Critique of Papers by Awiszus & Feistner; Cope & Clark; Durkovic; Windhorst; Kouchtir, Perrier, Zytnicki & Jami

Abstract

The discussion on recruitment order has been much dominated by Henneman’s’ size principle’. With our present understanding this hypothesis implies that the major factors determining the recruitment order are localised to the motoneurones themselves. That may be the sum of several mechanisms (such as membrane resistivity, threshold levels etc.) which are correlated to motoneuronal size. In addition to these properties of the motoneurones themselves, it is obvious that the distribution of the synaptic input in the motoneuronal pool must also play a role. The predominant projection of Ia excitation to slow motor units — rather than to fast units — surely contributes to reinforce and conserve the normal recruitment order.