Abstract Purpose The purpose of this study was to investigate lower extremity neuromuscular activity patterns during gait transitions with continuously changing locomotion speeds. Methods Muscular activities related to gait transitions (walk to run and run to walk) induced by changing treadmill speed were compared to muscular activities during walk and run at constant speeds. All transition and constant speed conditions were conducted in similar speed range. Surface electromyographic activities of gluteus maximus (GM), rectus femoris (RF), vastus lateralis (VL), biceps femoris long head (BFL), tibialis anterior (TA), gastrocnemius (GA), and soleus (SL) were collected and analyzed. The influences of speed and mode of locomotion were analyzed. Results We have observed transition specific nonlinear muscular behavior in this study. For example, peak magnitudes of GM, RF, GA, and SL increased with speed quadratically as locomotion approached walk to run transition within the last five steps. Activity duration of GA decreased in a quadratic fashion with speed as approached run to walk transition within the last five steps. These nonlinear reactions to speed change were only observed in transition related conditions but not in the constant speed conditions. Conclusion These results indicated that, in preparation for transition, neuromuscular modifications occur steps before gait transition due to changing speed. Gait transition is not a spontaneous event in response to any type of triggers.