Contraction-induced enhancement of relaxation during high force contractions of mouse lumbrical muscle at 37°C

Abstract

Repeated stimulation of unfatigued rodent fast-twitch skeletal muscle accelerates the kinetics of tension relaxation through an unknown mechanism. This effect varies with muscle type and stimulation parameters, and has been observed at physiological temperatures for submaximal but not maximal contractions. The purpose of this study was to compare relaxation kinetics of C57BL/6 mouse lumbrical muscles from maximal isometric force (500 Hz for 20 ms) when evoked before (pre) and after (post) an intervening tetanic contraction at 37°C. During post contractions, we noted significant increases in the rate of tension decline during both the slow linear phase and the fast exponential phase of relaxation, as well as a reduced duration of the slow phase of relaxation compared with pre contractions (all<0.05). This is the first demonstration of enhanced slow and fast relaxation phases from maximal isometric tension induced by prior stimulation in intact muscle at a physiological temperature.

A brief contraction has complex effects on summation of twitch pairs in human adductor pollicis

“…Twitch duration is also affected by contractile history. Mammalian skeletal muscle will commonly exhibit a decrease in twitch duration following a brief contraction, but twitch duration will increase if contractions continue to be applied (Brown & Loeb, 2000; Burke et al., 1976; Carp, Herchenroder, Chen, & Wolpaw, 1999; Celichowski, Grottel, & Bichler, 1999; Celichowski, Pogrzebna, & Raikova, 2005; Cooper & Eccles, 1930; Desmedt & Hainaut, 1968; Krarup, 1981; Krysciak, Celichowski, Krutki, Raikova, & Drzymala‐Celichowska, 2019; Raikova et al., 2008; Smith et al., 2013; Smith, Ali, Power, & Herzog, 2018; Smith, Bellissimo, Herzog, & Tupling, 2016; Smith, Vandenboom, & Tupling, 2014; Smith, Vandenboom, & Tupling, 2017; Smith, Vandenboom, & Tupling, 2019). The mechanism(s) responsible for the contraction‐induced decline in twitch duration have not been resolved, but presumably changes in metabolic reactants and by‐products, myoplasmic calcium, and cyclic interactions of actin and myosin (i.e.…”