Aerobic high-intensity intervals improve VO2max more than moderate training.
Level 2 - randomized trial
Individual randomized controlled trial
PubMed 17414804 · doi:10.1249/mss.0b013e3180304570
What was done
Forty healthy, nonsmoking, moderately trained men were randomized to one of four 8-week running protocols (3 days/week), all matched for total work and oxygen consumption: 1) long slow distance at 70% HRmax, 2) continuous running at lactate threshold (85% HRmax), 3) 15/15 intervals (15 s at 90-95% HRmax / 15 s at 70% HRmax), or 4) 4 x 4 min intervals (4 min at 90-95% HRmax / 3 min at 70% HRmax). Changes in VO2max, stroke volume, blood volume, lactate threshold, and running economy were evaluated.
What was found
High-intensity interval training produced significantly greater increases in VO2max than long slow distance and lactate-threshold training (P < 0.01). VO2max increased by 5.5% in the 15/15 group (from 60.5 to 64.4 mL/kg/min) and by 7.2% in the 4 x 4 min group (from 55.5 to 60.4 mL/kg/min). Stroke volume increased significantly by approximately 10% following interval training (P < 0.05). The abstract does not provide specific numerical outcomes for blood volume, lactate threshold, or running economy.
Why it matters
This study shows that when total energy expenditure is equated, exercise intensity is the primary determinant of aerobic capacity gains, driven largely by improvements in cardiac stroke volume.
Limits
The sample was small (n = 40 across four arms, ~10 per group) and limited strictly to healthy, moderately trained men, restricting generalizability to women, older adults, sedentary individuals, or clinical cohorts. Specific quantitative results for several secondary endpoints were not reported in the abstract.
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