In adults who regularly lift weights, performing resistance exercises with either low or high effort close to failure for five weeks leads to about a 10% increase in maximum knee extension strength,...

We analyzed the available evidence and found that in adults who regularly lift weights, both low and high effort during resistance training lead to similar gains in knee strength over five weeks. Specifically, one assertion shows that maximum knee extension strength increased by about 10% regardless of how close to failure the exercises were performed [1]. The evidence we’ve reviewed so far does not suggest that one level of effort — whether low or high RIR — produces stronger results than the other. RIR stands for “reps in reserve,” which means how many more reps you could have done before reaching failure. Low RIR means you stopped close to failure, while high RIR means you stopped well before. In this case, both approaches resulted in the same amount of strength gain in the knee extensors. We have not seen any studies in our review that contradict this finding. However, the total number of assertions analyzed is limited to just one, and while it supports the idea that effort level doesn’t matter for this outcome, we recognize that more research could add nuance. The evidence we’ve reviewed so far leans toward the idea that trained individuals can achieve similar knee strength improvements whether they train with low or high RIR. For someone looking to build knee strength, this means you don’t need to push to absolute failure every session to see results. You can choose a level of effort that feels sustainable and still expect comparable gains over time.