The walk-run transition (WRT) is a well-described phenomenon without any known cause; however, mechanical variables related to human gait have been associated with the WRT. This study tested the hypothesis that shock waves in the tibia and 3rd lumbar verte­bra in addition to activity of tibialis anterior, vastus lateralis, and erector spinae muscles could be responsible for the WRT. Thirty sub­jects walked and ran on a treadmill at 80%, 90%, 100%, 110%, and 120% of preferred transition speed. Shock waves were measured with skin-mounted accelerometers and muscle activity by surface electromyography. The influence on the WRT was analyzed with two models. The shock waves and muscle activity tended to a significant increase (p < .05) for both walking and running with increased speed. The only factor that appeared to be involved in the WRT mechanism was the activ­ity of the tibialis anterior; however, this was only confirmed by one of the two models. The use of different models to analyze the same data for the WRT triggers may give different results; thus, a standard model is required to investigate the influence of given factors on biological phenomena.
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