Mixed
In elderly populations, resistance training using light-to-moderate loads (approx. 45% 1RM) produces strength gains comparable to heavy loads (approx. 80% 1RM), provided the total mechanical work (sets x reps x load) is matched between protocols.
If you are older and want to build strength, you do not need to lift extremely heavy weights. You can use lighter weights (around 45% of your max) as long as you perform enough repetitions to match the total work of a heavy workout. This approach is effective for strength gains and may be safer for those with joint or heart issues.
To conclude, provided a sufficient number of repetitions is performed, RT at lower than traditionally recommended intensities of load may suffice to induce substantial gains in muscle strength in elderly cohorts.
Why this rating
Based on a meta-analysis of 15 studies (448 subjects) with rigorous work-matching controls.
Source
Effects of resistance training with moderate vs heavy loads on muscle mass and strength in the elderly: A meta‐analysis
Robert Csapo et al. · Scandinavian Journal of Medicine and Science in Sports · 2015
This is one finding among thousands. Every one is graded and traced to its source, so you can see what the evidence actually supports. Browse the research →