Differences in flexor and extensor activity during locomotor-related leg movements in chick embryos

Area of Science:

• Neuroscience
• Developmental Biology
• Biomechanics

Background:

• Chick embryos exhibit repetitive limb movements (RLMs) prior to hatching, which are considered a precursor to walking.
• RLMs involve alternating flexor and extensor muscle activity, mirroring gait phases.
• Previous research noted inconsistent extensor muscle recruitment during RLMs.

Purpose of the Study:

• To investigate if flexor muscles are preferentially recruited during RLMs in chick embryos one day before hatching.
• To compare electromyography (EMG) burst parameters between flexor and extensor muscles at the hip and ankle during RLMs.

Main Methods:

• Utilized a within-subject design to analyze EMG data from chick embryos.
• Compared burst count and neural drive parameters for hip and ankle flexor and extensor muscles during RLMs.

Main Results:

• Flexor muscles exhibited a higher burst count compared to extensor muscles.
• Flexor muscles were consistently recruited at lower levels of neural drive.
• A significant bias favoring flexor muscle recruitment and drive was observed during RLMs.

Conclusions:

• Spontaneously produced RLMs in late-stage chick embryos demonstrate a preferential bias for flexor muscle activation and drive.
• This finding offers insights into the neural mechanisms and developmental implications of early motor pattern generation.
• The observed flexor bias may influence the development of coordinated gait patterns.