Resistance training and inter-interindividual response differences on cardiorespiratory fitness in older adults: An ancillary meta-analysis of randomized controlled trials

Examine true inter-individual response differences (IIRD) as a result of resistance training on cardiorespiratory fitness in older adults. Data from a recent meta-analysis of 22 randomized controlled trials representing 552 men and women (292 resistance training, 260 control) ≥ 60 years of age were included. The primary outcome was cardiorespiratory fitness (VO_2max) in ml^.kg^−1.min⁻¹. Using the inverse variance heterogeneity (IVhet) model, statistically significant treatment effect (resistance training minus control) increases in VO_2max in ml^.kg^−1.min⁻¹ were found (mean, 1.8, 95% CI, 0.4 to 3.3 ml^.kg^−1.min⁻¹, p = 0.01; Q = 82.8, p < 0.001; I²= 74.6%, 95% CI, 61.6 to 83.3%; (Formula presented.) =1.1). The 95% prediction interval (PI) was −0.8 to 4.5 ml^.kg^−1.min⁻¹. However, no statistically significant IIRD was observed (mean, 0.6, 95% CI, −1.1 to 1.4 ml^.kg^−1.min⁻¹; (Formula presented.) =1.5). The 95% PI was −1.8 to 2.0 ml^.kg^−1.min⁻¹. In conclusion, while progressive resistance training may increase VO_2max in ml^.kg^−1.min⁻¹, a lack of true resistance-training-associated IIRD exist.