The relationship between aerobic exercise capacity and circulating IGF-1 levels in healthy men and women.

OBJECTIVES: To determine whether aerobic capacity is associated independently with insulin-like growth factor-I (IGF-1) levels in healthy community-dwelling men and women.

SETTING: The Baltimore Longitudinal Study on Aging (BLSA).

DESIGN: A cross-sectional analysis of data from the population-based cohort of the Baltimore Longitudinal Study of Aging (BLSA).

PARTICIPANTS: We studied 181 men and 92 women aged 20 to 93 years, volunteers in the Baltimore Longitudinal Study on Aging (BLSA). Subjects were free of endocrine, renal, hepatic, gastrointestinal, or cardiac diseases, and they were taking no medications known to interfere with the growth hormone-IGF-1 axis.

MEASUREMENTS: All subjects underwent a single measurement of serum IGF-1 in the fasting state, as well as peak VO2 determinations during maximal treadmill exercise testing performed within one visit of the IGF-1 determination. Dual energy X-ray absorptiometry (DEXA) scans were performed in a subset of 171 subjects (64 women and 107 men) for determination of fat free mass (FFM).

RESULTS: In the pooled group of women and men, univariate regression analysis revealed that age was correlated strongly with decreasing IGF-1 levels (r = -0.53, P < .001) and with peak VO2r = -0.56, P < .001). IGF-1 levels were also significantly correlated with peak VO2 (r = 0.29, P < .001). There were no significant gender-related differences in these relationships. On multivariate analysis, age (beta = -0.54, P < .001), but not peak VO2 (P = -0.01, P = .840), remained strongly associated with IGF-1 levels. After adjustment of peak VO2 for FFM in subjects with DEXA scans, results were similar.

CONCLUSIONS: These findings indicate that although both peak aerobic capacity and circulating IGF-1 levels decline with age, aerobic capacity is not independently related to circulating IGF-1 in healthy men and women across the adult life span.