Childhood development of common drive to a human leg muscle during ankle dorsiflexion and gait

TY - JOUR

T1 - Childhood development of common drive to a human leg muscle during ankle dorsiflexion and gait

AU - Hvass Petersen, Tue

AU - Kliim-Due, Mette

AU - Farmer, Simon F.

AU - Nielsen, Jens Bo

N1 - CURIS 2010 5200 114

PY - 2010/11

Y1 - 2010/11

N2 - Corticospinal drive has been shown to contribute significantly to the control of walking in adult human subjects. It is unknown to what extent functional change in this drive is important for maturation of gait in children. In adults, populations of motor units within a muscle show synchronized discharges during walking with pronounced coherence in the 15-50 Hz frequency band. This coherence has been shown to depend on cortical drive. Here, we investigated how this coherence changes with development. Forty-four healthy children aged 4-15 years participated in the study. Electromyographic activity (EMG) was recorded from pairs of electrodes placed over the right tibialis anterior (TA) muscle during static dorsiflexion and during walking on a treadmill (speed from 1.8 to 4.8 km h-1). A significant increase of coherence with increasing age was found in the 30-45 Hz frequency band (gamma) during walking and during static ankle dorsiflexion. A significant correlation with age was also found in the 15-25 Hz frequency band (beta) during static foot dorsiflexion. χ2 analysis of differences of coherence between different age groups of children (4-6, 7-9, 10-12 and 13-15 years of age) revealed a significantly lower coherence in the gamma band for recordings during walking in children aged 4-6 years as compared to older children. Recordings during static dorsiflexion revealed significant differences in both the beta and gamma bands for children in the 4-6 and 7-9 years age groups as compared to the older age groups. A significant age-related decrease in step-to-step variability of toe position during the swing phase of walking was observed. This reduction in the step-to-step variability of gait was correlated with increased gamma band coherence during walking. We argue that this may reflect an increased ability to precisely control the ankle joint position with age, which may be contingent on maturation of corticospinal control of the foot dorsiflexor muscles. During childhood the human nervous system undergoes functional as well as structural changes. Such changes are responsible for the development of mature gait, which for the average child is seen around the age of 12 years. In this study we investigated healthy children aged 4-15 years during treadmill walking and found an increased synchronization of the input to spinal motoneurones that control the tibialis anterior muscle. We argue that this increased synchronization may be used as a marker of maturation of neural connections from the motor cortex to the spinal motoneurones. Precise control of the tibialis anterior muscle is necessary to safely lift the foot over the ground during the swing phase and to place it precisely on the ground in the early stance phase during walking. We observed a developmental decrease in the step-to-step variability in this control that could be related to the above described changes in synchronization. We therefore suggest that changes in the synchronous cortical drive to the spinal motoneurones may be responsible for the observed maturation of gait parameters.

AB - Corticospinal drive has been shown to contribute significantly to the control of walking in adult human subjects. It is unknown to what extent functional change in this drive is important for maturation of gait in children. In adults, populations of motor units within a muscle show synchronized discharges during walking with pronounced coherence in the 15-50 Hz frequency band. This coherence has been shown to depend on cortical drive. Here, we investigated how this coherence changes with development. Forty-four healthy children aged 4-15 years participated in the study. Electromyographic activity (EMG) was recorded from pairs of electrodes placed over the right tibialis anterior (TA) muscle during static dorsiflexion and during walking on a treadmill (speed from 1.8 to 4.8 km h-1). A significant increase of coherence with increasing age was found in the 30-45 Hz frequency band (gamma) during walking and during static ankle dorsiflexion. A significant correlation with age was also found in the 15-25 Hz frequency band (beta) during static foot dorsiflexion. χ2 analysis of differences of coherence between different age groups of children (4-6, 7-9, 10-12 and 13-15 years of age) revealed a significantly lower coherence in the gamma band for recordings during walking in children aged 4-6 years as compared to older children. Recordings during static dorsiflexion revealed significant differences in both the beta and gamma bands for children in the 4-6 and 7-9 years age groups as compared to the older age groups. A significant age-related decrease in step-to-step variability of toe position during the swing phase of walking was observed. This reduction in the step-to-step variability of gait was correlated with increased gamma band coherence during walking. We argue that this may reflect an increased ability to precisely control the ankle joint position with age, which may be contingent on maturation of corticospinal control of the foot dorsiflexor muscles. During childhood the human nervous system undergoes functional as well as structural changes. Such changes are responsible for the development of mature gait, which for the average child is seen around the age of 12 years. In this study we investigated healthy children aged 4-15 years during treadmill walking and found an increased synchronization of the input to spinal motoneurones that control the tibialis anterior muscle. We argue that this increased synchronization may be used as a marker of maturation of neural connections from the motor cortex to the spinal motoneurones. Precise control of the tibialis anterior muscle is necessary to safely lift the foot over the ground during the swing phase and to place it precisely on the ground in the early stance phase during walking. We observed a developmental decrease in the step-to-step variability in this control that could be related to the above described changes in synchronization. We therefore suggest that changes in the synchronous cortical drive to the spinal motoneurones may be responsible for the observed maturation of gait parameters.

U2 - 10.1113/jphysiol.2010.195735

DO - 10.1113/jphysiol.2010.195735

M3 - Journal article

C2 - 20837641

SN - 0022-3751

VL - 588

SP - 4387

EP - 4400

JO - The Journal of Physiology

JF - The Journal of Physiology

IS - 22

ER -