Erceg, D. N., Schroeder, E. T., Kawakubo, M., Castaneda-Sceppa, C., Binder, E. F., Yarasheski, K. E., Bhasin, S., Sattler, F R., & Azen, S. P. (2008). The effects of IGF-1 on aerobic muscle endurance in older hyposomatotropic men. ACSM 55th Annual Meeting Indianapolis, Presentation Number, 2481.

This study assessed the hypothesis that augmenting IGF-1 levels with rhGH will be associated with improved aerobic muscular endurance in older (aged ~70 years) healthy, hyposomatotropic, community-dwelling men. Ss received rhGH at 0, 3.0, or 5.0 mg/kg/day in combination with transdermal testosterone at 5 or 10 g/day. Muscular endurance was determined by two cycle ergometer tests. First, VO2peak was assessed using a ramping protocol to volitional fatigue, and after a 30-minute rest, a second test (aerobic endurance) that measured time to failure at 80% of the max workload reached during the VO2peak test was performed. The rhGH groups were combined for statistical analyses.

The rhGH group showed a significant increase in IGF-1. All groups (placebo and rhGH) significantly improved aerobic endurance but not VO2peak. No significant correlations were determined between IGF-1 and muscular endurance measures:

Implication. The augmentation of levels of IGF-1 in older hyposomatotropic men does not result in improvements in muscular endurance. However, there may be an effect or interaction with testosterone status since aerobic endurance increased significantly in Ss whether or not they received rhGH.

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