HIIT ranked top for VO2max, resistance training last

Maximal oxygen uptake, or VO2max, is the standard laboratory index of cardiorespiratory fitness, and it is one of the outcomes that exercise programmes for people living with overweight or obesity are explicitly designed to shift. The problem is choice: aerobic work, intervals, resistance training and combinations of them have all been trialled, usually against a control rather than against each other. That leaves coaches and individuals without a clear sense of which format delivers most per unit of effort. This review set out to compare the available options directly within one statistical framework.

The authors systematically searched five databases from inception to February 2025 for randomised controlled trials testing exercise interventions on VO2max in adults with overweight or obesity. Risk of bias was assessed with the Cochrane tool. A total of 93 randomised controlled trials involving 4,446 participants were included. A Bayesian network meta-analysis with a random-effects model was used to combine direct and indirect evidence, allowing six intervention types to be ranked against one another using the Surface Under the Cumulative Ranking Curve, alongside standardised mean differences with 95% credible intervals.

High-intensity interval training ranked highest, with a SUCRA of 82.5% and a standardised mean difference of 4.85 (95% credible interval 3.90 to 5.80). High-intensity aerobic training followed closely at a SUCRA of 76.7% and an SMD of 4.72, then combined aerobic and resistance training at 69.1% and an SMD of 4.52. Resistance training was the least effective option, with a SUCRA of 18.3% and an SMD of 2.57 (credible interval 1.32 to 3.86). Importantly, all six interventions effectively improved VO2max, so the ranking is about degree of benefit rather than presence or absence of it.

This is consistent with the broader finding that intensity is the main driver of cardiorespiratory adaptation, and it extends that principle specifically to adults living with overweight or obesity. The gap between the top three options is narrow, and their credible intervals overlap heavily, so treating the ordering as definitive would overread the data. Network meta-analysis also relies partly on indirect comparison, which is weaker than a trial that pits two programmes against each other. Questions about adherence, injury risk and how sustainable each format is over years are not answered here.

This is a reason to think that if raising cardiorespiratory fitness is the goal, higher-intensity formats tend to deliver more change than resistance work alone. It is not a reason to abandon resistance training, which still improved VO2max in the pooled analysis and does other things this outcome cannot capture. The differences between intervals, high-intensity aerobic work and combined training are small enough that preference and sustainability plausibly matter as much as the ranking. The headline takeaway is that all six formats moved the needle.