Twelve RCTs (reported in 13 publications; 504 participants) were included in the review. Trial quality ranged from 2 to 3 out of 5 points on the Jadad score, and 4 to 8 out of 10 on the PEDro score. Most trials did not describe or have adequate allocation concealment or blinded outcome assessors. None of the trials were excluded from the main analyses on the basis of the quality assessment. There was no difference in the significance of the treatment effects when low quality trials (scoring below 5 on the PEDro scale) were removed from any analysis.
Cardiovascular fitness: Combined aerobic and resistance training had a beneficial effect on peak exercise capacity in three trials (SMD 0.88, 95% CI 0.45 to 1.31; Ι²=0%) and a beneficial effect on peak oxygen uptake in nine trials, although this did not reach conventional levels of statistical significance (WMD 0.41mL/kg/min, 95% CI -0.05 to 0.88; Ι²=30%), compared with aerobic training. There was no evidence of statistical heterogeneity for either outcome. Subgroup analyses for peak oxygen uptake found no effect for sample size, trial duration, intensity of weight prescribed, or inclusion of a period of aerobic prior to the introduction of resistance training.
Ventilatory anaerobic threshold (three trials): Combined training had a beneficial effect on oxygen uptake occurring at the ventilatory anaerobic threshold (WMD 1.42ml/kg/min, 95% CI 1.63 to 4.47) compared with aerobic training. Despite the confidence interval suggesting otherwise, the authors stated that this effect was not significant. The authors also stated that there was significant heterogeneity (Ι² not reported).
Body composition (three trials): Combined training had a beneficial effect on fat-free mass (WMD 0.88kg, 95% CI 0.39 to 1.36), per cent body fat (WMD -2.3%, 95% CI -3.59 to -1.02) and trunk fat (SMD -0.56, 95% CI -0.96 to -0.15) when compared with aerobic training. None of these analyses showed any heterogeneity (Ι²=0%).
Muscular strength: Combined training had a beneficial effect on lower body strength in seven trials (SMD 0.77, 95%CI 0.49 to 1.04; Ι²=0%) compared with aerobic training. Upper body strength was reported in nine trials; significant heterogeneity was found, so the authors reported a post-hoc analysis eight trials (excluding one trial on women only) and found a a beneficial effect of combined training (SMD 1.07, 95% CI 0.76 to 1.38).
Health-related quality of life (three trials): Combined training and aerobic-only training had beneficial effects on various quality of life domains.
Adverse events: Most trials reported no adverse events. The mean proportion of patients who discontinued the trials were 14.2% for aerobic training and 11.5% for combined training .