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. For the stance limb, the predominant reciprocal pattern to emerge was continuous activity of the posteriorly located LG and BF as opposed to the anteriorly located TA and RF. In independent walking this preponderance of maintained activity by the LG and BF in stance phase gradually waned over the first 2 years of walking to focused bursts of activity. The developmental changes observed in this girl appear to have been attributable to changes in posture reflecting increased strength and to improvements in control of balance reflecting neuromaturation.