If you want to grow, you need to lift with a full range of motion, right? That’s a truism as old as Muscle Beach’s glory days (or even older), and still popping up in fresh ways, as in DC’s loaded stretches. Rightly or wrongly (and I think most lifters suspect the former), loaded lengthening of the prime muscle in a given lift is regarded as a key factor in hypertrophy. Just look at elitefts’ John Meadows: “stretch” and “pump” form a two-part cadence that echoes throughout his programming.
Yet until recently, science hasn’t quite looked at this axiom with an inquisitive eye.
Gerald McMahon and a team of fellow Brits addressed this shortcoming, and their findings hint at a great deal of truth in the adage.
MUSCULAR ADAPTATIONS AND INSULIN-LIKE GROWTH FACTOR-1 RESPONSES TO RESISTANCE TRAINING ARE STRETCH-MEDIATED
GERARD McMAHON, MSc, CHRISTOPHER I. MORSE, PhD, ADRIAN BURDEN, PhD, KEITH WINWOOD, PhD, and GLADYS LEOPOLDINE ONAMBELE, PhD
Muscle and Nerve 49: 108-119, 2014
The experiment’s premise is simple: if changes in muscle length during a lift affect strength and/or muscle gains, then a simple lifting protocol focusing on range of motion would reveal this relationship.
His team brought in 31 subjects of mixed gender who were unfamiliar with lifting or were detrained for at least a year. They were then randomly assigned to three groups: an experimental group that would lengthen (stretch) the active muscle to a large degree during the exercise protocol; an experimental group that would not let their muscle lengthen as much; and a control group that did nothing.
Given the availability of related data and lifting implements, I’m not surprised to see the researchers chose the quadriceps as their topic of study. Each experimental group covered 50 degrees of motion in the leg extension, squat, Bulgarian squat, Sampson chair (i.e., paused wall squats), and leg press. The “long” group performed all of their exercises through the bottom range of motion where the quads were stretched, while the “short” group worked in the end ranges of these lifts. To give an example, the long group started as most people do on the seated leg extension, with their lower leg perpendicular to the floor. Rather than finishing the lift, they extended to just past the halfway point of the movement. The short group started around the halfway point and then lifted until their legs were fully extended at 0 degrees.
[You might be wondering why the team chose an overlapping 50 degree ROM instead of an evenly split 45 degree ROM; it turns out most of the literature explores strength at 90 and 50 degrees, so it made sense to follow suit for comparison’s sake.]
Anyone familiar with these exercises knows that there’s a marked change in difficulty that accompanies the change in knee angle during execution (e.g., a squat or leg press tends to be easier at the top of the movement, closer to extension). Basically, this means that if each group were to use identical weights, the effort they put into the lifts (and the resulting rep ranges) would be widely different. It’d be such an apples-and-oranges comparison that there’d be no intra-study way to concretely tease out the role of muscle lengthening.
The researchers took this problem on by adjusting the load to account for these changes in difficulty. They crunched some numbers involving the patella tendon’s changing moment arm and voila: the lengthened group would train with loads of roughly 55% of their one rep max in the relevant ROM of each movement, while the short group would use around 80% of their 1 RM in the relevant ROM of each movement.
Though the exact program wasn’t provided, the subjects seemed to follow a linear model using the classic Delorme-inspired prescription of 3-4 sets of 8-10 reps for each lift, performed three times per week, over eight weeks. Because two weekly sessions were held on-site at the lab, and the third was conducted at home, I imagine the leg extension, squat, and leg press were conducted during the lab days, and the Sampson squat performed at home (the Bulgarian could go either way.) 1 RMs were reassessed every two weeks and the experimental loads adjusted to match. To add a little more interest to the proceedings, the researchers sought to clarify the impact of stretch on detraining, so there were follow-up reviews two and four weeks after the exercise period.
Data collection was fairly standard. Goniometers were taped to lifters’ knees to track the range of motion, and while these weren’t always measured by lab techs, significantly screwing up the prescribed ROM during the home sessions strikes me as pretty unlikely. Fairly reliable tests like EMG, DEXA, and ultrasound were used to determine post-experiment results. And where there were significant outcome differences between the short and long groups, the results were eye-catching:
- Muscle length increase: 29% in the long group, 14% in the short group
- Muscle cross-section increase: 53% in the long group, 18% in the short group
- Strength increase: 26% in the long group, 7% in the short group
- Detraining: the long group better kept strength and size gains
You can’t draw ironclad programming strategies from this, though. If you keep an eye on traditional bodybuilding recommendations, the cross-section results lend weight to the classic dictum of feeling the stretch in a given lift. Likewise, we see some scientific underpinnings for the adage of “partial movements lead to partial results.” I feel comfortable saying this just because the actual volume of work (and accordingly, the hypothetical hypertrophic potential) of the short group was so much greater than the long group. I think it’s safe to say that, all other things beings equal, a novice trainee would do well to avoid partials and embrace full-ROM movements. I think it’s also safe to say that a lifter seeking hypertrophy should focus on lifts that lead to a significantly elongated muscle.
The changes in muscle length I’m more hesitant to comment on, since there’s an interplay of resting tension and fascicle length going on that I’m not sure anyone’s really documented with certainty. It may be that this has some promise as a mobility modality, but that’s just me speculating. The differences in strength gain don’t interest me as much, just because here the leverage adjustments are big factor, though what was discovered in the detraining period caught my eye. Basically, the long group kept more of their strength gains over the four weeks, while the short group regressed to an almost untrained state. While I don’t think the magnitude of change would be anywhere near as significant for a trained lifter, it does make me wonder if there’s some information here relevant to tapering powerlifters, particularly Westside-style lifters who rotate partials and box work.
Even if this study were to be supported by more thorough research down the road, I don’t see a reason to dismiss partials ever springing up: partials are often safer, can be better at addressing weak points, and might better trigger other hypertrophy factors. That said, if you haven’t recently considered muscle elongation as a factor in your sessions, there’s some cause to revisit the idea.
Photo courtesy of Jeffrey Sygo at www.symiphotography.com
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