Muscle Activation in Healthy Subjects during Single Step Up

BACKGROUND: The single step up is an integral movement performance for functional mobility and activities of daily living. During this activity the body has to be able to keep its balance and maintain a stable upright posture for performing voluntary movement. For this purpose the central nervous system creates different motor programs specific to the task. A motor programme is believed to contain the pre-programmed sequence of muscle activity prior to the initiation of the task, and includes both the muscle activity for the task, as well as postural muscle activity.OBJECTIVE: The aim of this paper was to examine the sequence of muscular activation, and to determine the timing of the involvement of selected trunk and leg muscles whilst stepping up. The further aim was to find out the most common muscle patterns in this model of motor activity in healthy subjects.METHODS: The bilateral electromyographic (EMG) signal from the gluteus maximus, biceps femoris and erectores spinae muscles were recorded using surface electromyography. The visual record of the step up performance was registered simultaneously with surface electromyography. The tested group consisted of 16 healthy (5 men with an average age of 23.6, 11 women with an average age of 23.2). They were monitored during the motor task-the step up task, that is which was performed by the dominant leg. The subject stood facing the step (height of the step =20 cm). Upon request he/she stepped up with the right leg at a spontaneous speed. The motor task was completed by bringing the left leg up onto the step.RESULTS: During this task, we registered the activation of the right erector spinae muscle, right biceps femoris muscle, left erector spinae muscle and left biceps femoris muscle before the beginning of the visually recognizable movement. The most frequently registered pattern of activation on the side that carried out the step was: right biceps femoris muscle→right erector spinae muscle→right gluteus maximus muscle. Greater differences in the sequence of the muscle involvement were found on the side of the supporting leg.CONCLUSIONS: In conclusion, the findings have indicated that there exists variability in patterns of muscle activation during the step up task.