Growth hormone and insulin-like growth factor 1 responses to acute resistance exercise in untrained women

While serum growth hormone (GH) increases with exercise have been consistently observed, serum insulin-like growth factor 1 (IGF-1) responses have been equivocal. In addition, little is known about IGF-1 responses in women after acute resistance exercise. The purpose of this study was to examine serum GH, IGF-1 and lactate responses to an acute resistance exercise protocol (RE) among 47 women (22±3 yr.; 165±6 cm; 62±8 kg; 25±5 %BF). Venous blood was obtained from subjects via pre- and post-RE (6 sets of 10RM squats separated by 2 min). Serum GH and IGF-1 concentrations were then determined by radioimmunoassay. The RE resulted in significant (p≤05) increases in lactate (2.1±.8 vs. 10.4±3.2 mmol/L) and GH (4.9±6.3 vs. 16.6±8.8 μg/L), but not in IGF-1 (36.4±9 vs. 38.0+.8.4 nmol/L). Individual IGF-1 responses, however, were highly variable with changes ranging from -40% to +49%. Tenues based on these %Δs in IGF-1 revealed a 13±9% decrease (40.8±10 vs. 35.0±6 nmol/L) in tertile 1 and a 27±10% increase (31.0±8 vs. 39.6±10 nmol/L) in tertile 3; pre-IGF-1 values between these tertiles also differed. IGF-1 %Δs were not correlated with pre-exercise GH or %ΔGH values but were negatively correlated with pre-exercise IGF-1 values (r=-.51). These data confirm the independence of IGF-1 exercise responses from immunoreacrive GH, and also suggest that pre-exercise values of IGF-1 may be a factor associated with the potential IGF-1 response to exercise in women.