SERUM [IGF-1] RESPONSE TO RESISTANCE TRAINING IS SEX DEPENDENT

Abstract

1296 Previously we presented evidence that both 3- and 6-months of 1-set and 3-set resistance training (RT) similarly and significantly increased the serum concentration of insulin-like growth factor-1 (IGF-1). Others have suggested that an acute bout of RT is accompanied by a small increase in serum [IGF-1] only in males, but it is unknown whether chronic RT has a sex dependent effect on serum [IGF-1]. In this study we compared serum [IGF-1] in females and males before and after 3-months RT. Female (n=9) and male (n=13) volunteers (age 39±6 yr) trained 3 d/wk and were randomized to either low volume (1-set per exercise) or high volume (3-sets per exercise) RT using 7 exercises of 8-12 reps to fatigue. Blood was drawn at training wk 0 and 13, and volunteers did not perform RT or other vigorous activity ≥24 h prior to sampling. IGF-1 was measured by radioimmunoassay. Males had significantly (p<0.05) increased serum [IGF-1] at RT wk 13, but females showed only a trend (p<0.08) toward increased serum [IGF-1] (Table). The 1-set compared to 3-set RT volume did not affect (p>0.05) the magnitude of increase in serum [IGF-1], for either sex. The magnitude of change in serum [IGF-1] was more than twice as great in the males compared to females (13% vs 31%, respectively). We conclude that 13 wk RT significantly increases resting, serum [IGF-1] in males, but not in females. This parallels prior observations of a blunted IGF-1 response to acute RT in females.Table