Twelve Weeks of Sprint Interval Training Improves Indices of Cardiometabolic Health Similar to Traditional Endurance Training despite a Five-Fold Lower Exercise Volume and Time Commitment.
Level 2 - randomized trial
Controlled exercise training trial with parallel intervention and control groups.
PubMed 27115137 · doi:10.1371/journal.pone.0154075
What was done
Sedentary men (mean age 27±8 years, BMI 26±6 kg/m²) completed 12 weeks (3 sessions/week) of sprint interval training (SIT, n=9), moderate-intensity continuous training (MICT, n=10), or served as non-training controls (n=6). SIT consisted of 10-minute sessions with 3 x 20-second all-out cycling sprints (~500W) interspersed with 2 minutes of low-intensity cycling (50W), plus warm-up and cool-down. MICT consisted of 50-minute sessions including 45 minutes of continuous cycling at ~70% maximal heart rate (~110W). Authors measured peak oxygen uptake (VO2peak), insulin sensitivity via intravenous glucose tolerance testing (CS_I), and skeletal muscle mitochondrial content via citrate synthase (CS) maximal activity.
What was found
VO2peak increased by 19% in both training groups (SIT: 32±7 to 38±8 ml/kg/min, p<0.001; MICT: 34±6 to 40±8 ml/kg/min, p<0.001), while controls showed no change (p=0.99). Insulin sensitivity index improved similarly after SIT (4.9±2.5 to 7.5±4.7 x 10⁻⁴ min⁻¹ [µU/mL]⁻¹, p=0.002) and MICT (5.0±3.3 to 6.7±5.0 x 10⁻⁴ min⁻¹ [µU/mL]⁻¹, p=0.013), with no change in controls (p=0.63). Skeletal muscle citrate synthase activity increased similarly after both SIT and MICT (p<0.001) but remained unchanged in controls (p=0.97).
Why it matters
Sprint interval training requiring only 1 minute of intense exercise within a 10-minute session provided cardiometabolic and skeletal muscle adaptations comparable to 50 minutes of continuous moderate exercise.
Limits
The sample size was very small (n=25 total, 6–10 per group) and limited to young sedentary men, precluding generalization to females, older adults, or clinical populations. The abstract does not specify whether group assignment was randomized, and long-term clinical outcomes or real-world adherence were not evaluated.