Our results are encouraging in that they suggest an effect of growth hormone on a specific aging-correlated deficit. IGF-I was increased by administrating rhGH and muscle strength was increased by exercise. The administration of rhGH to frail older individuals in this study resulted in significant changes in the proportions of fiber types. Whether changes in fiber cross-sectional area or absolute number occur with long-term growth hormone administration requires further study.

The percutaneous muscle biopsy technique is used in clinical practice and biomedical research. We developed a new enhanced-suction technique [suction-enhancing nipples (SEN)] and compared it with techniques currently in practice by assessing biopsy yields on anesthetized pigs. We applied the enhanced-suction technique to human subjects participating in a clinical trial. In the pig, there was a mean 91% (1.9-fold) increase in the size of the samples obtained with the 4-mm needle when SEN was used and a mean 507% (fivefold) increase in sample size when the SEN was applied to the 6-mm needles. Nine passes of the 6-mm needle with SEN obtained from five consecutive human subjects yielded a mean individual sample size of 109.4 mg or 219.4 mg per needle pass when using the double-sample technique. Adequate tissue samples for histomorphometric and other analyses were obtained in all samples obtained. The percutaneous muscle biopsy performed with enhanced suction using inexpensive, readily available nipples enhances tissue yield two- to fivefold.