Meeting Abstract
Predation is an important factor that shapes prey’s fitness. Kangaroo rats (D. deserti) are bipedal hoppers that do not only outrun but also ‘out-jump’ predators, as they perform vertical jumps to evade their attacker (i.e., snakes and owls). Reported vertical jumps of this animal can reach more than 1 meter, which is over 20 times hip height; however under laboratory conditions, we see maximal jumps of approximately 10 times hip height. The lateral gastrocnemius muscle (LG) is one of the primary muscles involved in plantar flexion, and likely plays a key role in propelling the animal upwards during vertical jumping. In this study we examined the relative mechanical work contribution by the LG muscle to the vertical jumps of kangaroo rats. We hypothesized that the amount of work done by the LG is a fixed percentage of the energy required for a jump. We examined the in vivo performance of the LG muscle during vertical jumping by combining high speed video and ground reaction forces for inverse dynamics, along with sonomicrometry and EMG data. Preliminary data suggest that our hypothesis is supported. There appears to be a linear relationship between actual jump height and work done by the LG muscle. This suggests that the LG muscle is required to perform more work as the height of the jump-task increases. Future research will include a more detailed analysis of joint and muscle dynamics as well as analysis of additional leg muscles.
