Effects of sprint interval training on metabolic flexibility in adults living with and without obesity

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University of New Brunswick
BACKGROUND: Exercise training has been shown to improve impaired metabolic flexibility in individuals living with obesity. However, there is limited research on sprint interval training (SIT) and metabolic flexibility, and its association with clinical health outcomes such as insulin sensitivity. OBJECTIVES: The primary objective was to compare chronic and acute changes in metabolic flexibility for individuals living with or without obesity following a four-week SIT intervention. The secondary objective was to investigate if change in metabolic flexibility was associated with changes in insulin sensitivity. METHODS: A total of 34 adults living with obesity (BMI ≥ 30 kg/m2; n=16) or without obesity (BMI < 25 kg/m2; n=18) were recruited and took part in a 4-week SIT intervention performed three times per week. Each exercise session was composed of intervals of a 30 seconds Wingate using 7.5% of the participant’s body weight as the load and was separated by four minutes of active recovery performed at 59 watts. Chronic and acute metabolic flexibility were measured using VCO2/VO2 pre and post session and intervention. Change in insulin sensitivity was measured using the Matsuda index estimated from an oral glucose tolerance test. RESULTS: A significant interaction effect (group x time) was observed for acute metabolic flexibility [F(1,31)=14.55, p=0.001] and insulin sensitivity [F(1,31)=5.010, p=0.033]; however, no significant interaction was observed for chronic metabolic flexibility (p>0.05). No significant correlations were observed between changes in metabolic flexibility (chronic and acute) and changes in insulin sensitivity (p>0.05). CONCLUSION: Individuals living with obesity improved acute metabolic flexibility and insulin sensitivity over time with only four weeks of SIT. More mechanistic studies with larger sample size are needed to better understand how changes in metabolic flexibility and insulin sensitivity are modified with short-term SIT.