Understanding Full vs Partial Range of Motion in Strength Training
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When you lift weights, you might hear advice like “go all the way down” or “don’t lock out your elbows.” These cues refer to something called range of motion (ROM). It simply means how far a joint moves during an exercise. A full range of motion (fROM) means moving through the entire possible path, like lowering a squat until your thighs are parallel to the ground and then standing up fully. A partial range of motion means working through only part of that path.
Recently, there’s been growing interest in lengthened partial range of motion (lpROM) doing only the first half of the movement when the muscle is stretched. Some lifters believe that this style builds more muscle because the stretched position might create higher tension on the muscle fibers. But is that really true?
A new large-scale study published in the Journal of Sports Sciences (2025) set out to answer this question.
What the Researchers Wanted to Find
The study aimed to compare full range of motion (fROM) training with lengthened partial range of motion (lpROM) training. The main question was: Does training with lengthened partials lead to more muscle growth than full-range training?
The research team from the USA and UK ran a 12-week randomized controlled trial across 15 training centers. Nearly 300 trained participants took part. This was one of the largest studies ever done on this topic.
How the Study Was Done
Participants were divided into two groups:
- fROM group: performed exercises through the full range of motion
- lpROM group: performed exercises only through the stretched half of the range
Both groups trained twice a week using similar exercises, loads, and supervision. The key difference was how much of each exercise they performed. The workouts included both upper and lower body movements, such as leg presses, curls, and triceps extensions.
Researchers measured changes in muscle size (cross-sectional area) of the arms and thighs, as well as strength gains on major lifts like the leg press and chest press.
What They Found
After 12 weeks, both groups saw small increases in muscle size and strength. However, there were no meaningful differences between the full and partial range of motion groups.
- Arm muscle growth difference: almost zero
- Thigh muscle growth difference: almost zero
- Strength improvements: similar in both groups
In other words, both methods worked equally well for trained individuals.
The researchers noted that the differences between fROM and lpROM were so small that they were practically equivalent. Even in this large, well-controlled study, the results suggest that both training styles can produce similar outcomes.
What This Means for You
If you’ve been wondering whether partial reps are “better” than full reps for muscle growth, this study suggests they’re about the same—at least when performed properly.
Here’s what you can take away:
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Both full and partial reps build muscle.
As long as you’re training hard, close to failure, and using good form, you’ll make progress.
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Partial reps can be useful in specific cases.
If you want to reduce joint stress, focus on a muscle’s stretched position, or work around an injury, partial reps are a valid option.
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For most lifters, variety may be best.
Mixing both styles sometimes doing full range, sometimes partial—can keep your training balanced and challenging.
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Don’t overthink small differences.
The researchers emphasized that effects in trained people are often quite small. The key is consistency, not chasing minor tweaks.
The Bigger Picture
This study also highlights a broader point: once you’ve been training for a while, progress becomes slower. The body adapts over time, and gains in muscle and strength follow a pattern where improvements are large in the beginning and then taper off. Researchers call this a linear-log growth model, meaning you gain a lot early, and smaller amounts later.
So, if you’ve been lifting for months or years and notice slower progress, it doesn’t mean your program is failing. It’s just how muscle growth works.
Final Thoughts
The bottom line is simple: whether you train with a full range or a lengthened partial range, you can build muscle effectively. What matters most is putting in consistent effort, maintaining proper form, and progressively challenging your muscles over time.
If you enjoy using full range of motion, keep doing it. If you like experimenting with partial reps, that’s fine too. Both are tools in your training toolbox and now you have scientific proof that either can help you grow stronger and more muscular.
