The researchers3 have suggested that humans change gait patterns to prevent overexertion and possible injury to the relatively small dorsiflexor muscles which were working close to maximum capacity when walking at or above the preferred WR transition speed. To further investigate muscle behavior in gait transitions, muscle functions have been observed in stance and swing phase separately. Prilutsky and Gregor4 reported that during both walking and running

at all studied constant speeds, the soleus (SL), GA, VL, and GM have their activity bursts primarily during the stance phase, and TA, rectus femoris (RF), and BFL were the major muscles controlling the swing phase. Observation has shown that the activation of muscles with swing-related function (TA, BFL, and RF) is typically lower during running than during walking at preferred running speeds (115%, 130%, and 145% of the preferred

WR transition buy Alisertib Selleckchem GSI-IX speed), and the average EMG activity of muscles with pure support-related functions (SL, GA, VL, and GM) is typically lower during walking than during running at preferred walking speeds (55%, 70%, and 85% of the preferred WR transition speed). Prilutsky and Gregor4 suggested that exaggerated swing-related activation of the TA, RF, and BFL is primarily responsible for the WR transition at increased walking Oxygenase speed and higher support-related activation of the SL, GA, and VL triggers the run to walk (RW) transition at decreasing speed. The abovementioned reports3 and 4 described muscle activity at constant locomotion speed ranges close to preferred gait transition speed and suggested that the gait transitions were an instantaneous event in response to some types of trigger. Other researchers5, 6 and 7 suggested a dynamical systems approach to better describe locomotion mechanisms and predict the various parameters related to gait transition. In applying such an approach, locomotion is treated

as a self-organizing system. Walking and running are distinguished as different attractor states. Gait transitions represent the bifurcations the attractor states experience when velocity is changed as a control parameter. Nonlinear behavior is often observed as systems approach bifurcation, and system behavior changes gradually as it approaches the bifurcation. Recent support to the nonlinear behavior of gait transitions has shown a quadratic trend of vertical ground reaction forces in relation to locomotion speed as approaching toward gait transition.8 and 9 Gait transition related EMG studies3 and 4 only provide possible explanations of muscle activity during stable speeds. They do not mention muscular activity changes as locomotion speeds approach the preferred transition speed as shown with other gait parameters.