EFFECT OF RESISTANCE EXERCISE AND GROWTH-HORMONE ON BONE-DENSITY IN OLDER MEN

OBJECTIVE The purpose of this study was to evaluate whether 16 weeks o f heavy resistance exercise training combined with daily growth hormon e administration (GH) increases bone mineral density in 64-75-year-old men greater than resistance exercise training without GH supplementat ion. DESIGN Eighteen healthy, elderly men (67 +/- 1 year) followed a 1 6-week progressive resistance training programme (75-90% maximum stren gth, 5-10 repetitions/set, 4 sets/day, 4 days/week) after double-blind , random assignment to either a GH (12.5 or 18 mu g/kg/day, equivalent to 25 or 36 mU/kg/day, n=7) or placebo (n=11) group, MEASUREMENTS Bef ore and at the end of 16 weeks of resistance exercise with or without GH administration, body composition, whole body and regional bone mine ral density (BMD) were determined by dual-energy X-ray absorptiometry. Serum osteocalcin and IGF-I were determined by radioimmunoassay befor e, during and at the end of treatment, RESULTS Increments in fat-free mass and training-specific maximum voluntary muscle strength were simi lar in both groups after training, Serum insulinlike growth factor-I ( IGF-I) and osteocalcin levels were increased (P<0.05) after exercise t raining plus GH, In comparison to initial measures, bone mineral densi ty (g/cm(2)) of the proximal femur (Ward's triangle) was increased (P< 0.05) after 16 weeks of exercise training plus placebo treatment, Sixt een weeks of exercise training plus GH treatment did not increase whol e body, spine or hip (femoral neck, trochanter, Ward's triangle) bone mineral density more than exercise plus placebo treatment, CONCLUSIONS These findings suggest that in these older men with normal bone miner al density, shortterm resistance exercise training increased regional bone mineral density, but the addition of daily GH administration did not enhance whole body or regional bone mineral density despite GH-ind uced increments in serum IGF-I and osteocalcin. This implies that GH a dministration during a IS-week resistance exercise training programme may increase bone turnover without increasing bone mineral accumulatio n.