In untrained young men undergoing volume-load-equated unilateral calf-raise training, performing additional partial-range-of-motion repetitions after reaching failure with full range of motion results in equivalent muscle hypertrophy of the gastrocnemius medialis and lateralis compared to traditional full-range-of-motion training, with both approaches increasing muscle thickness by approximately 8% over a 10-week period.

When the calf muscle is stretched while contracting, the titin protein inside muscle fibers gets pulled tight and binds to other parts of the muscle structure. This pulling activates signals that tell the muscle to add more repeating units called sarcomeres end-to-end, making the muscle fibers longer and thicker over time. This happens whether the person does full or partial reps after failure, as long as the muscle is under tension at a stretched position.