Acute Exercise and Insulin Sensitivity in Boys: A Time-Course Study.

Area of Science:

• Exercise Physiology
• Metabolic Health
• Adolescent Health

Background:

• Understanding the acute effects of different exercise intensities on insulin sensitivity is crucial for metabolic health in adolescents.
• Previous research has explored exercise-induced adaptations, but the time course of these changes, particularly after high-intensity interval exercise (HIIE) versus moderate-intensity exercise (MIE), requires further investigation in this demographic.

Purpose of the Study:

• To examine the time course of adaptations in insulin sensitivity (IS) in adolescent boys following acute high-intensity interval exercise (HIIE) and moderate-intensity exercise (MIE).
• To compare the effects of HIIE and MIE on IS using both fasted (HOMA) and post-oral glucose tolerance test (OGTT) measures.

Main Methods:

• Eight adolescent boys (15.1±0.4 years) participated in a randomized crossover trial involving three conditions: HIIE, MIE, and a rest control (CON).
• Insulin sensitivity was assessed using the HOMA index from fasted blood samples and the Cederholm index from OGTT measurements at multiple time points (POST-Ex, 24h-POST, 48h-POST).
• HIIE involved 8x1-minute cycling bursts at 90% peak power with 75-second recovery; MIE matched HIIE work duration at 90% of gas exchange threshold.

Main Results:

• Insulin sensitivity, assessed via OGTT, was significantly higher immediately post-exercise (POST-EX) following HIIE compared to CON (17.4% increase).
• A non-significant trend for increased IS was observed after MIE compared to CON (9.0% increase).
• At 24 hours post-exercise (24h-POST), IS remained significantly elevated compared to CON following both HIIE (13.2% increase) and MIE (9.7% increase).

Conclusions:

• A single bout of either HIIE or MIE can acutely enhance insulin sensitivity in adolescent boys.
• The improvements in insulin sensitivity following both exercise modalities persist for at least 24 hours post-exercise when measured using the OGTT.
• These findings highlight the potential of different exercise intensities to positively impact metabolic health in young males.