Lengthened Partials Boost Muscle Growth
New research highlights "lengthened partials" as an emerging hypertrophy technique that may enhance muscle growth compared to full-range reps, particularly for experienced lifters. The method involves performing partial reps at the point where muscles are most stretched — like the bottom of squats or bench press — with evidence cited by Dr. Milo Wolf showing superior results. An 8-week review of the Tactical Barbell Operator program adapted for strongman training showed significant strength gains across compound movements, emphasizing heavy lifts with flexible accessory work.
The concept of "lengthened partials" isn't new, with roots in old-school bodybuilding techniques. Bodybuilding legends like Arnold Schwarzenegger and Larry Scott utilized partial reps, often at the end of a set, to increase time under tension and metabolic stress, referring to them as "burns." This historical application focused on overloading muscles beyond the limits of full-range-of-motion repetitions. Recent scientific inquiry has brought more precision to this method, focusing specifically on the stretched portion of an exercise. A key idea being explored is stretch-mediated hypertrophy, which suggests that placing tension on a muscle while it is in a lengthened state is a significant driver of muscle growth. This has led to studies comparing lengthened partials directly with full range of motion exercises. A 2025 study co-authored by Dr. Milo Wolf investigated the effects of an 8-week upper-body training program on trained individuals. The research, published in the journal *PeerJ*, found that lengthened partial repetitions produced similar improvements in muscle thickness and strength-endurance when compared to full range of motion reps. This particular study involved 30 resistance-trained participants and had each individual train one arm with lengthened partials and the other with a full range of motion, allowing for a direct comparison within each person. The results indicated that while emphasizing the stretched position is important for muscle growth, adding the shortened portion of the lift (as in full ROM) did not provide additional hypertrophic benefits in this context. While some studies have suggested that lengthened partials could be superior to full range of motion, with one study on calf training showing double the growth, the overall body of evidence is mixed. As of late 2025, a meta-analysis of around 40 studies indicated that a lengthened training style consistently matches or exceeds the muscle growth seen from training at shorter muscle lengths. The practical application of lengthened partials involves performing reps in the bottom half of a movement where the target muscle is most stretched. For example, this would be the lower portion of a bicep curl or the deep stretch of a dumbbell fly. Proponents suggest this method can be used to extend a set past failure or as the primary style for all reps within a set.
