During jumping by kangaroo rats, the musculotendon work contributions across all joints are not well understood. Namely, measures of external joint work do not provide information on the contributions from individual muscles or in-series elastic structures. In this study, we examined the functional roles of a major ankle extensor muscle, lateral gastrocnemius (LG), and of a major knee extensor muscle, vastus lateralis (VL), through in vivo sonomicrometry and electromyography techniques, during vertical jumping by kangaroo rats. Our data showed that both muscles increased shortening and activity with higher jumps. We found that knee angular velocity and VL muscle shortening velocity were coupled in time. In contrast, the ankle angular velocity and LG muscle shortening velocity were decoupled, and rapid joint extension near the end of the jump produced high power outputs at the ankle joint. Further, the decoupling of muscle and joint kinematics allowed the LG muscle to prolong the period of shortening velocity near optimal velocity (Vopt), which likely enabled the muscle to sustain maximal power generation. These observations were consistent with a LG tendon that is much more compliant than that of the VL.
Plantar flexor muscles of kangaroo rats (D. deserti) shorten at a velocity to produce optimal power during jumping
- Award Group:
- Funder(s): National Science Foundation
- Award Id(s): 1553550
- Funder(s):
- Award Group:
- Funder(s): Army Research Office
- Award Id(s): 66554-EG
- Funder(s):
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M. Janneke Schwaner, David C. Lin, Craig P. McGowan; Plantar flexor muscles of kangaroo rats (D. deserti) shorten at a velocity to produce optimal power during jumping. J Exp Biol 2021; jeb.242630. doi: https://doi.org/10.1242/jeb.242630
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