Exercise-induced Changes In DHEA And IGF-I In Overweight And Normal Weight Women Of Varying Age

There is evidence that circulating concentrations of insulin-like growth factor-I (IGF-I) and DHEA are related to both age and body mass index (BMI). It is not clear how these factors will affect DHEA and IGF-I responses to acute physical exercise. PURPOSE To compare circulating levels of DHEA and IGF-I before and after resistance exercise in normal weight and overweight women of varying age. METHODS Volunteer participants were 29 women who were not regularly resistance training and not taking any hormone therapy or contraceptives. They were divided into4groups: older and normal weight (ONW) (n=8, BMI=23.2± 1.1, age=52.5±6.9), younger and NW (YNW) (n=7, BMI=21.6±1.9, age=25.6±2.4), older and over weight (OOW) (n=8, BMI=32.4±5.4, age=54±3.4), and younger and over weight (YOW) (n=6, BMI=31.4±3.3, age=25.3±3.1). Participants were screened and completed a fitness appraisal and a familiarization session. The experimental session consisted of 2 sets of 8 exercises at 10RM intensity. Pre-exercise (sample 1), post-exercise (sample 2) and 15 minute recovery (sample 3) blood samples were analyzed for plasma lactate and serum levels of IGF-I and DHEA. Group and time comparisons were made using ANOVA. RESULTS The pre-exercise concentration of DHEA was significantly greater in YOW than all other groups (p<.01) while there was no group difference in pre-exercise IGF-I levels. Post-exercise change in lactate was not significantly different between groups. When IGF-I was analyzed as either the absolute or relative post-exercise change, there was a significant main effect for group (YNW >OOW, p sample 1, p<0.05). A regression analysis revealed that the relative post-exercise change in IGF-I was significantly inversely related to BMI (r = −.49, p<0.01). There were no significant group or time effects for DHEA, however the absolute and relative post-exercise change in DHEA was significantly related to post-exercise change in lactate (r =.56, p<.01). CONCLUSION Despite high variability, these preliminary data suggest that increasing BMI is associated with a reduced IGF-I response to exercise, regardless of age. This could have negative implications for musculoskeletal training adaptations in overweight women.