Comparison of high-intensity interval training protocol designs on accumulated time ≥ 90% V̇O₂max: a network meta-analysis.
Level 1 - systematic review of randomized trials
Systematic review and network meta-analysis of controlled trials
PubMed 42482078 · doi:10.1186/s13102-026-01891-7
What was done
Authors conducted a systematic review and frequentist random-effects network meta-analysis searching PubMed, Web of Science, and SPORTDiscus through January 31, 2026. They included controlled studies evaluating different high-intensity interval training (HIIT) protocol structures on accumulated time ≥ 90% of maximal oxygen uptake (V̇O₂max) in healthy athletes. Protocols were categorized by interval duration, work-to-rest structure, intensity pattern, and within-session progression, using even long intervals as the reference comparator.
What was found
Across 19 publications (20 study units, n = 240 athletes, mean age 25.5 ± 5.3 years, baseline V̇O₂max 60.5 ± 8.1 ml·kg⁻¹·min⁻¹), no HIIT protocol structure differed significantly from even long intervals in accumulated time ≥ 90% V̇O₂max. Point estimates compared to even long intervals were highest for decreased-duration (SMD = 0.87, 95% CI -0.30 to 2.04) and varied-intensity protocols (SMD = 0.54, 95% CI -0.42 to 1.49), and lowest for 1:1 blocks (SMD = -0.68, 95% CI -1.40 to 0.04). P-score ranking favored decreased-duration (89.6%), varied-intensity (76.7%), and decreased-intensity (68.4%), while 1:1 blocks ranked lowest (2.8%). The network exhibited substantial heterogeneity and significant inconsistency (I² = 69.2%, 95% CI 49.9% to 81.0%; total Q = 55.12, p < 0.0001; between-design Q = 20.78, p = 0.002).
Why it matters
Despite theoretical advantages proposed for novel HIIT configurations, current evidence does not demonstrate superiority of any specific interval structure over standard long intervals for maximizing time spent at high aerobic intensities. Training prescription should prioritize practical feasibility and individual workload matching rather than complex protocol adjustments.
Limits
The network displayed significant statistical inconsistency and substantial heterogeneity (I² = 69.2%), with sparse data across several comparison nodes. All confidence intervals around standardized mean differences crossed zero. The total sample was modest (240 participants across 20 study units) and limited to healthy, well-trained athletes, precluding generalization to sedentary or clinical populations.
Cited by
- context The optimal interval duration for generating VO2 max adaptation is 3 to 8 minutes with a 1:1 work-to-recovery ratio.