IGF-I and IGFBP-3 during continuous and interval exercise

The purpose of this research was to compare changes in circulating levels of total IGF-I and IGFBP-3 during continuous, moderate-intensity exercise (CE) and high-intensity interval exercise (IE) of equal duration. Ten healthy males completed 2 exercise sessions and a resting control session (R) in random order. The CE was 20 minutes of cycling at 60-65% of (V) over dot O-2max. During IE, subjects cycled at 80-85% of (V) over dot O-2max for 1 minute followed by 40 seconds of active recovery, with the cycle repeated for a total of 20 minutes. In each session blood samples were drawn at -10, 0, 5,10, 20 and 30 minutes. Both IGF-I and IGFBP-3 increased during exercise (p < 0.05) and repeated measures ANOVA revealed a significant effect for session (IE, CE > R, p < 0.05). Area under the curve (AUC) analyses showed no difference in IGF-I between sessions, however, the IGFBP-3 AUC was significantly greater during IE than R (p < 0.05). These results suggest interval and continuous exercise will result in similar changes in circulating IGF-I and IGFBP-3. This could be beneficial to individuals who can exercise longer and at a higher intensity in intervals than would be possible using a continuous protocol.