Previous research has demonstrated that the preferred transition speed during human locomotion is the speed at which critical levels of ankle angular velocity and acceleration (in the dorsiflexor direction) are reached, leading to the hypothesis that gait transition occurs to alleviate muscular stress on the dorsiflexors. Furthermore, it has been shown that the metabolic cost of running at the preferred transition speed is greater than that of walking at that speed. This increase in energetic cost at gait transition has been hypothesized to occur due to a greater demand being placed on the larger muscles of the lower extremity when gait changes from a walk to a run. This hypothesis was tested by monitoring electromyographic (EMG) activity of the tibialis anterior, medial gastrocnemius, vastus lateralis, biceps femoris, and gluteus maximus while participants (6 M, 3 F) walked at speeds of 70, 80, 90, and 100% of their preferred transition speed, and ran at their preferred transition speed. The EMG activity of the tibialis anterior increased as walking speed increased, then decreased when gait changed to a run at the preferred transition speed. Concurrently, the EMG activity of all other muscles that were monitored increased with increasing walking speed, and at a greater rate when gait changed to a run at the preferred transition speed. The results of this study supported the hypothesis presented.
A. Hreljac, Kinesiology & Health Science, Cal State Sacramento, 6000 J Street, Sacramento, CA 95819-6073; A. Arata, Dept of Kinesiology, USAF Academy, Boulder, CO 80840; R. Ferber, Exercise & Movement Science, U. of Oregon, Eugene, OR 97403; J.A. Mercer, Dept of Kinesiology, UNLV, Las Vegas, NV 89109; B.S. Snow, Center for Locomotion Studies, Penn State, University Park, PA 16802.