2 YEARS OF GROWTH-HORMONE (GH) TREATMENT INCREASE ISOMETRIC AND ISOKINETIC MUSCLE STRENGTH IN GH-DEFICIENT ADULTS

GH deficiency in adults is associated with reduced muscle mass and mus cle strength. The objective of this trial was to follow the effect of 2 yr of GH treatment in GH-deficient adults on muscle performance in r elation to a reference population. Knee extensor and flexor strengths for isometric and isokinetic concentric muscle strength were measured using a Kin-Com dynamometer. Hand-grip strength was measured in both h ands. The fatigue index was calculated as the percent reduction in pea k torque at 50 repeated isokinetic knee extensions. Superimposed, sing le twitch electrical stimulation was performed. The GH-deficient subje cts had lower isometric knee extensor, knee flexor, and hand-grip stre ngth than the reference population. Two years of GH treatment increase d and normalized the mean isometric knee extensor and flexor strengths . The concentric knee flexor and extensor strength at an angular veloc ity of pi rad/s increased, as did the concentric knee flexor strength at an angular velocity of pi/3 rad/s. The increase in muscle strength was more-marked in younger patients and in patients with lower initial muscle strength than predicted. Quadriceps endurance decreased, where as the effect of superimposing single twitches on isometric contractio n and hand-grip strength was unaffected by the GH treatment. Two years of GH therapy in GH-deficient adults increased and normalized isokine tic and isometric muscle strength studied in proximal muscle groups. H and-grip strength and the degree of lack of maximal motor unit activat ion on voluntary isometric knee extensor force did not change. The dyn amic local muscle fatigue index decreased.