Some studies say full-range lifting makes muscle fibers longer, but the tools used to measure this might be inaccurate, so we can’t be sure it’s really happening.

If young guys lift weights for eight weeks—whether they go heavy or do more reps—they’ll likely build muscle in their upper body and back, and that can be seen with ultrasound scans.

When people train with their muscles stretched out, the longer their muscle fibers get, the more quickly they tire out during repeated efforts.

If you already lift weights, doing partial reps that fully stretch the muscle builds the exact same amount of muscle as doing full-range reps over two months. As long as you lift the same total weight and do the same number of sets, your muscles will grow at the same rate regardless of which style you pick.

Your muscle fibers don’t get longer with one training method over another—whether you go to failure, use pyramids, or stick to the basics—as long as you do the same total amount of work.