Article Title
The Effects of Heat Acclimatization, Heat Acclimation, and Intermittent Heat Training on Maximal Oxygen Uptake
Abstract
Maximal oxygen uptake (VO2max) 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 VO2max responses are unknown. PURPOSE: To determine the effects of HA/HAz and IHT on VO2max in endurance runners and identify how long VO2max 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; VO2max, 57.48 ± 7.03 ml.kg-1.min-1) completed VO2max 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 VO2max and maximal heart rate at VO2max (HRmax) for baseline, pre-HA, post-HA, IHT4, and IHT8 were analyzed using repeated-measures ANOVAs with Bonferroni corrections post-hoc. RESULTS: No significant VO2max 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 VO2max at post-HA, IHT4, and IHT8 (p = 0.67). However, significant HRmax 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 HRmax differences were shown for post-HA, IHT4, and IHT8 (p = 0.59). CONCLUSION: No changes in VO2max were identified among endurance runners following HA/HAz, potentially due to participants’ high aerobic fitness levels. As IHT maintained VO2max following 8 weeks without repeated heat exposure, it is potentially a beneficial strategy to minimize VO2max 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