TY - JOUR
T1 - Short-Term Heat Acclimation and Precooling, Independently and Combined, Improve 5-km Time Trial Performance in the Heat
AU - James, Carl A.
AU - Richardson, Alan J.
AU - Watt, Peter W.
AU - Willmott, Ashley G. B.
AU - Gibson, Oliver R.
AU - Maxwell, Neil S.
N1 - Publisher Copyright:
© 2018 National Strength and Conditioning Association.
PY - 2018/5
Y1 - 2018/5
N2 - Following heat acclimation (HA), endurance
running performance remains impaired in hot vs. temperate conditions.
Combining HA with precooling (PC) demonstrates no additive benefit in
intermittent sprint, or continuous cycling exercise protocols, during
which heat strain may be less severe compared to endurance running. This study investigated the effect of short-term HA (STHA) combined with mixed methods PC, on endurance
running performance and directly compared PC and HA. Nine amateur
trained runners completed 5-km treadmill time trials (TTs) in the heat
(32° C, 60% relative humidity) under 4 conditions; no intervention
(CON), PC, short-term HA (5 days—HA) and STHA with PC (HA + PC). Mean (±SD)
performance times were; CON 1,476 (173) seconds, PC 1,421 (146)
seconds, HA 1,378 (116) seconds and HA + PC 1,373 (121) seconds. This
equated to the following improvements versus CON; PC −3.7%, HA −6.6% and
HA + PC −7.0%. Statistical differences were only observed between HA
and CON (p = 0.004, d = 0.68, 95% CI [−0.27 to 1.63]) however, similar effect sizes were observed for HA + PC vs. CON (d = 0.70, 95% CI [−0.25 to 1.65]), with smaller effects between PC vs. CON (d = 0.34, 95% CI [−0.59 to 1.27]), HA vs. PC (d = 0.33, 95% CI [−0.60 to 1.26]) and HA + PC vs. PC (d
= 0.36, 95% CI [−0.57 to 1.29]). Pilot testing revealed a TT typical
error of 16 seconds (1.2%). Precooling offered no further benefit to
performance in the acclimated individual, despite modest alleviation of
physiological strain. Maintenance of running speed in HA + PC, despite
reduced physiological strain, may indicate an inappropriate pacing
strategy therefore, further familiarization is recommended to optimize a
combined strategy. Finally, these data indicate HA, achieved through
cycle training, yields a larger ergogenic effect than PC on 5-km running
performance in the heat, although PC remains beneficial when HA is not
possible.
AB - Following heat acclimation (HA), endurance
running performance remains impaired in hot vs. temperate conditions.
Combining HA with precooling (PC) demonstrates no additive benefit in
intermittent sprint, or continuous cycling exercise protocols, during
which heat strain may be less severe compared to endurance running. This study investigated the effect of short-term HA (STHA) combined with mixed methods PC, on endurance
running performance and directly compared PC and HA. Nine amateur
trained runners completed 5-km treadmill time trials (TTs) in the heat
(32° C, 60% relative humidity) under 4 conditions; no intervention
(CON), PC, short-term HA (5 days—HA) and STHA with PC (HA + PC). Mean (±SD)
performance times were; CON 1,476 (173) seconds, PC 1,421 (146)
seconds, HA 1,378 (116) seconds and HA + PC 1,373 (121) seconds. This
equated to the following improvements versus CON; PC −3.7%, HA −6.6% and
HA + PC −7.0%. Statistical differences were only observed between HA
and CON (p = 0.004, d = 0.68, 95% CI [−0.27 to 1.63]) however, similar effect sizes were observed for HA + PC vs. CON (d = 0.70, 95% CI [−0.25 to 1.65]), with smaller effects between PC vs. CON (d = 0.34, 95% CI [−0.59 to 1.27]), HA vs. PC (d = 0.33, 95% CI [−0.60 to 1.26]) and HA + PC vs. PC (d
= 0.36, 95% CI [−0.57 to 1.29]). Pilot testing revealed a TT typical
error of 16 seconds (1.2%). Precooling offered no further benefit to
performance in the acclimated individual, despite modest alleviation of
physiological strain. Maintenance of running speed in HA + PC, despite
reduced physiological strain, may indicate an inappropriate pacing
strategy therefore, further familiarization is recommended to optimize a
combined strategy. Finally, these data indicate HA, achieved through
cycle training, yields a larger ergogenic effect than PC on 5-km running
performance in the heat, although PC remains beneficial when HA is not
possible.
KW - hyperthermia
KW - endurance
KW - lactate threshold
KW - V̇O2max
KW - heat stress
KW - thermoregulation
UR - http://www.scopus.com/inward/record.url?scp=85052677942&partnerID=8YFLogxK
U2 - 10.1519/JSC.0000000000001979
DO - 10.1519/JSC.0000000000001979
M3 - Journal article
C2 - 28486332
AN - SCOPUS:85052677942
SN - 1064-8011
VL - 32
SP - 1366
EP - 1375
JO - Journal of Strength and Conditioning Research
JF - Journal of Strength and Conditioning Research
IS - 5
ER -