Heavy or Light Weights? Both Build Muscle, But Heavy Wins for Strength

Original Title

Changes in muscular strength following nine weeks of high- or low-load resistance training.

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Summary

Two groups lifted weights to exhaustion for nine weeks—one used heavy weights, one used light ones. Both got stronger in some ways, but only the heavy group got much stronger at lifting maximum weight.

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Surprising Findings

Low-load training led to nonsignificant decreases in isokinetic torque at fast speeds (60°/s and 120°/s), while high-load maintained or improved strength.

Most fitness advice says 'training to failure' makes load irrelevant—this suggests light weights might actually impair explosive strength, even if muscle size doesn’t change.

Practical Takeaways

If your goal is to increase your max lift (1-RM), prioritize heavier loads (75–85% 1-RM) even if you train to failure.

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