Lengthened Partials: The 2025 Science on Stretch-Mediated Hypertrophy

The Stretch Position Myth Is Dead

For years, the bro-science dogma was simple: complete the full range of motion (ROM) for every rep, or you're leaving gains on the table. Recent research from 2024 and 2025 has upended this, revealing that focusing on the stretched portion of a lift—the 'lengthened partial'—is not just effective, but in some cases superior to full ROM for hypertrophy.

What Are Lengthened Partials?

A lengthened partial is a repetition where you deliberately limit the range of motion to emphasize the portion of the lift where the target muscle is maximally stretched. For example, performing a leg extension but only working through the bottom 60% of the movement where the quads are elongated. This differs from cheating reps; the tension remains constant, but the shortened position is eliminated.

The Science Behind Stretch-Mediated Hypertrophy

Studies published in the Journal of Applied Physiology and highlighted by researchers like Brad Schoenfeld and Milo Wolf have shown that mechanical tension in the lengthened position triggers unique signaling pathways. One 2024 study found that training in the stretched range produced similar, and sometimes greater, increases in muscle thickness compared to full ROM.

A key 2025 trial on calf training delivered a stark result: participants performing only the stretched portion of calf raises saw 43.3% greater relative growth than those using full ROM or shortened partials. This suggests stretch-mediated hypertrophy is a potent, underutilized tool.

Why This Matters for Time-Efficient Training

If you're tracking your workouts in GymNotes, this is a game-changer for productivity. You can achieve equal or better stimulus with less total volume. Instead of chasing 15 sets of full ROM chest work, you might do 10 sets of chest flyes emphasizing the stretch. This respects the 'diminishing returns' research showing that per-session hypertrophy benefits plateau around 11 fractional sets.

Practical Applications for Lifters

1. Squats and Leg Presses: Focus on deep, controlled negatives. Consider paused reps in the hole to maximize time under tension at the stretched quads and glutes.

2. Chest Training: Incline dumbbell flyes or cable crossovers performed with a focus on the stretch at the bottom position are brutally effective.

3. Back and Lats: Straight-arm pulldowns or chest-supported rows with an exaggerated stretch at the bottom can elicit a powerful pump and growth stimulus.

4. Triceps: Overhead extensions are superior to pushdowns for a reason—they keep the long head under tension in its stretched position.

The Minimalist's Advantage

This approach aligns perfectly with the GymNotes philosophy of minimalism and data. By isolating the most growth-promoting portion of the rep, you can shorten your sessions, reduce junk volume, and focus on quality. Track your sets, note which exercises feel best in the stretched position, and double down on those. It's not about training less hard; it's about training with more anatomical intelligence.

The era of mindlessly grinding out full ROM reps is over. The data is clear: if you want to maximize your time in the gym, it's time to embrace the stretch.