The Effects of Long Muscle Length Isometric versus Full Range of Motion Isotonic Training on Regional Quadriceps Femoris Hypertrophy in Resistance-Trained Individuals.

For people who are already trained, lifting weights with muscles stretched out does not result in more muscle growth than lifting with muscles shortened, and it does not result in less muscle growth than lifting through a full range of motion.

When training volume and intensity are the same, lifting weights with greater resistance at longer muscle lengths results in the same amount of muscle growth as lifting with greater resistance at shorter muscle lengths.

Doing static leg exercises with your thigh muscles fully stretched might grow the upper part of your thigh more than doing regular leg exercises that move through a full range, but both types of exercise end up making your whole quadriceps muscle about the same size.

If you train your quads using either holding a static position with your legs stretched out or doing full squat-like movements, both ways build your thigh muscles about the same amount — neither one is better than the other.

If you're already someone who lifts weights, doing either static holds with your muscles stretched out or full-range weight exercises won't make the outer part of your thigh noticeably bigger in just six weeks.

In people who regularly lift weights, training with static muscle contractions at stretched muscle positions and training with full-range dynamic movements produce similar increases in quadriceps muscle size over six weeks, though static training leads to slightly more growth in the upper part of the front thigh.