Changes in the Fitness Fatness Index following reduced exertion high-intensity interval training versus moderate-intensity continuous training in physically inactive adults.
Level 2 - randomized trial
Individual randomized controlled trial
PubMed 35992158 · doi:10.3389/fspor.2022.961957
What was done
Thirty-two physically inactive adults were randomized into an 8-week exercise intervention: reduced exertion high-intensity interval training (REHIT, n = 16) or moderate-intensity continuous training (MICT, n = 16). REHIT participants performed 10 minutes of individualized cycling intervals 2 to 4 days per week, while MICT participants performed aerobic exercise at 50% to 65% of heart rate reserve 3 to 5 days per week. The Fitness Fatness Index (FFI), defined as cardiorespiratory fitness (in metabolic equivalents) divided by waist-to-height ratio, was measured at baseline and at 8 weeks. A 1-unit increase was defined as clinically significant.
What was found
The REHIT group showed a significantly greater increase in FFI (+1.95 ± 0.63) than the MICT group (+0.99 ± 0.47; between-group difference, p < 0.001). A significantly higher proportion of participants in the REHIT group achieved a clinically significant increase in FFI (12/12, 100%) compared to the MICT group (8/15, 53%; between-group difference, p = 0.01).
Why it matters
This study shows that a brief 10-minute interval exercise protocol can be more effective at improving a composite cardiovascular risk marker than traditional continuous moderate exercise in inactive adults.
Limits
The study had a very small sample size (32 randomized, with 5 dropouts evident in the analysis). The abstract does not report participant demographics such as age and sex, exercise adherence rates, or hard cardiovascular disease outcomes beyond the surrogate index.
Cited by
- supports An 8-week clinical trial comparing REHIT against 30-minute moderate exercise sessions found that 100% of REHIT participants achieved clinically significant improvements on the fitness-fatness index, compared to 53% in the moderate exercise group.