Abstract
Research has shown that compression of muscle can lead to a change in muscle force. Most studies show compression to lead to a reduction in muscle force, although recent research has shown that increases are also possible. Based on methodological differences in the loading design between studies, it seems that muscle length and the direction of transverse loading influence the effect of muscle compression on force production. Thus, in our current study we implement these two factors to influence the effects of muscle loading. In contrast to long resting length of the medial gastrocnemius (MG) in most studies, we use a shorter MG resting length by having participant seated with their knees at a 90° angle. Where previous studies have used unidirectional loads to compress the MG, in this study we applied a multidirectional load using a sling setup. Multidirectional loading using a sling setup has been shown to cause muscle force reductions in previous research. As a result of our choices in experimental design we observed changes in the effects of muscle loading compared to previous research. In the present study we observed no changes in muscle force due to muscle loading. Muscle thickness and pennation angle showed minor but significant increases during contraction. However, no significant changes occurred between unloaded and loaded trials. Fascicle thickness and length showed different patterns of change compared to previous research. We show that muscle loading does not result in force reduction in all situations and is possibly linked to differences in muscle architecture and muscle length.
Highlights
IntroductionResearch has shown that applying unidirectional transverse loads to the gastrocnemius in rats will lead to a reduction in muscle force of nearly 13% (Siebert et al, 2014a)
Muscle force is affected by compression applied to the muscle
For the passive state, the transverse load resulted in a significant decrease in the pennation angle [F(3, 180) = 11.4, p < 0.001, η2p = 0.160] (Figures 3A,B) and the muscle thickness (Figures 3C,D), but not in the fascicle length or transverse wavelength (Figures 3C–H)
Summary
Research has shown that applying unidirectional transverse loads to the gastrocnemius in rats will lead to a reduction in muscle force of nearly 13% (Siebert et al, 2014a). More recently it was shown that unidirectional transverse loads have a similar effect on the human gastrocnemius where a 16% force reduction was measured at higher loads (Ryan et al, 2019; Stutzig et al, 2019). Siebert et al (2018) showed that multidirectional transverse loading caused reductions in twitch force, but these reductions were less than for the unidirectional transverse loads. Finite element modeling has shown that force reduction due to compression of the muscle is dependent on both pennation angle and initial muscle length (Ryan et al, 2020)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
