Mixed
High-load resistance training (>60% 1RM) produces significantly greater gains in maximal strength (1RM) compared to low-load resistance training (≤60% 1RM), even when both are taken to failure.
If your primary goal is to increase your maximum lifting capacity (1RM), you should prioritize heavier weights (above 60% of your max). While light weights will still make you stronger, heavy weights will make you stronger faster and to a greater degree. However, light weights are still a valid tool for building strength, especially for joint health or volume accumulation.
Gains in 1RM strength were significantly greater in favor of high- vs. low-load training... The findings indicate that maximal strength benefits are obtained from the use of heavy loads.
Why this rating
Meta-analysis of 14 studies for 1RM strength showing significant difference (p=0.003).
Source
Strength and Hypertrophy Adaptations Between Low- vs. High-Load Resistance Training: A Systematic Review and Meta-analysis
Brad J. Schöenfeld et al. · The Journal of Strength and Conditioning Research · 2017
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