Question

What does the term "motor unit recruitment" mean?

Answer 1

Motor unit recruitment refers to the activation of additional motor units to accomplish an increase in contractile strength in a muscle. A moto unit consisits of one motor neuron and all of the muscle fibers it stimulates. All muscles consist of a number of motor units and the fibers belonging to a motor unit are dispersed and intermingle amongst fiberd of other units. The muscle fibers belonging to one motor unit can be spread throughout part, or most of the entire muscle, depending on the number of fibers and size of the muscle. When a motor neuron is activated, all of the muscle fibers innervated by the motor neuron are stimulated and contract. The activation of one motor neuron will result in a weak but distributed muscle contraction.The activation of more motor neurons will result in more muscle fibers being activated, therefore a stronger muscle contraction.

Motor unit recruitment is a meassure of how many motor neurons are activated in a particular muscle, and therefore is ameassure of how many muscle fibers of that muscle are activated.