Serum levels of Insulin-like growth factor-1 (IGF-I) as an indicator associated with aerobic and anaerobic fitness assessment in adolescent boys

Background: Insulin-like growth factor -1 (IGF-I) has a variety of roles, But the abundance of scientific evidence indicates that it is a metabolic biomarker associated with indicators of physical fitness and health. The present study examined the relationship between serum levels of IGF-I and aerobic fitness, anaerobic capacity and body fat percent, systolic, and diastolic blood pressure before and after the eight weeks of high intensity intermittent training (HIIT) in adolescent boys.

Methods: In this experimental study, 22 adolescent boys in a randomly and double-blinded design were allocated in two equal groups: HIIT group (N=11) and control group (N=11). Training programs were conducted 3-4 times per week for 8 weeks. The HIIT program consisted of 6-8 running sprints (30-60 seconds) with a 3.5-4 min recovery. Mentioned indicators assessments were performed 18-24 hours pre and post intervention.

Results: IGF-1, Maximum Oxygen uptake (VO2max(, Peak Power Output (PPO) and mean power output (MPO) were significantly higher after 8 week HIIT than the pre-exercise training evaluations (P<0.001). Fatigue index and body fat percent decreased in HIIT trial after 8 week HIIT (P<0.001). Also, there was a significant positive correlation between IGF-I changes and aerobic fitness, anaerobic and body fat percentage. However, Systolic and diastolic blood pressure did not change significantly after the training period (P > 0.05).

Conclusion: The IGF-I can be used as an indicator to assess the fitness of adolescent boys.