Training with weights almost to failure for five weeks increases the electrical activity in certain muscle fibers during moderate effort, while training with more rest between sets does not produce this change.

We analyzed the available evidence and found that training with weights almost to failure—using 0–1 reps in reserve—may increase electrical activity in muscle fibers of the vastus lateralis during moderate effort, compared to training with more rest and 4–6 reps in reserve [1]. This observation comes from a single study assertion that tracked changes over five weeks, showing higher muscle fiber activation when training closer to failure. No studies in our review contradicted this finding. What we’ve found so far suggests that pushing closer to physical limits during resistance training might lead to greater motor unit recruitment in the vastus lateralis, even when performing movements at moderate intensities. Motor unit firing rate refers to how often nerve signals activate muscle fibers—higher rates can mean more muscle fibers are being engaged. The study did not measure this directly in all conditions, but it did measure electrical activity, which is a common way to estimate motor unit behavior. We don’t know if this effect lasts beyond five weeks, or if it applies to other muscles or different training volumes. The evidence is limited to one assertion, and we haven’t seen data on long-term outcomes, individual differences, or how this might interact with recovery or fatigue. For someone looking to maximize muscle activation during workouts, training closer to failure—leaving 0–1 reps in reserve—might help increase the effort your muscles put in during each set, even if the weight isn’t maximal. But this doesn’t mean you should push to failure every set, as recovery and consistency matter too.