Acclimation to moderate heat adequately prepares individuals for work in a hotter environment
conference paper
This work was funded by the Human Sciences Domain of the UK Ministry of Defence Scientific Research Programme.
Optimising the preparation of individuals to perform exercise in a hot environment is typically achieved by implementing a programme of heat acclimation (HA). It is well-established that HA mitigates the problems associated with exercise-heat stress, including a reduction in heat strain and an improvement in physical performance.
PURPOSE: The aim of this study was to establish whether HA in a moderately hot environment (wet bulb globe temperature (WBGT), 26 °C) would prepare individuals to undertake moderate exercise in a hotter environment (WBGT, 32 °C).
METHODS: 15 men exercised on a cycle ergometer for up to 2 hours per day on 12 consecutive days in a hot chamber. The WBGT was 26 °C during the first 9 days (Days 1-9) and 32 °C during the last 3 days (Days 10-12). Rectal temperature (Tre), heart rate (HR), mean skin temperature (Tsk) and sweat rate (SR) were measured during the first 60 minutes of steady state exercise (~45% of maximum oxygen uptake). Thereafter, the tolerance time (TT) was measured during graded cycle exercise to volitional fatigue.
RESULTS: During Days 1-9 (WBGT, 26 °C), Tre reduced to a plateau from 38.7 ± 0.1 to 38.2 ± 0.1 °C(p<0.05), asdidhr(156 ± 10 to 131 ± 11 b-mm-1, p<0.05) and tsk (34.2 ± 0.3 to 33.6 ± 0.2 °c, p<0.05). tt increased to a plateau from 37 ± 2 to 46 ± 1 min (p<0.05). sr was 1.0 ± 0.8 l.h-1 on day 1 and did not change thereafter. during days 10-12 (wbgt, 32 °c), tre, hr, and tsk increased (p<0.05), whereas tt decreased (p<0.05) compared to day 9. however, post-hoc testing showed no significant differences for any of the parameters within the 3 days in the hotter environment.
CONCLUSION: Moderate exercise performed at a WBGT of 26 °C for ~2 hours per day on 9 consecutive days conferred full HA, and no further physiological adaptations were observed when the same exercise was undertaken at a WBGT of 32 °C. We conclude that individuals may be adequately prepared for working in a hotter environment by prior HA in a moderately hot environment.
(NB: this is the complete text)
Optimising the preparation of individuals to perform exercise in a hot environment is typically achieved by implementing a programme of heat acclimation (HA). It is well-established that HA mitigates the problems associated with exercise-heat stress, including a reduction in heat strain and an improvement in physical performance.
PURPOSE: The aim of this study was to establish whether HA in a moderately hot environment (wet bulb globe temperature (WBGT), 26 °C) would prepare individuals to undertake moderate exercise in a hotter environment (WBGT, 32 °C).
METHODS: 15 men exercised on a cycle ergometer for up to 2 hours per day on 12 consecutive days in a hot chamber. The WBGT was 26 °C during the first 9 days (Days 1-9) and 32 °C during the last 3 days (Days 10-12). Rectal temperature (Tre), heart rate (HR), mean skin temperature (Tsk) and sweat rate (SR) were measured during the first 60 minutes of steady state exercise (~45% of maximum oxygen uptake). Thereafter, the tolerance time (TT) was measured during graded cycle exercise to volitional fatigue.
RESULTS: During Days 1-9 (WBGT, 26 °C), Tre reduced to a plateau from 38.7 ± 0.1 to 38.2 ± 0.1 °C(p<0.05), asdidhr(156 ± 10 to 131 ± 11 b-mm-1, p<0.05) and tsk (34.2 ± 0.3 to 33.6 ± 0.2 °c, p<0.05). tt increased to a plateau from 37 ± 2 to 46 ± 1 min (p<0.05). sr was 1.0 ± 0.8 l.h-1 on day 1 and did not change thereafter. during days 10-12 (wbgt, 32 °c), tre, hr, and tsk increased (p<0.05), whereas tt decreased (p<0.05) compared to day 9. however, post-hoc testing showed no significant differences for any of the parameters within the 3 days in the hotter environment.
CONCLUSION: Moderate exercise performed at a WBGT of 26 °C for ~2 hours per day on 9 consecutive days conferred full HA, and no further physiological adaptations were observed when the same exercise was undertaken at a WBGT of 32 °C. We conclude that individuals may be adequately prepared for working in a hotter environment by prior HA in a moderately hot environment.
(NB: this is the complete text)
TNO Identifier
19078
Source title
Medicine & Science in Sports & Exercise
Pages
S308
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