Hamilton Alan R, Behm David G
Kinesiology, School of Human Kinetics and Recreation, Memorial University of Newfoundland, 230 Elizabeth Ave., St. John's, NL, A1C 5S7, Canada.
Eur J Appl Physiol. 2017 Apr;117(4):651-663. doi: 10.1007/s00421-016-3526-4. Epub 2017 Feb 27.
If the work duration or volume is known, it is common for individuals to anticipate this challenge by pursuing a strategy that may decrease the initial force output and maintain a force level that ensures a force reserve towards the end of the task. However, it is unknown whether this is a global strategy that is transferred to a non-exercised muscle following fatigue of a contralateral homologous muscle.
To clarify if prior knowledge of task endpoint has an effect on non-local muscle fatigue (NLMF), 15 male participants (22.4 ± 3.8 years) completed four conditions: (1) KNtest > fatigue (known endpoint after fatigue), (2) UNKtest > fatigue (unknown endpoint after fatigue), (3) KNtest > control (known endpoint without fatigue), (4) UNKtest > control (unknown endpoint without fatigue). For fatigue conditions, a maximal intensity, unilateral knee extension protocol was completed (two sets of 100 s maximal voluntary isometric contractions (MVIC) with 60 s rest between), whereas the control condition involved rest (260 s). The participants were either informed (known (KN) conditions) or not informed (unknown (UNK) conditions) of the duration of a post-intervention strength-endurance test (contralateral knee extension MVIC, ≥30 s).
During the strength-endurance test, the UNKtest > fatigue displayed meaningful decreases in force (UNKtest > fatigue 10-12% over first 30 s), which was largest at the 25-30-s period (UNKtest > fatigue 7.4-41.1% from 25 to 1930s) compared to KNtest > fatigue and KNtest > control conditions, respectively.
Prior knowledge of task endpoint can modify NLMF and affect pacing strategies.
如果工作持续时间或工作量已知，个体通常会通过采取一种策略来应对这一挑战，该策略可能会降低初始力量输出，并维持一个能确保在任务结束时仍有力量储备的力量水平。然而，尚不清楚这是否是一种在对侧同源肌肉疲劳后转移至未锻炼肌肉的通用策略。
为了阐明对任务终点的先验知识是否会对非局部肌肉疲劳（NLMF）产生影响，15名男性参与者（22.4±3.8岁）完成了四种情况的测试：（1）已知终点>疲劳（疲劳后已知终点），（2）未知终点>疲劳（疲劳后未知终点），（3）已知终点>对照（无疲劳的已知终点），（4）未知终点>对照（无疲劳的未知终点）。对于疲劳情况，完成了一项最大强度的单侧膝关节伸展方案（两组100秒的最大自主等长收缩（MVIC），每组之间休息60秒），而对照情况则是休息（260秒）。参与者被告知（已知（KN）情况）或未被告知（未知（UNK）情况）干预后力量耐力测试（对侧膝关节伸展MVIC，≥30秒）的持续时间。
在力量耐力测试期间，未知终点>疲劳组的力量出现了显著下降（未知终点>疲劳组在前30秒内下降了10 - 12%），与已知终点>疲劳组和已知终点>对照组相比，在25 - 30秒期间下降幅度最大（未知终点>疲劳组从25秒到30秒下降了7.4 - 41.1%）。
对任务终点的先验知识可以改变非局部肌肉疲劳并影响节奏策略。
