Resistance training in the oldest old: consequences for muscle strength, fiber types, fiber size, and MHC isoforms.

Resistance training-related changes in muscle strength, muscle size, fiber type, and myosin heavy chain isoform composition in 11 elderly subjects (age range, 85-97 years) after 12 weeks of heavy resistance training (80% of 1 RM) were examined. Twelve subjects constituted a control group. Resistance training increased isometric knee extensor strength 37% (P<0.05) and isokinetic knee strength 41-47% (P<0.05). Lean-quadriceps cross-sectional area increased 9.8% (P<0.05). Muscle fiber hypertrophy occurred only in the type 2 fibers (22% (P<0.05)). Type 1 fiber-type area percentage decreased [4.0 % (P<0.05)] whereas fiber-type area percentage of type 2a fibers increased [5.9% (P<0.05)]. The relative amount of myosin heavy chain (MHC) I (P<0.05) decreased and the relative amount of MHC IIA increased (P<0.05). No effects in the overall number of capillaries per area was observed, but an increase in the number of capillary contacts in the type 2 fiber pool was observed. Heavy resistance training does have beneficial effects on muscle strength and muscle volume in very old frail humans. Furthermore, an increase in fiber size of the fast muscle fibers and an overall increase in the relative amount of fast MHC IIA can lead not only to a stronger, but maybe more importantly, to a more powerful skeletal muscle.