Post-activation muscle potentiation and its relevance to cyclical behaviours

Abstract

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.

Posttetanic potentiation improves neuromuscular efficiency of mouse muscle in vitro

“…Far from being restricted to rodents, force potentiation phenomena may be a ubiquitous feature of muscle performance in nature. For example, potentiation has been observed in muscles or muscle fibers from such diverse species as birds (Taylor-Burt et al, 2020), cats (Brown & Loeb, 1998), dogs (Martin-Flores et al, 2011, frogs (Vergara et al, 1977), insects (Dickinson et al, 1997), T A B L E 2 Effect of tetanic protocol on work output at different frequencies and spiders (Padrón et al, 2020). Based on this, it is difficult to argue that potentiation mechanisms are not highly relevant for the locomotion of animals and humans.…”