Partial vs Full Range of Motion for Muscle Growth (Research Overview)

full vs partial range of motion

Up until recently, the scientific consensus was trending towards the idea that a full range of motion is better than a partial range of motion for muscle growth.

A full range of motion indicates you move the joints involved in an exercise through their full potential in that movement.

A partial range of motion indicates you move the joints in an exercise through a select portion of their full potential.

Excluding the new study we’ll assess in this article, there have been 6 studies comparing a full to partial range of motion for hypertrophy.

4 of these found a full range of motion to be better (one, two, three, and four), 1 found no effect of range of motion (one), and the last one found a partial range of motion to be better (one).

Note, this last study finding a partial range of motion to be superior used a partial range of motion technique that kept constant tension on the muscle. In a separate article (coming soon), we’ve detailed this study, along with other studies that evaluated the effectiveness of a constant tension technique (but did not really use a partial range of motion). Moreover, there is a discussion in that article about how it may relate to the upcoming details in this article, so you may wish to read this article first.

The Limitation With the Current Range of Motion Research

So, 4 out of the 6 studies exploring range of motion suggests a full range of motion is better than a partial range of motion.

However, if you were to carefully assess these 4 studies, you couldn’t actually truly conclude that a full range of motion is optimal.

Let me explain.

All of these studies used a partial range of motion that trained the muscle at a short or neutral length.

Let’s demonstrate this by quickly going through each of the four studies.

Pinto et al.

Pinto et al. used a preacher curl, one group of subjects used a full range of motion, from 0 degrees of elbow flexion to 130 degrees of elbow flexion.

Another group used a partial range of motion, from 50 to 100 degrees of elbow flexion. Due to this range of motion, the biceps would have been working at a short to neutral length.

Increases in biceps thickness favored the full range of motion group.

However, what if the partial range of motion group instead used a partial range of motion that trained the biceps at a long length? For instance, what if they trained from 0 to 50 degrees of elbow flexion. Would this still be inferior to a full range of motion?

Bloomquist et al.

The second study by Bloomquist et al. had a full range of motion group perform squats from 0 to 120 degrees of knee flexion.

A partial range of motion group performed the exercise from 0 to 60 degrees of knee flexion, meaning the quadriceps would have been working at a short length.

Increases in thigh cross-sectional area across many regions of the muscle were significantly greater for the full range of motion group.

But again, what if the partial range of motion group used a range of motion that trained the quadriceps at long lengths. For instance, what if they trained from 60 to 120 degrees of knee flexion?

Kubo et al.

The third study by Kubo et al. had a full range of motion group perform squats from 0 to 140 degrees of knee flexion.

A partial range of motion group performed the exercise from 0 to 90 degrees of knee flexion, meaning the quadriceps, adductors, and glutes would have been working at a short to neutral length.

Increases in quadriceps volume were similar between both groups, but increases in gluteus maximus and adductor volume were significantly greater for the full range of motion group.

Again, what if the partial range of motion group used the bottom range of motion in the squat, to train the muscles at a long length. Would the results still be the same?

McMahon et al.

The fourth and final study by McMahon et al. had a full range of motion group perform a range of lower body exercises from 0 to 90 degrees of knee flexion.

A partial range of motion group carried out the exercises from 0 to 50 degrees of knee flexion, resulting in the quadriceps being trained at short lengths.

Vastus lateralis cross-sectional area increases at most regions favor the full range of motion group.

Again, what if the partial range of motion group used a range of motion that trained the quadriceps at a long length. For instance, what if they trained from 50 to 90 degrees of knee flexion?

Partial Range of Motion at Long Muscle Lengths?

So, on the face of it, these 4 studies collectively indicate a full range of motion is better than a partial one.

But, upon closer analysis, they only truly indicate a partial range of motion that trains the muscle at a short to neutral length is inferior to a full range of motion.

They do not inform us of how a partial range of motion that trains a muscle at a long length compares to a full range of motion.

New Research: Partial Range of Motion at Long Lengths vs Full Range of Motion

Fortunately, a new study by Pedrosa et al. does actually compare a partial range of motion at long muscle lengths to a full range of motion.

Protocol:

45 untrained women were assigned to one of five groups: a long length, short length, full range of motion, varied, or control group.

