Lengthened Partials Training Technique

The concept behind lengthened partials is known as stretch-mediated hypertrophy, which suggests that loading a muscle in its most stretched position creates high levels of mechanical tension. This tension is a primary driver for signaling muscle growth, potentially leading to the creation of new sarcomeres, the basic contractile units of muscle fiber. While some studies have shown lengthened partials to be superior to full range of motion for muscle growth, with one study on calf raises showing double the growth, the overall evidence is mixed. More recent research, including a 2025 study co-authored by Dr. Milo Wolf, found similar muscle growth and strength endurance between lengthened partials and full range of motion training in trained individuals. This technique is most effective for exercises that are hardest at the top of the movement, where the muscle is fully contracted. Good candidates include preacher curls, lat pulldowns, seated cable rows, leg curls, and overhead triceps extensions. For these movements, the focus is on performing reps only in the bottom, stretched half of the exercise. Conversely, exercises like barbell squats and bench presses may pose a higher risk when performing lengthened partials without safety bars or a spotter, as you may not have the strength to complete a full rep to safely re-rack the weight. For compound movements, using machines like a Smith machine or hack squat can provide a safer alternative. One common application is to use lengthened partials as a set-extension technique. After reaching muscular failure with a full range of motion, you can continue the set by performing several additional repetitions in the stretched position. It's crucial to maintain proper form and avoid using momentum, as loading a muscle in its most stretched and vulnerable position can increase the risk of injury to connective tissues. The technique can also be highly fatiguing, so it may not be suitable for every set of every workout.