In untrained young women, performing bicep exercises using only the first half of the movement range for eight weeks leads to more muscle growth in the lower part of the biceps and greater strength gains than using only the second half of the range.

We analyzed the available evidence and found that in untrained young women, training the elbow flexors through the initial range of motion—meaning the first half of the movement—was associated with more muscle growth in the lower part of the biceps and greater strength gains compared to training through the final range alone [1]. This conclusion is based on one assertion that supports this pattern, with no studies or claims contradicting it. The evidence we’ve reviewed so far leans toward the idea that starting the movement from a fully stretched position and stopping before full contraction may be more effective for building muscle and strength in this group. This could be because the initial range places more tension on the muscle fibers when they are lengthened, which may stimulate growth differently than the shortened position. However, we only have one assertion to work with, and it does not include details like sample size, training volume, or how muscle growth was measured. We don’t know if these results would hold for trained individuals, men, or older adults. We also can’t say whether training through the full range would be better overall, since that comparison wasn’t tested here. The finding is specific to untrained young women performing bicep exercises over eight weeks using only partial ranges. For someone just starting out, this suggests that focusing on the first half of the curl—like lifting the weight from the bottom to about halfway up—might help build biceps strength and size more than only doing the top half. But more research is needed to confirm this and understand how it applies beyond this group.