If you lift weights until your muscles can't do another rep, pushing fast on the way up and slowing down on the way back, it helps your muscles grow bigger.

What we've found so far suggests that lifting weights to failure with a fast concentric (lifting) phase and a slow eccentric (lowering) phase may help build muscle. Our analysis of the available research shows this approach is supported by the evidence we've reviewed. We analyzed 71.0 assertions from studies, and all of them support the idea that this type of lifting technique—pushing the weight up quickly, controlling it down slowly, and going until the muscle can’t do another repetition—can contribute to muscle growth [1]. No studies in our review refuted this. The consistent support across the data we examined indicates the evidence leans toward this method being effective for increasing muscle size. However, we want to be clear: our current analysis reflects what we’ve gathered so far, not a final conclusion. We don’t claim this is the only way to build muscle, nor do we say it works for everyone in every situation. The evidence we’ve reviewed focuses on muscle growth outcomes when these specific tempo and effort guidelines are followed. It’s also important to note that “lifting to failure” means stopping when you can’t complete another full repetition with proper form. Doing this with a fast concentric and slow eccentric motion may increase time under tension and muscle activation, both of which are factors linked to muscle growth. Still, not every person or program may benefit equally. Individual differences, training experience, and recovery capacity can all influence results. We don’t have enough data yet to say how this method compares to others in the long term, or for different goals. Practical takeaway: If your goal is to build muscle, lifting to failure with a quick lift and slow lowering might help. Just make sure your form stays safe, and don’t assume it’s the only way that works.