Skeletal muscle fiber composition, nutritional status and subjective fatigue during surgical convalescence.

Samples from the lateral vastus femoris muscle were obtained by needle biopsy from 12 patients before and 20 days after elective abdominal surgery. The content of fast and slow twitch muscle fibers and their lesser diameter were determined and related to subjective degree of fatigue and changes in nutritional parameters. Fatigue increased from a mean preoperative level of 2.2 +/- 0.4 arbitrary units to 4.3 +/- 0.5 (p less than 0.001) on postoperative day 20. Body weight, triceps skin fold and slow twitch fiber diameter decreased postoperatively (p less than 0.05). There was no significant postoperative change in the distribution of muscle fiber types. Fatigue increase correlated to weight loss and reduction of triceps skin fold (r = 0.50 and 0.54, p = 0.08 and 0.06, respectively). Postoperative changes in slow and fast twitch fiber diameter correlated to loss of body weight (r = 0.60 and 0.74, p less than 0.05 and less than 0.01, respectively), but correlation was not found between postoperative fatigue and changes in fiber-type distribution (r = 0.34 and 0.29).