The Science of Lengthened-Position Training: How to Increase Muscle Growth by Up to 2x

Emphasizing muscle stretch can boost hypertrophy up to 2x. See the science and how I apply it daily.

Performing the exact same exercises with one key adjustment can increase muscle growth anywhere from 10% to nearly double. This isn't a marketing claim — it's a principle backed by a robust and growing body of research, and one I apply directly in my own training and clinical practice. The key is emphasizing the lengthened (stretched) position of the muscle during resistance training.

In this post, I'll explain exactly what it means to train a muscle at its lengthened position, walk through the scientific evidence, and show you how to start applying it to your routine today. There are three distinct approaches:

• Training with the muscle at a greater absolute length
• Applying greater resistance specifically in the lengthened portion of the range of motion
• Using a lengthened partial range of motion (ROM)

I'll cover all three in detail below.

Method 1: Training with Greater Absolute Muscle Length

Take the incline bicep curl. Because the arm is positioned behind the torso on an incline bench, the long head of the biceps brachii is placed in a more elongated state before the curl even begins. Compare this to a standard standing curl: the total arc of elbow flexion is identical, but the average length of the biceps throughout the movement is significantly greater during the incline version.

The same principle applies to the triceps. In an overhead tricep extension, raising the arms overhead places the long head of the triceps — which crosses the shoulder joint — in a lengthened position that cannot be replicated by a pushdown. A landmark 2023 study by Maeo et al. confirmed this: the overhead extension group experienced approximately 1.5 times greater hypertrophy in the triceps long head compared to the pushdown group. Remarkably, the other two tricep heads, which don't cross the shoulder joint, also showed 1.4 times greater growth in the extension group — a finding I'll explain further in Method 2.

In my clinical experience, I've observed this pattern consistently across multiple muscle groups, all of which are well supported in the research literature:

• Hamstrings: Seated leg curls — which flex the hip and maximally stretch the hip-crossing portion of the hamstrings — produce greater hamstring hypertrophy than prone (lying) leg curls. A 2021 study found approximately 1.5 times greater whole hamstring volume growth in the seated condition.
• Quadriceps: When performing a leg extension with the torso reclined, the rectus femoris (which crosses the hip joint) is placed in a more lengthened position. Research comparing 40° vs. 90° of hip flexion during the leg extension found up to three times greater rectus femoris growth in the more reclined position. Crucially, the vastus lateralis — which does not cross the hip and therefore does not change length with trunk position — showed no meaningful difference between conditions. This is not a coincidence. Only the muscle that was actually lengthened received the hypertrophic advantage.
• Glutes: Squatting to full depth places the glutes in a more stretched position than partial-depth squats, and the research consistently confirms greater gluteal hypertrophy at greater squat depth.
• Gastrocnemius: Because the gastrocnemius crosses the knee joint, performing standing calf raises (knee extended) places it at a greater length than seated raises (knee flexed). This translates to superior gastrocnemius growth in the standing variation.

Method 2: Applying Greater Resistance at the Lengthened Position

Consider the lateral raise. With dumbbells, the deltoid receives virtually no resistance at its most lengthened position (arm hanging at the side). The peak resistance comes when the arm is roughly parallel to the floor — the point at which the deltoid is the most shortened. A cable lateral raise with the cable set at hip height reverses this: meaningful resistance is applied at the very start of the movement, when the deltoid is most stretched. The absolute length of the deltoid is identical between these two exercises — the difference lies entirely in when the load is heaviest.

Returning to the Maeo 2023 triceps study: the overhead extension group showed 1.4 times greater growth even in the medial and lateral heads of the triceps — muscles that don't cross the shoulder joint and therefore don't change in absolute length when the arms are raised. The most likely explanation is the resistance profile. In a pushdown, the triceps experience minimal load at maximum stretch (the cable runs nearly parallel to the forearm at the bottom of the movement). In an overhead extension, the moment arm is at its greatest precisely when the triceps are most stretched — meaning maximum resistance coincides with maximum muscle length.

The preacher curl is another textbook example of this concept. Unlike the incline curl, the preacher curl does not increase the absolute length of the biceps long head (the arm is in front of the torso, not behind). However, it applies substantial load to the biceps at the elbow-extended (lengthened) position — exactly where a standard standing curl applies almost nothing. This is why I categorize preacher curls and incline curls as distinct tools targeting the same quality (muscle stretch) through different mechanisms.

Method 3: Lengthened Partial Range of Motion

Shortened Partial ROM vs. Full ROM

This comparison is the most intuitive. A 2014 study found that leg extensions performed only in the shortened range produced substantially less quadriceps hypertrophy than full-ROM leg extensions. Similarly, partial-depth squats produce less gluteal growth than squats taken to full depth. Training in a shortened partial ROM is consistently the least effective option.

