When performing resistance exercises that stretch the elbow flexor muscles more, the muscles grow larger in cross-sectional area than when the same exercises are done with less stretch.

We analyzed the available evidence on whether resistance training at longer muscle lengths builds bigger elbow flexors than training at shorter lengths, and what we’ve found so far is unclear. One assertion claims that exercises stretching the elbow flexors more lead to greater muscle growth in cross-sectional area compared to exercises with less stretch, and this assertion is listed as supported by 54.0 studies and refuted by 54.0 studies [1]. This balance means the evidence does not lean one way or the other. The same number of reports support and challenge the idea, which suggests the findings are inconsistent or possibly based on different methods, populations, or measurements. We cannot say whether stretching the elbow flexors more during exercises like curls leads to bigger muscles, because the data we’ve reviewed does not show a clear pattern. It’s possible that factors like training volume, intensity, rest periods, or individual differences affect outcomes in ways not captured here. Without more consistent results across studies, we can’t determine if muscle length during training plays a meaningful role in elbow flexor growth. For now, if you’re training your biceps and triceps, focusing on controlled movements, full ranges of motion, and progressive overload remains a reasonable approach — but we don’t have enough consistent evidence to say that stretching the muscles more during the exercise will make them bigger than training with less stretch.