Muscle fiber type characteristics of M. deltoideus in wheelchair athletes. Comparison with other trained athletes.

Muscle biopsies were obtained from the midportion of m. deltoideus of seven male wheelchair basketball athletes. High caliber kayak paddlers (n = 8) and wrestlers (n = 8) as well as mountain ranger soldiers (n = 8) served as controls. Histochemical methods were applied to identify fast twitch (FT) and slow twitch (ST) fibers and furthermore assess muscle fiber type distribution and muscle fiber cross-sectional area. The relative percentage of FT fibers averaged (+/-SD) 47 +/- 12% and 52 +/- 9% in wheelchair athletes and soldiers. The value obtained in kayakers was significantly lower (30 +/- 11). Both FT area (p less than 0.01) and mean fiber area (p less than 0.05) were significantly larger in wheelchair athletes as compared with soldiers and kayakers. It is suggested that the involvement in specific physical training was the main cause for hypertrophy of individual muscle fibers observed in m. deltoideus of wheelchair athletes.