There are no nonresponders to resistance-type exercise training in older men and women

Objective To assess the proposed prevalence of unresponsiveness of older men and women to augment lean body mass, muscle fiber size, muscle strength, and/or physical function following prolonged resistance-type exercise training. Design/Setting/Participants A retrospective analysis of the adaptive response to 12 (n = 110) and 24 (n = 85) weeks of supervised resistance-type exercise training in older (>65 years) men and women. Measurements Lean body mass (DXA), type I and type II muscle fiber size (biopsy), leg strength (1-RM on leg press and leg extension), and physical function (chair-rise time) were assessed at baseline, and after 12 and 24 weeks of resistance-type exercise training. Results Lean body mass increased by 0.9 ± 0.1 kg (range: -3.3 to +5.4 kg; P <.001) from 0 to 12 weeks of training. From 0 to 24 weeks, lean body mass increased by 1.1 ± 0.2 kg (range: -1.8 to +9.2 kg; P <.001). Type I and II muscle fiber size increased by 324 ± 137 µm2 (range: -4458 to +3386 µm2; P = .021), and 701 ± 137 µm2 (range: -4041 to +3904 µm2; P <.001) from 0 to 12 weeks. From 0 to 24 weeks, type I and II muscle fiber size increased by 360 ± 157 µm2 (range: -3531 to +3426 µm2; P = .026) and 779 ± 161 µm2 (range: -2728 to +3815 µm2; P <.001). The 1-RM strength on the leg press and leg extension increased by 33 ± 2 kg (range: -36 to +87 kg; P <.001) and 20 ± 1 kg (range: -22 to +56 kg; P <.001) from 0 to 12 weeks. From 0 to 24 weeks, leg press and leg extension 1-RM increased by 50 ± 3 kg (range: -28 to +145 kg; P <.001) and 29 ± 2 kg (range: -19 to +60 kg; P <.001). Chair-rise time decreased by 1.3 ± 0.4 seconds (range: +21.6 to -12.5 seconds; P = .003) from 0 to 12 weeks. From 0 to 24 weeks, chair-rise time decreased by 2.3 ± 0.4 seconds (range: +10.5 to -23.0 seconds; P <.001). Nonresponsiveness was not apparent in any subject, as a positive adaptive response on at least one training outcome was apparent in every subject. Conclusions A large heterogeneity was apparent in the adaptive response to prolonged resistance-type exercise training when changes in lean body mass, muscle fiber size, strength, and physical function were assessed in older men and women. The level of responsiveness was strongly affected by the duration of the exercise intervention, with more positive responses following more prolonged exercise training. We conclude that there are no nonresponders to the benefits of resistance-type exercise training on lean body mass, fiber size, strength, or function in the older population. Consequently, resistance-type exercise should be promoted without restriction to support healthy aging in the older population