Heavy resistance training at retirement age induces 4-year lasting beneficial effects in muscle strength: a long-term follow-up of an RCT.

Objectives: Muscle function and size decline with age, but long-term effects of resistance training in older adults are largely unknown. Here, we explored the long-lasting (3 years) effects of 1 year of supervised resistance training with heavy loads.

Methods: The LIve active Successful Ageing (LISA) study was a parallel group randomised controlled trial at a university hospital in Denmark. Older adults (n=451) at retirement age were randomised to 1 year of heavy resistance training (HRT), moderate-intensity training (MIT) or a non-exercising control group (CON). Primary outcome measure was leg extensor power. Secondary outcomes included maximal isometric quadriceps torque (isometric leg strength) and body composition (dual-energy X-ray absorptiometry (DXA)). Participants completed test procedures at baseline, following the 1-year intervention, and 2 and 4 years post study start.

Results: At the 4-year assessment, 369 participants attended (mean age=71 years, 61% women). The main finding was that across all four time points, there was a significant group×time interaction in isometric leg strength (F_6,1049=8.607, p<0.001, ${\eta }^2$ =0.05). Individuals in HRT maintained baseline performance in isometric leg strength (Baseline: 149.7±51.5 Nm, 4 years: 151.5±51.1 Nm, t(1050)=1.005, p=1.00) while participants in CON and MIT decreased.

Conclusion: In well-functioning older adults at retirement age, 1 year of HRT may induce long-lasting beneficial effects by preserving muscle function.

Trial registration number: NCT02123641.