Muscle power attenuation by tendon during energy dissipation

Abstract

An important function of skeletal muscle is deceleration via active muscle fascicle lengthening, which dissipates movement energy. The mechanical interplay between muscle contraction and tendon elasticity is critical when muscles produce energy. However, the role of tendon elasticity during muscular energy dissipation remains unknown. We tested the hypothesis that tendon elasticity functions as a mechanical buffer, preventing high (and probably damaging) velocities and powers during active muscle fascicle lengthening. We directly measured lateral gastrocnemius muscle force and length in wild turkeys during controlled landings requiring rapid energy dissipation. Muscle-tendon unit (MTU) strain was measured via video kinematics, independent of muscle fascicle strain (measured via sonomicrometry). We found that rapid MTU lengthening immediately following impact involved little or no muscle fascicle lengthening. Therefore, joint flexion had to be accommodated by tendon stretch. After the early contact period, muscle fascicles lengthened and absorbed energy. This late lengthening occurred after most of the joint flexion, and was thus mainly driven by tendon recoil. Temporary tendon energy storage led to a significant reduction in muscle fascicle lengthening velocity and the rate of energy absorption. We conclude that tendons function as power attenuators that probably protect muscles against damage from rapid and forceful lengthening during energy dissipation.

Is human Achilles tendon deformation greater in regions where cross-sectional area is smaller?

“…The lower stiffness of the proximal Achilles tendon region may allow it to function as a 'buffer', absorbing high strains induced by high force eccentric contractions and thereby protecting the stiffer, more highly stressed, distal portion of the Achilles tendon. The capacity of the tendon to act as a buffer and protect the muscle fascicles from injury by attenuating the force and slowing the rate of lengthening for muscle fascicles has previously been identified (Konow and Roberts, 2015;Konow et al, 2012;Roberts and Konow, 2013). We speculate that the proximal portion of the Achilles tendon may function as a buffer not only to protect the muscle fascicles but also to protect the stiffer, more highly stressed, distal portion of the Achilles tendon.…”

Muscle fascicle shortening behaviour of vastus lateralis during a maximal force–velocity test

“…These interactions have been well described in animal (Astley and Roberts 2012;Biewener and Baudinette 1995;Wilson et al 2003) and human locomotion (e.g., walking and running; Cronin and Lichtwark 2013;Fukunaga et al 2001;Ishikawa et al 2007;Lichtwark et al 2007). During exercises involving stretch-shortening cycles, these interactions have been demonstrated to enhance the work produced by the muscle-tendon unit (Ishikawa and Komi 2004;Kawakami et al 2002;Finni et al 2001), to improve the efficiency (Lichtwark and Barclay 2010) and to reduce muscle fibre elongation during the eccentric phase, thereby limiting the risk of strain induced injury (Guilhem et al 2016;Konow et al 2012).…”

Locomotion as an emergent property of muscle contractile dynamics

“…In the absence of a free tendon, which contributes to the series elasticity of an MTU, length changes of the muscle's fibers more effectively control or produce motions of the skeleton at a joint. Although recent work shows that the passive elasticity of a free tendon or aponeurosis may protect a muscle's fibers from potential damage when rapidly stretched (Konow et al, 2012;Roberts and Azizi, 2010) and can also modulate the F-V effects of the muscle's fibers to produce force with greater efficiency (Lichtwark and Wilson, 2005;Roberts, 2002), passive elasticity of connective tissue in series with a muscle's fibers limits the ability of the fibers to control movement at a skeletal attachment site. Extreme examples are the very short (6-12 mm) pinnate fibered superficial (SDF) and deep digital flexor (DDF) and plantaris (PL) muscles of horses and other large ungulates, which attach to the distal phalanges via long (∼600 mm) tendons (Alexander, 2002;Biewener, 1998b;Wilson et al, 2001).…”