School of Science, University of Derby, Kedleston Road, Derby, DE22 1GB, UK,
Eur J Appl Physiol. 2014 May;114(5):1085-93. doi: 10.1007/s00421-014-2839-4. Epub 2014 Feb 15.
We investigated the effect of carrying a 25 kg backpack upon exercise-induced respiratory muscle fatigue, pulmonary function and physiological and perceptual responses to exercise.
Nineteen healthy males performed 60 min walking at 6.5 km h(-1) and 0 % gradient with a 25 kg backpack (load carriage; LC). Following 15 min recovery participants then completed a 2.4 km time trial with the load (LCTT) and on a different day, repeated the trials without the load [control trial (CON) and control time trial (CONTT), respectively]. Respiratory muscle fatigue was determined by the transient change in maximal inspiratory (P Imax) and expiratory (P Emax) pressure prior to and immediately following exercise.
P Imax and P Emax were reduced from baseline by 11 and 13 % (P < 0.05), respectively, post-LC but remained unchanged post-CON. Following the time trial P Imax and P Emax were reduced 16 and 19 %, respectively, post-LCTT (P < 0.05) and by 6 and 10 %, respectively (P < 0.05), post-CONTT compared to baseline. Both forced vital capacity and forced expiratory volume in 1 s were reduced by 4 ± 13 and 1 ± 9 %, respectively, during LC when compared to CON. Relative to CON all physiological and perceptual responses were greater in LC, both post-LC and -LCTT (P < 0.01). Time trial performance was faster during CONTT (11.08 ± 1.62 min) relative to LCTT (15.93 ± 1.91 min; P < 0.05).
This study provides novel evidence that constant speed walking and time trial exercise with 25 kg thoracic load carriage induces significant inspiratory and expiratory muscle fatigue and may have important performance implications in some recreational and occupational settings.
我们研究了背负 25 公斤背包对运动诱导性呼吸肌疲劳、肺功能以及运动时生理和知觉反应的影响。
19 名健康男性以 6.5 公里/小时和 0%坡度进行 60 分钟的步行，携带 25 公斤背包（负重）。15 分钟恢复期后，参与者携带负荷进行 2.4 公里计时赛（LCTT），而在另一天，不携带负荷重复进行试验[对照试验（CON）和对照计时赛（CONTT）]。呼吸肌疲劳通过运动前和运动后即刻最大吸气（PImax）和最大呼气（PEmax）压力的瞬态变化来确定。
LC 后 PImax 和 PEmax 分别降低了 11%和 13%（P<0.05），而 CON 后则无变化。计时赛后，PImax 和 PEmax 分别降低了 16%和 19%（P<0.05），LCTT 后分别降低了 6%和 10%（P<0.05），而 CONTT 后与基线相比分别降低了 6%和 10%（P<0.05）。与 CON 相比，LC 时用力肺活量和 1 秒用力呼气量分别降低了 4%±13%和 1%±9%。与 CON 相比，LC 后和 LCTT 后所有生理和知觉反应均更大（P<0.01）。CONTT 时的计时赛表现更快（11.08±1.62 分钟），而 LCTT 时则更慢（15.93±1.91 分钟；P<0.05）。
本研究提供了新的证据，表明恒定速度步行和 25 公斤胸带负重计时赛会引起显著的吸气和呼气肌疲劳，并且可能对某些娱乐和职业环境中的表现产生重要影响。
