QUANTIFYING HUMAN-MUSCLE STRENGTH, ENDURANCE AND FATIGUE

  • 1 August 1986
    • journal article
    • research article
    • Vol. 67  (8) , 530-535
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/mV 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 flexor, 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 (> 6 min); the ankle dorsiflexors had the lowest mean FI (34%) and the shortest RT (1.5 min). These methods have been used also to evaluate the effects of weight training in two patients with neuromuscular disorders.