Skeletal muscle function in malnutrition

Abstract

Skeletal muscle function was studied in 10 malnourished patients with various gastrointestinal disorders and in 22 normal subjects. The function of the adductor pollicis muscle was assessed by electrical stimulation of the ulnar nerve. The objective parameters of muscle function measured were: 1) Force of contraction expressed as a percentage of the maximal force obtained with electrical stimulation at 10, 20, 30, 50 and 100 Hz. 2) Maximal relaxation rate expressed as percentage force loss/10 ms. 3) Endurance expressed as percentage force loss/30 s. The force of contraction at 10 Hz was higher in malnourished patients compared with normal subjects, with a mean ± SEM (n) of 43.0 ± 4.2% (n = 10) and 28.8 ± 1.2% (n = 22), respectively, (p < 0.001). The maximal relaxation rate was slower in patients compared with normals with a mean ± SEM (n) of 7.2 ± 0.4% (n = 9) and 9.6 ± 0.2% (n = 22), respectively, (p < 0.001). Muscle endurance testing showed an increased force loss with prolonged tetanic stimulation in patients compared with normals, with a mean ± SEM (n) of 29.1 ± 4.0% (n = 7) and 3.5 ± 0.8% (n = 22), respectively, (p < 0.001). Four patients were restudied after a 4-wk period of total parenteral nutrition, with a significant improvement in muscle function parameters. Malnutrition results in both increased muscle fatiguability and an altered pattern of muscle contraction and relaxation which are reversible by nutritional supplementation. This technique promises to be valuable in assessing the functional effects of malnutrition and the response to nutritional support.