Shortened Partial ROM vs. Lengthened Partial ROM

This comparison is more revealing. A 2021 study by Sato et al. using the preacher curl directly compared these two conditions — training in the initial (lengthened) portion of the curl versus the final (shortened) portion. The lengthened partial ROM group demonstrated dramatically greater biceps hypertrophy. A parallel finding emerged in the 2014 leg extension research: leg extensions performed in the lengthened range (90°–40° of knee extension) produced significantly more quadriceps growth than those performed in the shortened range (0°–50°). When partial ROMs compete against each other, the lengthened version wins decisively.

Lengthened Partial ROM vs. Full ROM

This is the question that has generated the most scientific interest — and the most practical implications. Prior to 2024, five published studies had compared these two conditions. Four of the five found the lengthened partial ROM group equal to or superior to the full ROM group, despite covering a substantially smaller arc of motion. The fifth study found no meaningful difference between the two conditions.

An important caveat: all five of those studies were conducted in relatively untrained individuals. This matters because researchers have proposed a mechanism called longitudinal hypertrophy — a distinct form of muscle growth in which sarcomeres are added in series along the fiber (lengthening the muscle) rather than in parallel (thickening it). Animal research suggests this type of growth is preferentially triggered by lengthened-position training. Some researchers have argued that longitudinal hypertrophy may be active primarily in beginners and attenuates with training experience.

A recent study led by Brad Schoenfeld, along with Max Coleman, Paul Swinton, Milo Wolf, and a team of researchers including Jeff Nippard, addressed this gap directly. Their participants had an average training age of approximately 4.9 years — genuinely experienced lifters, not beginners. They used a within-subject design, assigning each participant's two limbs to different conditions (one limb trained with full ROM, the other with lengthened partial ROM), which minimized confounding variables such as genetics, diet, and sleep. The result was no statistically significant difference in hypertrophy between the two conditions.

My interpretation is that this null finding is not conclusive evidence against lengthened partials. The study ran for only 8 weeks — a short window in which experienced trainees already grow slowly. Additionally, the actual ROM difference between the two conditions was fairly small (approximately 14° in the bicep curl), which limits how much divergence in outcome we should realistically expect.

The Unified Conclusion

Whether or not lengthened partial ROM ultimately proves superior to full ROM in experienced trainees, one conclusion emerges consistently from the entire body of evidence: the stretched portion of a muscle's range of motion is disproportionately important for hypertrophy. The shortened range, by contrast, consistently produces inferior results in every head-to-head comparison.

This doesn't mean exercises that emphasize the shortened position are bad or should be avoided. In my practice, I encourage trainees to use a variety of movements. But if you're allocating training volume, prioritize stretch-emphasizing exercises — you'll get more hypertrophy per set, which means more results per unit of effort.

Practical Recommendations

Based on the research and my clinical experience training athletes and general population clients, here is how I recommend applying these principles.

Exercise Selection

Include at least one stretch-emphasizing exercise per muscle group in your weekly programming:

• Biceps: Incline curl or preacher curl (both target the lengthened position through different mechanisms — I include both in rotation)
• Triceps: Overhead tricep extension
• Lateral deltoid: Cable lateral raise with the cable set at hip height (not shoulder height)
• Back: T-bar row — as the bar is fixed at one end, the moment arm increases as the weight descends, meaning maximum resistance occurs when the back musculature is most lengthened at the bottom of the pull
• Chest: Dumbbell fly — maximum stretch and maximum resistance coincide at the bottom of the movement

Range of Motion

Never omit the lengthened portion of any exercise. Whether you train through the full ROM or use a lengthened partial, the stretched position must be included. On exercises that don't inherently load the stretched position — such as leg extensions, pec deck flyes, lat pulldowns, and most rowing movements (which all tend to be hardest in the shortened position) — I often extend the final set past failure by continuing with lengthened partial reps. Once you can no longer complete a full rep, restrict subsequent reps to the bottom (stretched) portion and continue until you reach a new failure point.

This technique adds meaningful fatigue, so I limit it to the final set of a given exercise — not every set. The exercises where I currently apply this approach include lat pulldowns, leg extensions, pec deck flyes, chest-supported rows, cable rows, and most rowing variations.

One practical note: if you are already performing an exercise that emphasizes the stretch — such as incline curls, preacher curls, or overhead extensions — there is no need to add lengthened partial reps on top. The stretch stimulus is already built into the movement design.