A Motor unit (MU) is the alpha motor neuron and all of the muscle fibers that it innervates (meaning the part of the nervous system that communicates with and controls the muscle fibers).
Motor units are activated based on threshold, which is a property of fiber type. Low threshold MU's (type I oxidative) are recruited fast and have lower force production capabilities. High threshold (type II gylcolytic) are typically recruited after low threshold MU's, with the exception of ballistic movements. To achieve increased power it is important that we recruit higher threshold MU's.
Why should we increase power? Because it is a key component of anaerobic performance and is highly correlated with functional capacity. (NSCA, 2008). Walking isn't a strong enough stimulus to elicit many high threshold MU's. Jumping, plyometrics, HIIT, and other explosive movements will help to create a powerful, dynamic, and well crafted form and function!