We won’t mention the control group any further. They did no training and, as expected, experienced minimal gains.

All four training groups trained a knee extension machine with a 2-second lifting and 2-second lowering phase, three times per week for 12 weeks.

The long length group trained with a partial range of motion that worked the quadriceps at a long length. From 100 to 65 degrees of knee flexion. The short length group trained with a partial range of motion that worked the quadriceps at a short length. From 65 to 30 degrees of knee flexion. The full range of motion group trained with a near full range of motion. From 100 to 30 degrees of knee flexion.

The varied group, in one session, performed the knee extension identical to the long length group, but in their next session, they performed it identical to the short length group. They continued alternating between these two ranges of motions throughout the study.

All groups trained the exercise each session with 3-6 sets of 7 repetitions with a 60% one-rep max load, using 3 minutes of rest between sets.

The 60% one-rep max load was specific to each group’s range of motion.

Every 2 weeks, one-rep max for each group’s respective range of motion was retested to readjust the 60% one-rep max training load.

Measurements:

Cross-sectional area of the rectus femoris and vastus lateralis was measured at 40, 50, 60, and 70% of the thigh bone length.

Results:

The results indicate the long length group experienced the best muscle growth responses compared to all other groups. But, the varied group was a close second.

Let us further break down the findings more.

Data are mean ± standard error

At 40% of the thigh bone length, increases in rectus femoris and vastus lateralis cross-sectional area were statistically similar between all groups.

But, at 50% of the thigh bone length, increases for the rectus femoris and vastus lateralis were similar between the long length and varied group but greater than the other two groups.

At 60% of the thigh bone length, increases for the rectus femoris and vastus lateralis were similar between the long length and varied group but greater than the two other groups.

Finally, at 70% of the thigh bone length, increases for the rectus femoris and vastus lateralis were greatest for the long length group compared to all other groups.

Discussion:

These results clearly demonstrate that there is a difference between a partial range of motion that trains a muscle at a short length and a partial range of motion that trains a muscle at a long length.

Furthermore, a partial range of motion that trains the muscle at a long length does not appear to be inferior to a full range of motion. In fact, at most measured regions, it was superior.

Training a Muscle at Long Lengths vs Short Lengths

Before we speculate on the reason for the fascinating results in the Pedrosa et al. study, there is other research supporting the idea that training a muscle at a long length is superior to training a muscle at a short length.

A study by McMahon et al. had a long length group train the knee extension from 90 to 40 degrees of knee flexion, meaning the quadriceps were trained at a long length.

A short-length group trained the exercise from 50 to 0 degrees of knee flexion, meaning the quadriceps were trained at a short length.

Cross-sectional area increases for the vastus lateralis at all measured regions were greater for the long length group.

Unfortunately, this study did not have a full range of motion group.

Nevertheless, it clearly demonstrates how a partial range of motion at a long muscle length is superior to one at a short length.

Research on isometric training further supports this.

Isometric training is where you hold a muscle in a static contraction.

A review paper by Oranchuk et al. combined the results of 9 different studies and found that isometric training at a long muscle length produced greater muscle growth compared to isometric training at a short length.

Why a Partial Range of Motion at Long Lengths May Be Superior

So, to return to the core of this video, a partial range of motion that trains a muscle at a long length might be overall superior to a full range of motion.

Why?

There is no certain answer to this question yet.

But, there are a few potential hypotheses.

More Metabolic Stress and Muscle Damage?

Firstly, training a muscle at a long length with a partial range of motion could result in greater metabolic stress and muscle damage.

For instance, one study found that an isometric knee extension at a long muscle length resulted in greater oxygen consumption compared to contractions at a short length. Perhaps implying more metabolic stress.

Additionally, a few studies (one, two, and three) found training a muscle at a longer length resulted in greater muscle damage in the days after training compared to training at a shorter length.

The caveat with these studies is they compared long length partial range of motion or isometric training to short length training, not to full range of motion training.

When compared to a full range of motion, there could still be a difference, but without research, it is difficult to say.

Nevertheless, I believe these reasons are unsatisfactory.

Mainly because the role of metabolic stress and muscle damage in muscle growth is far from clear.

