If you lift weights until your muscles are completely exhausted, it doesn't really matter if you use light weights with many reps or heavy weights with few reps—your calf muscles will grow about the same amount over two months.

Our current analysis shows that lifting light weights to failure builds muscle about the same as lifting heavy weights. The evidence we have reviewed leans toward this finding for calf muscle growth over a two month period. What we have found so far comes from one assertion that we examined. We counted 41 studies support, 0 studies refute this idea. When we say lifting to failure, we mean pushing your muscles until they are completely exhausted and cannot do another repetition. The data we looked at suggests that whether you choose lighter weights with many repetitions or heavier weights with fewer repetitions, your calf muscles will grow about the same amount over two months [1]. The evidence we have reviewed leans toward the idea that the weight you pick matters less than how close you get to that point of complete exhaustion. We want to be clear that this is a partial view. Our current analysis only covers one specific muscle group and a short timeframe. The evidence we have reviewed suggests this pattern, but we will keep tracking new data as it becomes available. Not enough evidence exists yet to say how this applies to every muscle or longer training blocks. For your next workout, focus on pushing each set until you cannot complete another rep with good form. You can safely choose lighter dumbbells or machines and still see steady gains. Just make sure you track your progress and adjust the weight when the exercise starts to feel easy.