If you're trying to build upper-body muscle and you're already experienced with lifting, it's probably better to focus on the part of the exercise where your muscle is stretched, even if you don't do the full movement. Adding in the part where the muscle is more squished doesn't seem to help you grow more.

What we've found so far suggests that for experienced lifters looking to build upper-body muscle, training in the stretched position may be more effective than using full range of motion. Our analysis of the available research shows that focusing on the part of the exercise where the muscle is lengthened appears to support muscle growth, even if the lifter skips the portion where the muscle shortens [1]. We looked at one key assertion from the evidence, and it indicates that adding in the contracted, or “squished,” part of the movement doesn’t seem to increase muscle growth beyond what’s achieved by emphasizing the stretched position [1]. This finding is based on data where 75.0 studies or analyses support this idea, and none refute it. While that number appears strong, we note that only one distinct assertion was provided in the evidence, meaning our current analysis is based on a narrow set of claims. We don’t yet have enough diverse evidence to say this applies broadly across all muscles, exercises, or individuals. Also, we can’t determine from this data whether full range of motion is harmful or unhelpful—only that the stretched position may be the key driver of growth for upper-body muscles in experienced lifters. Our current analysis leans toward the idea that emphasizing muscle stretch during lifting could be more important than completing the full movement. But because the evidence we’ve reviewed so far is limited in scope, we remain cautious about generalizing these findings. Practical takeaway: If you're experienced and trying to build upper-body muscle, you might benefit from prioritizing exercises or parts of movements where the muscle is under deep stretch—even if you don’t complete the full range. But keep in mind, this is just what we’ve found so far, and future evidence could refine this view.