LOSS OF MUSCLE MASS IS POORLY REFLECTED IN GRIP STRENGTH PERFORMANCE IN HEALTHY-YOUNG MEN

Isometric maximal handgrip strength (GS(max)) has been used as an expedient test of overall muscle strength and index of fat-free mass (FFM). We tested this relationship in 55 fit young men undergoing high rates of FFM loss in an 8.5-wk military training course involving multiple stressors including nutritionally uncomplicated energy deficit. GS(max) was measured by a hand dynamometer interfaced with a computer providing visual feedback; another strength test, measuring dynamic strength of larger muscle groups (Clean(sim)), was also performed. GS(max) did not change (530 +/- 57 vs 529 +/- 63 N) in the face of a 15.6% loss of body weight (12.1 +/- 3.4 (SD) kg), including 6.9% loss of FFM (4.6 +/- 2.6 kg), but Clean(sim) decremented significantly (77.4 +/- 9.6 to 58.7 +/- 8.9 kg) and changes were significantly correlated with Delta FFM for GS(max) (r = 0.31) and Clean(sim) (r = 0.49). We conclude that GS(max) is not a good representation of changes in total FFM in healthy young men even though it appears to be useful in more severely catabolic patients with extreme losses of FFM and in pubertal boys making large gains in FFM. Other aspects of physical performance are clearly affected by high rates of weight loss, as demonstrated by decrements in the Clean(sim) and its stronger relationship to Delta FFM.