Muscle can experience post-activation potentiation (PAP), a temporary increase in force and rate of force development, when contractions are closely timed; therefore, cyclical behaviours are likely affected by PAP, as succeeding contraction cycles can lead to potentiation over several subsequent cycles. Here, we examined PAP during in situ cyclical contractions of the mallard lateral gastrocnemius (LG). Surface swimming, a cyclical behaviour, was mimicked with work-loops using in vivo LG length change and stimulation parameters. Tests were performed at mallards' preferred cycle frequency as well as at lower and higher frequencies. Like muscles from mammals, anurans and arthropods, the mallard LG exhibited PAP with increases in peak force, average force rate and net work. Staircase potentiation occurred over two or more work-loop cycles, resulting in gradual increases in PAP. The number of cycles needed to reach maximum work varied with cycle frequency, requiring more cycles at higher cycle frequencies. PAP occurred under in vivo-like stimulation parameters, suggesting a potentially important role of PAP in animal locomotion, especially in cyclical behaviours.

中文翻译：

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激活后的肌肉增强作用及其与周期性行为的相关性。

当收缩时间紧迫时，肌肉会经历激活后增强（PAP），即力量的暂时增加和力量的发展速度；因此，周期性行为可能会受到PAP的影响，因为随后的收缩循环可能导致随后几个循环的增强。在这里，我们检查了野鸭外侧腓肠肌（LG）的原位周期性收缩过程中的PAP。使用体内LG长度变化和刺激参数，通过工作循环模仿表面游泳（一种周期性行为）。在野鸭的首选循环频率以及较低和较高的频率下进行测试。像来自哺乳动物，无脊椎动物和节肢动物的肌肉一样，绿头鸭LG表现出PAP，峰值力，平均力率和净功增加。楼梯增强发生在两个或多个工作循环周期中，导致PAP逐渐增加。达到最大工作所需的循环数随循环频率而变化，在较高的循环频率下需要更多的循环。PAP在类似体内的刺激参数下发生，表明PAP在动物运动中，尤其是在周期性行为中具有潜在的重要作用。