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) in mlkgmin. Using the inverse variance heterogeneity (IVhet) model, statistically significant treatment effect (resistance training minus control) increases in VO in mlkgmin were found (mean, 1.8, 95% CI, 0.4 to 3.3 mlkgmin,  = 0.01; Q = 82.8,  < 0.001; = 74.6%, 95% CI, 61.6 to 83.3%; =1.1). The 95% prediction interval (PI) was -0.8 to 4.5 mlkgmin. However, no statistically significant IIRD was observed (mean, 0.6, 95% CI, -1.1 to 1.4 mlkgmin; =1.5). The 95% PI was -1.8 to 2.0 mlkgmin. In conclusion, while progressive resistance training may increase VO in mlkgmin, a lack of true resistance-training-associated IIRD exist.