Laboratory of Exercise Physiology (EA4338), University of Lyon, Saint-Etienne, France.
PLoS One. 2012;7(8):e43586. doi: 10.1371/journal.pone.0043586. Epub 2012 Aug 22.
Trekking and military missions generally consist of carrying heavy loads for extreme durations. These factors have been separately shown to be sources of neuromuscular (NM) fatigue and locomotor alterations. However, the question of their combined effects remains unresolved, and addressing this issue required a representative context.
The aim was to investigate the effects of extreme-duration heavy load carriage on NM function and walking characteristics.
Ten experienced infantrymen performed a 21-h simulated military mission (SMM) in a middle-mountain environment with equipment weighing ∼27 kg during battles and ∼43 kg during marches. NM function was evaluated for knee extensors (KE) and plantar flexors (PF) pre- and immediately post-SMM using isometric maximal voluntary contraction (MVC) measurement, neural electrical stimulation and surface EMG. The twitch-interpolation method was used to assess central fatigue. Peripheral changes were examined by stimulating the muscle in the relaxed state. The energy cost, mechanical work and spatio-temporal pattern of walking were also evaluated pre-/post-SMM on an instrumented treadmill in three equipment conditions: Sportswear, Battle and March.
After the SMM, MVC declined by -10.2±3.6% for KE (P<0.01) and -10.7±16.1% for PF (P = 0.06). The origin of fatigue was essentially peripheral for both muscle groups. A trend toward low-frequency fatigue was detected for KE (5.5%, P = 0.08). These moderate NM alterations were concomitant with a large increase in perceived fatigue from pre- (rating of 8.3±2.2) to post-SMM (15.9±2.1, P<0.01). The SMM-related fatigue did not alter walking energetics or mechanics, and the different equipment carried on the treadmill did not interact with this fatigue either.
this study reports the first data on physiological and biomechanical consequences of extreme-duration heavy load carriage. Unexpectedly, NM function alterations due to the 21-h SMM were moderate and did not alter walking characteristics.
Name: Effect of prolonged military exercises with high load carriage on neuromuscular fatigue and physiological/biomechanical responses. Number: NCT01127191.
研究极端时间长负荷行军对神经肌肉（NM）功能和行走特征的影响。
10 名经验丰富的步兵在山区环境中进行了 21 小时的模拟军事任务（SMM），装备重量约为 27 公斤（在战斗中）和 43 公斤（在行军中）。使用等长最大自主收缩（MVC）测量、神经电刺激和表面肌电图在 SMM 前后对膝关节伸肌（KE）和足底屈肌（PF）的 NM 功能进行评估。使用 twitch-interpolation 方法评估中枢疲劳。通过在肌肉松弛状态下刺激肌肉来检查外周变化。还在装有仪器的跑步机上在三种设备条件下（运动服、战斗和行军）评估行走的能量消耗、机械功和时空模式：运动服、战斗和行军。
SMM 后，KE 的 MVC 下降了-10.2±3.6%（P<0.01），PF 的 MVC 下降了-10.7±16.1%（P=0.06）。两组肌肉的疲劳源主要为外周性。KE 出现低频疲劳趋势（5.5%，P=0.08）。这些中度 NM 改变与从 SMM 前（评分 8.3±2.2）到后（15.9±2.1，P<0.01）的感知疲劳的大幅增加有关。SMM 相关的疲劳并没有改变行走的能量学或力学，并且在跑步机上携带的不同设备也没有与这种疲劳相互作用。
本研究首次报道了长时间高强度负荷行军对神经肌肉和生物力学的影响。出乎意料的是，21 小时 SMM 引起的 NM 功能改变是中度的，没有改变行走特征。
名称：长时间高强度负荷行军对神经肌肉疲劳和生理/生物力学反应的影响。编号：NCT01127191。
