The effect of heat acclimation or acclimatisation on exercise performance and capacity in the heat: preliminary meta-analysis data
© Reeve et al.; 2015
Published: 14 September 2015
Exercise performance and capacity are impaired in hot and humid compared to temperate conditions ,  and so researchers, coaches and athletes are interested in strategies to attenuate this impairment. Heat acclimation (or acclimatisation) (HA) is one approach that may reduce the thermal strain of exercising in hot conditions and benefit exercise performance , . This meta-analysis quantified the magnitude of effect that HA has on exercise performance and capacity in the heat, and tested whether the magnitude of effect is related to the volume or intensity of heat stress experienced.
The PubMed database was searched (09/01/15) using the first-order search terms acclimation, acclimatization, acclimatisation and adaptation and second-order search terms heat, exercise, performance, capacity and training. Using the four-stage process identified in the PRISMA statement the initial number of results (9,369) was reduced to 93. Data (N, mean, SD) were extracted from these articles in duplicate or triplicate. A subset of the data (n = 29 manuscripts) are presented here; manuscripts were included if exercise performance (Time to complete a fixed amount of work: E.g., time trial) and/or capacity (Open ended tests: E.g., Maximal aerobic power, time to exhaustion at a fixed workload), were measured and reported. All HA protocols regardless of duration, frequency, ambient conditions or exercise modality were used. Hedge's g (± 95 % CI) were calculated and correlation analyses were performed between the effect size and total HA time (HAtime), and HA temperature (HAtemp).
The 29 manuscripts reviewed used a mean (± SD) of 9.8 ± 4.0 (range: 4 - 24) HA sessions separated by 0.2 ± 0.4 (0 - 2) days. Total HAtime was 1055 ± 746 min (190 - 3,120), and the HAtemp and HAhumidity were 39.9 ± 5.9 °C (30 - 49) and 34 ± 17 % rh (14 - 87), respectively.
The effect of HA on exercise performance and capacity (n = 7 walking, n = 8 running, n = 13 cycling, n = 1 rowing)
Hedges g(± 95% CI)
0.60 (0.40, 0.81)
+ 21 %
r = 0.22NS
r = 0.11NS
0.58 (0.37, 0.79)
+ 5.3 %
r = 0.67**
r = 0.06NS
- Guy JH, Deakin GB, Edwards AM, Miller CM, Pyne DB: Adaptation to Hot Environmental Conditions: an Exploration of the Performance Basis, Procedures and Future Directions to Optimise Opportunities for Elite Athletes. Sports Med. 2015, 45: 303-311. 10.1007/s40279-014-0277-4.View ArticlePubMedGoogle Scholar
- Chalmers S, Esterman A, Eston R, Bowering KJ, Norton K: Short-Term Heat Acclimation Training Improves Physical Performance: A systematic Review, and Exploration of Physiological Adaptations and Application for Team Sports. Sports Med. 2014, 44: 971-988. 10.1007/s40279-014-0178-6.View ArticlePubMedGoogle Scholar
- Maughan RJ, Shirreffs SM, Ozgunen KT, Kurdak SS, Ersoz G, Binnet MS, Dvorak J: Living, Training and Playing in the Heat: Challenges to the Football Player and Strategies for Coping with Environment Extremes. Scand J Med Sci Sport. 2010, 20 (suppl. 3): 117-124.View ArticleGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.