The Effect of Training Intensity on VO₂max in Young Healthy Adults: A Meta-Regression and Meta-Analysis

Exercise training at a variety of intensities increases maximal oxygen uptake (VO₂max), the strongest predictor of cardiovascular and all-cause mortality. The purpose of the present study was to perform a systematic review, meta-regression and meta-analysis of available literature to determine if a dose-response relationship exists between exercise intensity and training-induced increases in VO₂max in young healthy adults. Twenty-eight studies involving human participants (Mean age: 23±1 yr; Mean VO₂max: 3.4±0.8 l·min^-1) were included in the meta-regression with exercise training intensity, session dose, baseline VO₂max, and total training volume used as covariates. These studies were also divided into 3 tertiles based on intensity (tertile 1: ~60-70%; 2: ~80-92.5%; 3: ~100-250%VO₂max), for comparison using separate meta-analyses. The fixed and random effects meta-regression models examining training intensity, session dose, baseline VO₂max and total training volume was non-significant (Q4=1.36; p=0.85; R²=0.05). There was no significant difference between tertiles in mean change in VO₂max (tertile 1:+0.29±0.15 l/min, ES (effect size) =0.77; 2:+0.26±0.10 l/min, ES=0.68; 3:+0.35±0.17 l/min, ES=0.80), despite significant (p<0.05) reductions in session dose and total training volume as training intensity increased. These data suggest that exercise training intensity has no effect on the magnitude of training-induced increases in maximal oxygen uptake in young healthy human participants, but similar adaptations can be achieved in low training doses at higher exercise intensities than higher training doses of lower intensity (endurance training).