High-Intensity Interval or Continuous Moderate Exercise: A 24-Week Pilot Trial

PURPOSE: High-intensity interval training (HIIT) may lead to superior cardiometabolic improvements when compared with moderate-intensity continuous training (MICT). However, adherence to HIIT requires examination. The purpose of this pilot study was to examine moderate-to-vigorous physical activity (MVPA) adherence 24 wk after a brief counseling intervention combined with either HIIT or MICT. METHODS: Individuals at high risk of type 2 diabetes (T2D) were randomized to HIIT (n = 15) or MICT (n = 17) and completed 10 exercise sessions accompanied by a brief 10-min counseling intervention over a 2-wk period. Objectively measured purposeful MVPA (accelerometry) and cardiorespiratory fitness (V˙O2peak) were assessed at baseline and 24 wk postintervention. Self-regulatory efficacy and task self-efficacy were examined at baseline, postintervention, and 24 wk postintervention. Using an intention-to-treat analysis, change scores were calculated for HIIT and MICT and compared between groups. RESULTS: Individuals assigned to HIIT increased their MVPA by 53 min (Cohen's d = 1.52) at 24 wk compared with 19 min in MICT. Both HIIT and MICT increased relative V˙O2peak by 2 and 1 mL·kg·min, respectively. Participants in both groups increased in their self-regulatory and task self-efficacy postintervention, but both groups demonstrated similar decline at 24 wk. CONCLUSION: This pilot intervention was successful in increasing, and maintaining, free-living MVPA over a 24-wk period in individuals at high risk of T2D. Speculation that HIIT is inappropriate or unattainable for overweight individuals at high risk of T2D may be unfounded.