Abstract

Physiologic methods have been developed to objectively quantify muscle strength, endurance, and fatigability. Isometric force and rectified/integrated electromyogram were simultaneously recorded during the three phases of a recording session: (I) pre-fatigue, (II) fatigue (1 min duration) and (III) post-fatigue recovery (up to 10 min). Five parameters of muscle performance were computed: (1) Maximum force (MF) exerted during isometric voluntary contraction (muscle strength); (2) Force-time integral-area under force-time plot (endurance); (3) Fatigue index (FI) ( reduction in MF); (4) Neuromuscular efficiency (force/m V of EMG recruited), and (5) Recovery time (RT). Normal values based on data from 20 normal subjects were determined for four muscles: index finger abductor, elbow flexors, knee extensors, and ankle dorsiflexors. Neuromuscular efficiency (NME) decreased significantly (20 to 70) at the end of the fatigue phase; it generally increased to the pre-fatigue level in 2 to 10 min, during the recovery phase. The period needed to reach pre-fatigue level was referred to as RT. The elbow flexors had the highest mean FI (48) and the longest RT (>6min); the ankle dorsiflexors had the lowest mean FI (34) and the shortest RT (1.5min). These methods have been used also to evaluate the effects of weight training in two patients with neuromuscular disorders. Verf.-Referat