In:
Sports Medicine, Springer Science and Business Media LLC, Vol. 51, No. 7 ( 2021-07), p. 1509-1525
Abstract:
Heat acclimation and acclimatisation (HA) is typically used to enhance tolerance to the heat, thereby improving performance. HA might also confer a positive adaptation to maximal oxygen consumption ( $$V{\text{O}}_{2\max }$$ V O 2 max ), although this has been historically debated and requires clarification via meta-analysis. Objectives (1) To meta-analyse all studies (with and without control groups) that have investigated the effect of HA on $$V{\text{O}}_{2\max }$$ V O 2 max adaptation in thermoneutral or hot environments; (2) Conduct meta-regressions to establish the moderating effect of selected variables on $$V{\text{O}}_{2\max }$$ V O 2 max adaptation following HA. Methods A search was performed using various databases in May 2020. The studies were screened using search criteria for eligibility. Twenty-eight peer-reviewed articles were identified for inclusion across four separate meta-analyses: (1) Thermoneutral $$V{\text{O}}_{2\max }$$ V O 2 max within-participants (pre-to-post HA); (2) Hot $$V{\text{O}}_{2\max }$$ V O 2 max within-participants (pre-to-post HA); (3) Thermoneutral $$V{\text{O}}_{2\max }$$ V O 2 max measurement; HA vs . control groups; (4) Hot $$V{\text{O}}_{2\max }$$ V O 2 max measurement, HA vs . control groups. Meta-regressions were performed for each meta-analysis based on: isothermal vs . iso-intensity programmes, days of heat exposure, HA ambient temperature (°C), heat index, HA session duration (min), ambient thermal load (HA session x ambient temperature), mean mechanical intensity (W) and the post-HA testing period (days). Results The meta-analysis of pre–post differences in thermoneutral $$V{\text{O}}_{2\max }$$ V O 2 max demonstrated small-to-moderate improvements in $$V{\text{O}}_{2\max }$$ V O 2 max (Hedges’ g = 0.42, 95% CI 0.24–0.59, P 〈 0.001), whereas moderate improvements were found for the equivalent analysis of hot $$V{\text{O}}_{2\max }$$ V O 2 max changes (Hedges’ g = 0.63, 95% CI 0.26–1.00, P 〈 0.001), which were positively moderated by the number of days post-testing ( P = 0.033, β = 0.172). Meta-analysis of control vs . HA thermoneutral $$V{\text{O}}_{2\max }$$ V O 2 max demonstrated a small improvement in $$V{\text{O}}_{2\max }$$ V O 2 max in HA compared to control (Hedges’ g = 0.30, 95% CI 0.06–0.54, P = 0.014) and this effect was larger for the equivalent hot $$V{\text{O}}_{2\max }$$ V O 2 max analysis where a higher ( moderate-to-large ) improvement in $$V{\text{O}}_{2\max }$$ V O 2 max was found (Hedges’ g = 0.75, 95% CI 0.22–1.27, P = 0.005), with the number of HA days ( P = 0.018; β = 0.291) and the ambient temperature during HA ( P = 0.003; β = 0.650) positively moderating this effect. Conclusion HA can enhance $$V{\text{O}}_{2\max }$$ V O 2 max adaptation in thermoneutral or hot environments, with or without control group consideration, by at least a small and up to a moderate–large amount, with the larger improvements occurring in the heat. Ambient heat, number of induction days and post-testing days can explain some of the changes in hot $$V{\text{O}}_{2\max }$$ V O 2 max adaptation.
Type of Medium:
Online Resource
ISSN:
0112-1642
,
1179-2035
DOI:
10.1007/s40279-021-01445-6
Language:
English
Publisher:
Springer Science and Business Media LLC
Publication Date:
2021
detail.hit.zdb_id:
2025521-4
SSG:
31
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