The purpose of training to momentary muscle fatigue is to actively recruit all of the available motor units (the nerve and the muscle fibres stimulated by that nerve) within a muscle group. The order of motor unit recruitment is dependent on the force needs placed on the muscle. The greatest force producing fibres in the human body, are known as Type IIb or Type IIx (Fast Twitch, Low Oxidative) (the ‘x’ noting there are several variations of this fiber type). It is these higher threshold fast twitch motor units, which are capable of producing the greatest increases in muscular strength and size. Type IIb or IIx muscle fibres are recruited the closer an individual gets to MMF as Type I (Slow Twitch, High Oxidative) fibres will actually recycle during the set. If muscular strength is the primary objective, it is felt that the degree of activation of motor units is directly related to the magnitude of the strength training response (Willardson, 2007).
Theory behind MMF
