VO2max Trainability and High Intensity Interval Training in Humans: A Meta-Analysis

This meta-analysis examined 37 studies on interval training and VO2max to quantify the magnitude of improvement possible through high-intensity training. The researchers evaluated how much VO2max can actually change — a concept called "trainability" — and whether specific training variables like interval duration, intensity, and frequency predicted the size of those gains. Their sample covered a wide range of participants, fitness levels, and training protocols.

The mean VO2max increase across all 37 studies was 0.51 liters per minute — a clinically meaningful improvement. Studies using longer interval durations (two to four minutes at high intensity) produced the largest gains, averaging 0.8 to 0.9 L/min. The analysis found that individuals who were less trained at baseline tended to show the greatest relative improvements, suggesting that men over 50 who have been inactive may have the most to gain from starting a sprint program.

This foundational meta-analysis is significant because it quantifies what is actually achievable. VO2max can be meaningfully improved at any age with the right training stimulus. The study also noted that even relatively brief intervals — down to 30 seconds — produced consistent VO2max gains when performed at sufficient intensity, making this approach practical for older men with time constraints or those building up their capacity gradually. The data reinforces that interval structure matters, but that almost any high-intensity protocol outperforms low-intensity steady-state work.