HR_max) for baseline, pre-HA, post-HA, IHT₄, and IHT₈ were analyzed using repeated-measures ANOVAs with Bonferroni corrections post-hoc. RESULTS: No significant VO_2max differences were observed between baseline (57.92 ± 6.82 ml.kg^-1.min^-1), pre-HA (59.65 ± 8.24 ml.kg^-1.min^-1), and post-HA (59.49 ± 7.18 ml.kg^-1.min^-1, p = 0.36). No significant group or time effects were identified for VO_2max at post-HA, IHT₄, and IHT₈ (p = 0.67). However, significant HR_max differences were observed between baseline (180 ± 11 beats.min^-1), pre-HA (177 ± 10 beats.min^-1), and post-HA tests (175 ± 10 beats.min^-1, p = 0.01). No significant group or time HR_max differences were shown for post-HA, IHT₄, and IHT₈ (p = 0.59). CONCLUSION: No changes in VO2_max were identified among endurance runners following HA/HAz, potentially due to participants’ high aerobic fitness levels. As IHT maintained VO_2max following 8 weeks without repeated heat exposure, it is potentially a beneficial strategy to minimize VO_2max adaptation decay in endurance athletes.

Recommended Citation

Dunn, Ryan A.; Fry, Lauren A.; Sekiguchi, Yasuki; Benjamin, Courteney L.; Manning, Ciara N.; Huggins, Robert A.; Stearns, Rebecca L.; and Casa, Douglas J. (2023) "The Effects of Heat Acclimatization, Heat Acclimation, and Intermittent Heat Training on Maximal Oxygen Uptake," International Journal of Exercise Science: Conference Proceedings: Vol. 2: Iss. 15, Article 16.
Available at: https://digitalcommons.wku.edu/ijesab/vol2/iss15/16