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Why range of motion matters

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Chris Beardsley is a biomechanics researcher. He is also the editor of Strength and Conditioning Research. He is based in Loughborough, Leicestershire.

If you walk into any gym, the chances are that the guy hanging from the chin-up bar isn’t doing full reps. Instead he’ll be doing some sort of juddering movement where the angle of his arms changes from bent to ever-so-slightly more bent. You probably mutter something about ‘terrible range of motion’ under your breath before starting your own workout, making sure you go to full extension and flexion on each rep. You do this because everybody knows that using a full range of motion will give you better gains.

At least, we think we know that. But is there any solid evidence to back up the belief? And does it apply to all muscle groups, to free weights and machines, and to both compound and isolation exercises? The purpose of this column is to analyse the research on key training variables such as load, volume and, of course, range of motion (ROM). But before we put on our lab coats, it’s worth looking at how these studies are done and what they’re trying to show.

Variable results
When researchers investigate training variables, they measure what happens when two different resistance-training programmes are followed by two groups of trainees over a period of time. One group of trainees performs one resistance-training programme and another group performs a similar programme but with a slight difference. Examples of these slight differences might be the addition of an extra set (for more volume), lifting the weights as fast as possible compared with in a controlled way, or spreading the same amount of lifting over a five-day split rather than a three-day split.

At the start and end of the experiment, the researchers take measurements of muscular size. The extent to which one programme leads to a bigger increase in muscular size than the other tells us how important that slight difference is. During the experiments the researchers try to control as much as they can about the programmes. This is so that they can maximise their understanding of the effects of the variables they’re interested in. At a simple level, they encourage subjects to use identical supplementation and eat similar food for their bodyweight. At a more complex level, they try to control other factors of the programmes that are known to affect hypertrophy.

New era of understanding
When researchers study ROM they either measure angular degrees moved at individual joints or linear distance traveled by the weight lifted. It doesn’t matter too much which measurement method is used because ROM is typically defined in relative terms, with one ROM being full and the other being partial.
Researchers first started exploring the effects of ROM in the late 1980s. Unfortunately, in those early experiments, changes in muscular size were not recorded and only strength gains were tracked. Fortunately, in the last two or three years, a few research groups have started to look at how ROM in resistance-training programmes affects increases in muscular size. To date, three really interesting studies have been performed in this area.

Fully armed
When researchers looked at how preacher curl ROM effects biceps size they found that an increased ROM has a positive effect but they also said the difference could have arisen by chance.  The study, published in the Journal of Strength & Conditioning Research in 2012[1]1 compared the effects of partial ROM and full ROM upper-body resistance-training on changes in muscular size. The trainees were young males but they were not familiar with resistance-training. Both groups performed a preacher curl exercise for the biceps, two days per week for ten weeks, as part of a periodized programme. The researchers defined full ROM as 0-130 degrees of elbow angle, where 0 degrees was full elbow extension, and partial ROM as 50-100 degrees of elbow angle. Before and after the ten-week training period, the researchers measured biceps muscle thickness using ultrasound. While muscle thickness in the full ROM group increased by slightly more than the partial ROM group (9.52% vs. 7.37%), statistical analysis showed this difference might have arisen by chance and not as a result of any substantial difference between the two programmes.

Depth of knowledge
The biceps study was followed up by research that found doing full ROM squats led to greater increases in quads muscle thickness than when the exercise was done with partial ROM. The research, published in the European Journal of Applied Physiology in 2013[2] also shifted the topic of investigation by tackling a compound movement rather than an isolation exercise. Again, the trainees were young males and only slightly familiar with resistance-training. Both groups performed a periodised programme using sets of squats to failure and sets not to failure for three to four sets of three to ten reps, three days a week, for 12 weeks.

The researchers defined partial ROM as 0-60 degrees of knee angle (0 degrees being fully extended) and full ROM as 0-120 degrees of knee angle. Before and after the 12-week programme, the researchers measured leg muscle thickness at various sites along the muscle using magnetic resonance imaging (MRI) scans. The full ROM group increased quads muscle thickness to a significantly greater extent than the partial ROM group. The full ROM group also increased hamstring muscle thickness at one site but the partial ROM group did not.

Second leg study
Leg muscle thickness was also shown to improve when doing full ROM exercises over partial ROM in a study that monitored three different lower body moves. A year after the squat research appeared, the Journal of Strength & Conditioning Research[3] published a study that looked into the effects of ROM on lower-body hypertrophy by looking at a combined programme involving the squat, leg press and knee extension exercises. Again, the trainees were recreationally active (but both males and females were tested) and had little if any experience of resistance-training.

Both training groups performed eight weeks of resistance-training, three times per week, using three sets of ten repetitions for the squat, leg press and leg extension. The full ROM group trained through 0-90 degrees of knee angle (where 0 degrees is fully extended) and the partial ROM group trained using 0-50 degrees of knee angle. Before and after the eight-week study, the researchers measured leg muscle thickness at various sites along the muscle using ultrasound. The researchers found that leg muscle thickness increased significantly at all sites in both groups. There was a general trend for the full ROM group to display greater gains in muscle thickness and this trend was statistically significant at some of the sites.

Apply and improve
So, the evidence suggests that you’re right to tut at the guy juddering on the chin-up bar. He clearly hasn’t been reading his journals. It’s also useful that these three studies each looked at different parts of the body, including the arms and legs, considered both compound and isolation exercises and also used both free weights and machines. None of these study characteristics seemed to have a large detrimental effect on the ability of ROM to maximise hypertrophy, suggesting that it is indeed a key factor.

If you want to apply the findings to the way you train, think about building resistance-training programmes around key movements that work muscles through large ROMs. For the quadriceps, squats need to be as deep as mobility allows. For the hamstrings, deadlifts should be from the ground or lower, if possible. For the biceps, curls are likely to be better when performed seated on an incline to increase the ROM in the stretched position than when seated on a preacher bench. Hip thrusts are probably better than glute bridges for building muscular size in the gluteus maximus. In most cases, this might mean reducing the weight a little but the research is clear that this is the right thing to do if your long-term goal is greater muscle mass.

Why ROM works
Exactly why ROM is so important for hypertrophy is difficult to say. It could be because the muscle is under tension for a longer period of time (perhaps leading to greater metabolic stress), it could be because more work is done (after all, physics tells us that work equals force multiplied by distance), or it could be because the muscle is stretched to a greater extent (possibly causing more muscle damage). In reality, it could be any combination of these factors. It’s too early to tell.

Fortunately, we don’t really need to know which biological mechanism is responsible for the outcome to get the benefit. You can just be even more confident that when you are doing full ROM reps that you’re pulling further and further ahead of the guy doing accidental partials.

1. Pinto, R. S., Gomes, N., Radaelli, R., Botton, C. E., Brown, L. E., & Bottaro, M. (2012). Effect of range of motion on muscle strength and thickness. Journal of Strength & Conditioning Research, 26(8), 2140-2145.
2. Bloomquist, K., Langberg, H., Karlsen, S., Madsgaard, S., Boesen, M., & Raastad, T. (2013). Effect of range of motion in heavy load squatting on muscle and tendon adaptations. European Journal of Applied Physiology, 113(8), 2133-2142.
3. McMahon, G. E., Morse, C. I., Burden, A., Winwood, K., & Onambélé, G. L. (2014). Impact of Range of Motion During Ecologically Valid Resistance Training Protocols on Muscle Size, Subcutaneous Fat, and Strength. Journal of Strength & Conditioning Research, 28(1), 245-255.

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