There is not enough scientific research yet to determine whether training muscles at longer or shorter lengths leads to better muscle growth.

We analyzed the available evidence on whether training muscles at longer or shorter lengths leads to better muscle growth, and what we’ve found so far is that there isn’t enough research to say one approach is better than the other. While 59 studies or assertions point to this question being relevant, none of them provide clear, direct evidence to guide training based on muscle length [1]. This doesn’t mean training at different lengths doesn’t matter — it means we haven’t seen enough high-quality, controlled studies that compare muscle growth outcomes when muscles are trained in stretched versus shortened positions. Some of the existing work looks at how tension or muscle activation changes with joint angle, but those findings don’t directly translate to long-term muscle growth. We also haven’t seen consistent patterns across different muscles, populations, or training protocols that would let us draw a reliable conclusion. The lack of refuting studies doesn’t mean the idea is proven — it just means no studies have yet contradicted the claim that we don’t know enough. Without clear comparisons between training at long versus short muscle lengths, and without measurements of actual muscle growth over time, we can’t say whether one is more effective. For now, if you’re training for muscle growth, focusing on progressive overload, sufficient volume, and proper form remains the most supported approach. Whether your muscles are stretched or shortened during a movement may matter, but we don’t yet have the evidence to tell you how to use that information.