tion of guinea pig and human diaphragm. J. Appl. Physiol. 34(2): 233-237. 1973.-Our purpose was to relate the fiber composition of the diaphragm to the decline in maximum tension and in maximum voluntary ventilation (MVV) over time. In isolated guinea pig diaphragm, three fiber types were classified and three rates of fatigue observed. An initial rapid decline in tension corresponds to the area of the diaphragm composed of low oxida-tive fast-twitch (LFT) fibers and a subsequent slower rate with the percentage of high oxidative fast-twitch (HFT) fibers. The per-centage of maximum tension maintained after 20-30 min of stimulation correlates with the percentage of high oxidative slow-twitch (HST) fibers. Seven men performed MVV tests of from 15 set to 5 min duration. In tests conducted for 1 min, MVV is 82 yO of the MW after 15 sec. No further decrease occurs in tests administered for 5 min. In human diaphragm, 76( % of the fibers
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Lieberman et al. (1973) studied this question.