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Skeletal Muscle
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
Most skeletal muscles of the body have a different mix of the three types of muscle fibers, depending on their type of activity. Thus, postural muscles of the leg, back, and neck have a higher proportion of type I fibers. The soleus, a powerful muscle in the back of the calf that is involved in standing and walking, contains 60%–100% slow fibers in humans. On the other hand, muscles of the shoulder and arms have a higher proportion of type IIB fibers because they are usually used only intermittently, and for short periods, to produce a relatively large force for activities such as lifting.
Are We Built to Stand?
Published in Robert Bridger, A Guide to Active Working in the Modern Office, 2019
Plantar flexion of the ankle joint (pointing the toes downwards when sitting, or standing on tip-toe) activates the muscle pump (mainly through contraction of the soleus, or calf muscles) and pumps blood back up to the heart against gravity.
Alterations in Achilles tendon stress and strain across a range of running velocities
Published in Journal of Sports Sciences, 2023
Bryce Ertman, Melissa Klaeser, Lucas Voie, Naghmeh Gheidi, C. Nathan Vannatta, Drew Rutherford, Thomas W. Kernozek
When analysing the muscular components of AT force (soleus and gastrocnemius forces) in this study, greater involvement of the soleus was observed across running speeds. The soleus individually averaged greater than 2.9%BW of force compared to the gastrocnemius force (Table 1). This is likely due to the anatomical positioning of the plantar flexor muscles during the push-off phase of gait, where peak AT force is typically achieved (Almonroeder et al., 2013; Lyght et al., 2016). While the soleus appears to be the primary force contributor and always higher than the gastrocnemius through mid-stance while running at the speeds selected in our study, the gastrocnemius forces seemed to show a greater relative change from 4.0 m/s to 5.0 m/s (Figure 1b,c). The increases in soleus and gastrocnemius forces across the running speeds tested in this study support the notion that the soleus and gastrocnemius play a primary role in vertical support when changing speed across slow and medium speeds (Dorn et al., 2012). Thus, it seems reasonable to conclude that recreational runners seeking to increase their running speed within the range of 2.0–5.0 m/s may experience a significant increase in loads to the musculotendinous structures of the triceps surae muscle–tendon complex.