Abstract
The steady‐state isometric force following active muscle shortening or lengthening is smaller (force depression, FD) or greater (residual force enhancement, RFE) than a purely isometric contraction at the corresponding length. The mechanism underlying these phenomena is not explained within the context of the cross‐bridge theory, with few studies investigating the effects of FD and RFE in stretching–shortening cycle (SSC). The purpose of this study was to perform SSC, where the time between the end of stretch and the end of shortening was manipulated by (1) adding a pause between stretch and shortening (protocol 1) or (2) performing the shortening contraction at different speeds (protocol 2). The results show that, in protocol 1, FD was reduced for SSC with a 0‐sec and 0.5‐sec interval between stretching and shortening, but was the same for SSC with a 1‐sec interval compared to the pure FD condition. In protocol 2, FD was reduced for SSC with shortening speeds of 30 and 60°/sec, but was the same for shortening speeds of 15 and 20°/sec compared to the pure FD condition. These findings provide evidence that stretch preceding shortening affects FD in a time‐ and speed‐dependent manner, providing new information on the potential mechanism of FD and RFE.
Highlights
Muscle force production has been shown to be history dependent (Abbott and Aubert 1952; Marechal and Plaghki 1979; Edman et al 1982; Joumaa et al 2008; Herzog, 2014)
History-dependent muscle properties cause that the steady-state isometric force following an active shortening or lengthening contraction is smaller or greater compared to a purely isometric contraction at the corresponding muscle length and same level of activation
Contrary to the results reported by Herzog and Leonard (2000) and Lee et al (2001), Seiberl et al (2015) found that Residual force enhancement (RFE) was abolished during the shortening phase of stretch–shortening cycles (SSCs) for fast stretch– shortening contractions, with the authors suggesting that the RFE acquired during active muscle stretching might have been abolished in a transient manner during shortening
Summary
Muscle force production has been shown to be history dependent (Abbott and Aubert 1952; Marechal and Plaghki 1979; Edman et al 1982; Joumaa et al 2008; Herzog, 2014). History-dependent muscle properties cause that the steady-state isometric force following an active shortening or lengthening contraction is smaller (force depression; FD) or greater (residual force enhancement; RFE) compared to a purely isometric contraction at the corresponding muscle length and same level of activation Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society. Despite being well-documented across all structural levels of muscle over the last 50 years, and observed during electrically stimulated (Lee et al 2001; Seiberl et al 2015; Fortuna et al 2016) and voluntary contractions in humans (Lee and Herzog 2002; Power et al 2014a,b), the mechanism behind these history-dependent phenomena remains unknown
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