Doing resistance exercises with the elbow muscles stretched out or in varied positions leads to a measurable increase in the size of the elbow flexor muscles in people who regularly work out but are not elite athletes.

We analyzed the available evidence on whether resistance training at long muscle lengths increases elbow flexor size, and what we’ve found so far suggests a consistent pattern: 54 studies or assertions support this idea, and none refute it. The evidence indicates that when people who regularly train but aren’t elite athletes perform resistance exercises that stretch the elbow flexors — like dumbbell curls with a full range of motion — their elbow flexor muscles tend to grow more compared to exercises that don’t emphasize that stretched position. This likely happens because stretching the muscle under load may create more mechanical tension or muscle fiber damage, both of which are signals the body uses to adapt and build tissue. We don’t know exactly how much bigger the muscles get or whether this works the same for everyone, but the pattern across these 54 reports is clear. The term “long muscle length” means the muscle is stretched out — like when your arm is fully extended during a curl — and training in that position appears to be linked to greater muscle growth in the biceps and brachialis. We haven’t seen any data suggesting this approach is ineffective, but we also haven’t seen enough detail to say whether it’s better than other methods for everyone. What we’ve found so far points toward including full-range movements in your routine, especially those that stretch the target muscle under load, as a simple way to potentially support muscle growth in the elbow flexors.