Plasticity in the motor pathway in the spinal cord in muscle training
The corticospinal pathway is the main pathway for control of voluntary movement in humans. Its nerve cells carry signals from the motor parts of the brain to the motoneurones in the spinal cord. Firing of the motoneurones then drives the muscles. When we learn new motor skills through practice, changes in the motor area of the brain are thought to contribute to this learning. In contrast, when we train to improve muscle strength, changes may occur in the spinal cord but this is not yet clear. Increasing the strength of these connections in the spinal cord would mean that the same output from the brain would be able to engage more motoneurones, and hence, more muscle. It would be easier to make strong contractions. We propose that training for muscle strength by performing repeated strong voluntary contractions can increase the strength of the connections between the corticospinal cells and the motoneurones. A current study is examining this question for strength training of the elbow flexor muscles in healthy volunteers.