It may look like you’re skipping a key part of a rep by performing lengthened partials, but a new study published in The Journal of Strength and Conditioning Research proves the merits of the method.
Lengthened partials involves maximising time under tension by completing reps in the bottom portion of an exercise, where the muscle is most stretched. And unlike with shortened partials or full range-of-motion reps, this also means you miss the easier lockout phase. According to the latest science, that’s no bad thing.
The Study
Researchers randomly assigned 45 untrained individuals to one of four groups: one trained at 80% of their one-rep max using shortened partials (such as half squats), another trained at 55% of their one-rep max using lengthened partials, a third performed full range-of-motion reps at 80% of their one-rep max, and a control group completed eight weeks of knee extensor exercises.
Participants were training their quads over the course of eight weeks, completing prescribed sets, reps and loads using squats, split squats, leg presses or leg extensions. Researchers then measured each person’s muscle thickness and muscle architecture, such as muscle fascicle length, which is the physical length of a bundle of muscle fibres, in three different locations on the quad, to determine if there was one style of training superior to the others.
The Results
Participants performing lengthened partials achieved similar muscle growth to those using a full range of motion, and produced significantly greater muscle thickness gains than those in the shortened partials group at two of the three quad locations.
That’s despite those doing lengthened partials using a lower intensity and less weight over the course of the eight weeks.
‘This study provides novel evidence that moderate-intensity resistance training with partial range of motion at long muscle lengths elicits similar hypertrophic and superior fascicle length adaptations as high-intensity full range-of-motion training,’ researchers concluded.
What Does This Mean for You?
So, it makes sense to start incorporating more lengthened partials into your training, right? Not definitively.
Though the researchers wanted to know whether more muscle tension leads to more muscle growth, they didn’t measure the tension inside the quad itself. Instead, they estimated the force transmitted through the tendon attached to the muscle – which doesn’t always match muscle tension because of the way muscles are built and how they transfer force.
Fascicle length, meanwhile, increases much more rapidly and commonly in beginner lifters. While the muscle growth increase was largest in the lengthened partials group, much of that could be attributed to muscle lengthening rather than thickening. For more experienced lifters, lengthened partials might not produce the same results.
What is certain that for most people, full range-of-motion reps should remain the foundation of training, with shortened partials reserved for specific programming.
Whether lengthened partials are actually superior to reps completed with a full range of motion isn’t conclusive, though, and will likely depend on specific exercises and the individual’s goal. For example, if you want to focus on building a bigger chest in the bench press, then you might opt against locking out your triceps at the top of the rep to maintain tension on the intended muscle. That’s a lengthened partial performed with purpose, rather than just for the sake of doing so.
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