Key result
Four weeks of uphill or downhill running induced serial sarcomere number adaptations in rats but did not modify residual force enhancement or depression at the whole-muscle level.
Why the study?
The study was designed to investigate the trainability of residual force enhancement and residual force depression based on serial sarcomere number alterations to history-dependent force properties.
Does 4 weeks of uphill or downhill running alter residual force enhancement or depression in rat muscles?
Does 4 weeks of uphill or downhill running alter residual force enhancement or depression in rat muscles?
Training-induced serial sarcomere number adaptations do not modify residual force enhancement or depression at the whole-muscle level in rats.
Rat training altered SSN without affecting rFE/rFD; leaves open whether history-dependent properties are trainable in humans.
The increase or decrease in isometric force following active muscle lengthening or shortening, relative to a reference isometric contraction at the same muscle length and level of activation, are referred to as residual force enhancement (rFE) and residual force depression (rFD), respectively. The purpose of these experiments was to investigate the trainability of rFE and rFD on the basis of serial sarcomere number (SSN) alterations to history-dependent force properties. Maximal rFE/rFD measures from the soleus and extensor digitorum longus (EDL) of rats were compared after 4 weeks of uphill or downhill running with a no-running control. SSN adapted to the training: soleus SSN was greater with downhill compared with uphill running, while EDL demonstrated a trend towards more SSN for downhill compared with no running. In contrast, rFE and rFD did not differ across training groups for either muscle. As such, it appears that training-induced SSN adaptations do not modify rFE or rFD at the whole-muscle level.
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Chen et al. (2020) studied this question. Uphill or downhill running vs. No-running control was evaluated on Maximal residual force enhancement (rFE) and residual force depression (rFD). Four weeks of uphill or downhill running induced serial sarcomere number adaptations in rats but did not modify residual force enhancement or depression at the whole-muscle level.
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