Developmental Changes of Muscle Synergies in an Infant's Walking.

Primitive stepping is one of the primitive reflexes in newborns in response to external stimuli. It is known that primitive stepping disappears about two months after birth, but its role and the relationship with voluntary gait acquired later are still unknown. In this study, we extracted muscle synergies, spatiotemporal coordination patterns of muscle activities, from EMG measured in one infant during growth (4-18 weeks of age) using non-negative matrix factorization (NMF).

Electromyographic developmental changes in one individual from newborn stepping to mature walking.

Electromyographic (EMG) recordings of the lower limbs were made from a girl from 3 weeks after birth until 7 years of age to determine EMG changes in the development of human bipedal locomotion. Recordings were taken from the tibialis anterior (TA), lateral gastrocnemius (LG), vastus medialis (VM), rectus femoris (RF), biceps femoris (BF), and gluteus maximus muscles. In each of three developmental stages of gait, primitive walking, supported walking, and independent walking, muscle activity progressed from excessive co-contraction of mutual antagonists to reciprocal patterns.