Clinical assessment of skeletal muscle function

A systematic clinical analysis of skeletal muscle function is presented. Tests range from assessment of muscle weakness with a new hand-held dynamometer (the "Hammersmith Myometer") to studies of the contractile properties of the quadriceps and adductor pollicis muscles described in terms of the force generated at different frequencies of stimulation of the motor nerve, the force-sustaining capability and the time course of relaxation following a brief tetanus. A new measure of the energy-exchanging capacity of muscle is given by the Myothermogram (MTG - so named by analogy with the Electromyogram - EMG). The technique measures metabolic heat production in muscles when maximally activated by voluntary effort or electrical stimulation and the heat changes during sustained contractions. The MTG offers a practical means for assessing in normal and diseased human muscle the metabolic capacity, economy of force maintenance and fatigue mechanisms. Needle biopsy provides safe, rapid and repeatable access to muscle for diagnosis, studies of chemical energy exchange and the correlation of function and metabolism with constituent muscle fibre types. This approach provides a possible basis for recognising the functional disorder and for evaluating the effects of physiotherapy and drug treatments in patients with neuromuscular disorders.