Kirby Nathalie V, Lucas Samuel J E, Lucas Rebekah A I
School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, United Kingdom.
Front Physiol. 2019 May 16;10:539. doi: 10.3389/fphys.2019.00539. eCollection 2019.
Although emerging as a cost and time efficient way to prepare for competition in the heat, recent evidence indicates that "short-term" heat acclimation (<7 days) may not be sufficient for females to adapt to repeated heat stress. Furthermore, self-paced performance following either short-term, or longer (>7 days) heat acclimation has not been examined in a female cohort. Therefore, the aim of this study was to investigate self-paced endurance performance in hot conditions following 4- and 9-days of a high-intensity isothermic heat acclimation protocol in a female cohort. Eight female endurance athletes (mean ± SD, age 27 ± 5 years, mass 61 ± 5 kg, VO 47 ± 6 ml⋅kg⋅min) performed 15-min self-paced cycling time trials in hot conditions (35°C, 30%RH) before (HTT1), and after 4-days (HTT2), and 9-days (HTT3) isothermic heat acclimation (HA, with power output manipulated to increase and maintain rectal temperature ( ) at ∼38.5°C for 90-min cycling in 40°C, 30%RH) with permissive dehydration. There were no significant changes in distance cycled ( = 0.47), mean power output ( = 0.55) or cycling speed ( = 0.44) following 4-days HA (i.e., from HTT1 to HTT2). Distance cycled (+3.2%, = 0.01; +1.8%, = 0.04), mean power output (+8.1%, = 0.01; +4.8%, = 0.05) and cycling speed (+3.0%, = 0.01; +1.6%, = 0.05) were significantly greater in HTT3 than in HTT1 and HTT2, respectively. There was an increase in the number of active sweat glands per cm in HTT3 as compared to HTT1 (+32%; = 0.02) and HTT2 (+22%; < 0.01), whereas thermal sensation immediately before HTT3 decreased ("Slightly Warm," = 0.03) compared to ratings taken before HTT1 ("Warm") in 35°C, 30%RH. Four-days HA was insufficient to improve performance in the heat in females as observed following 9-days HA.
尽管作为一种在炎热环境中为比赛做准备的经济高效方式逐渐兴起，但最近的证据表明，“短期”热适应（<7天）可能不足以让女性适应反复的热应激。此外，在女性群体中，尚未研究短期或长期（>7天）热适应后的自定节奏运动表现。因此，本研究的目的是调查在女性群体中，经过4天和9天高强度等温热适应方案后，在炎热条件下的自定节奏耐力表现。八名女性耐力运动员（平均±标准差，年龄27±5岁，体重61±5千克，VO₂max 47±6毫升·千克·分钟⁻¹）在热环境（35°C，30%相对湿度）下，在等温热适应（HA）前（HTT1）、4天后（HTT2）和9天后（HTT3）进行了15分钟的自定节奏骑行计时赛（HA期间，通过控制功率输出，在40°C、30%相对湿度下骑行90分钟，使直肠温度维持在约38.5°C，并允许脱水）。4天HA后（即从HTT1到HTT2），骑行距离（P = 0.47）、平均功率输出（P = 0.55）或骑行速度（P = 0.44）均无显著变化。HTT3中的骑行距离（分别增加3.2%，P = 0.01；增加1.8%，P = 0.04）、平均功率输出（分别增加8.1%，P = 0.01；增加4.8%，P = 0.05）和骑行速度（分别增加3.0%，P = 0.01；增加1.6%，P = 0.05）均显著高于HTT1和HTT2。与HTT1相比，HTT3中每平方厘米活跃汗腺数量增加（+32%，P = 0.02），与HTT2相比也增加（+22%，P < 0.01），而在HTT3前的热感觉与在35°C、30%相对湿度下HTT1前的评级（“温暖”）相比有所下降（“稍暖”，P = 0.03）。如9天HA后所观察到的，4天HA不足以提高女性在炎热环境中的运动表现。