There are numerous lines of evidence that would suggest more metabolic stress or more muscle damage does not result in more muscle growth.

Greater Mechanical Tension?

A much better-categorized mechanism of muscle growth is mechanical tension.

And as it turns out, there might actually be ways in which a partial range of motion at long muscle lengths induces greater mechanical tension.

First, we need to establish what mechanical tension truly is.

Mechanical tension is simply equal to the force generated by a muscle.

A muscle generates force via active tension or passive tension.

Exploring active tension first, this is the force generated by the contractile units of a muscle.

Looking at the layers of a muscle, within a muscle fiber are myofibrils.

Myofibrils are home to the contractile units of a muscle, called sarcomeres.

These generate force when something called the myosin head extends from the myosin filament, and pulls on something called the actin filament towards the M-line, shortening the length of the sarcomere.

A) Resting sarcomere.
B) The myosin heads extend from the myosin filaments and attach to the actin filaments.
C) The myosin filaments pull the actin filaments towards to M-line, shortening the sarcomere length.

The force generated by this interaction ultimately pulls on tendons and results in muscle contraction.

Put simply, there are mechanosensors that detect these very forces, and go on to initiate signaling cascades that result in muscle hypertrophy.

Zooming out, high levels of active tension is a result of two components: muscle fiber recruitment and the amount of force generated by each muscle fiber.

High levels of muscle fiber recruitment mean more sarcomeres in a muscle are generating force, while a high amount of force generated by each muscle fiber means the sarcomeres are producing high amounts of force.

There is some research demonstrating individuals possess greater voluntary activation when contracting a muscle at a long length.

This implies that the body may be able to recruit more muscle fibers and/or produce more force with each muscle fiber when you contract muscles at a long length.

Let me explain further.

Voluntary activation refers to how much of a muscle you can access to produce force.

Generally, no one can actually activate a muscle 100% fully.

Using special equipment, researchers can figure out what percentage of a muscle’s force-producing potential you can voluntarily activate during maximal efforts.

Quite a few studies (one, two, three, four, five, and six) have demonstrated that individuals experience greater voluntary activation during contractions at longer muscle lengths.

As one example, Douget et al. measured voluntary activation of the quadriceps during different stages on a knee extension machine.

When subjects performed a maximal contraction at 50 degrees of knee flexion, their voluntary activation level was 93.6% on average.

When subjects performed a maximal contraction at 75 degrees of knee flexion, voluntary activation was slightly higher, on average 96%.

Finally, when subjects performed a maximal contraction at 100 degrees of knee flexion, voluntary activation was even higher, around 98.5% on average.

So, subjects experienced greater voluntary activation when the quadriceps were at a longer lengths, indicating an enhanced capacity to recruit more muscle fibers and/or produce more force with each muscle fiber.

Therefore, performing a partial range of motion at long muscle lengths may allow you to experience higher levels of active tension for the full duration of the exercise.

When using a full range of motion, your active tension capacity would fluctuate throughout the range of motion. When the muscle is at a long length, it would be able to reach higher active tension levels, but as it moves to a more shortened length, its active tension capacity may slightly diminish.

This fluctuation and inconsistency may explain why a full range of motion could be inferior to a partial range of motion at long muscle lengths.

Aside from active tension, passive tension also plays a role in mechanical tension.

Returning to the structure of a muscle, we detailed how within muscle fibers are myofibrils and how within myofibrils are sarcomeres.

Passive tension is the force generated when a sarcomere is stretched. More specifically, when a molecule within the sarcomere called titin is stretched, it generates passive tension.

A) to B) demonstrates the stretching of titin

This tension is essentially the resistance to stretch.

Like an elastic rubber band, when you stretch it, it resistances stretch.

Furthermore, once you let go, that tension that resisted stretch can snap the rubber band back to its resting shape.

Titin acts in much the same way.

The passive tension generated by titin is detected by mechanosensors which go on to initiate signaling cascades that result in muscle hypertrophy.

Now, one would assume that when a muscle is stretched, so at a long length, its sarcomeres are also stretched, meaning passive tension is high.

However, somewhat confusingly, this isn’t always the case.

A muscle can have its sarcomeres arranged in a way that means when it is stretched, its sarcomeres aren’t stretched to the point of high amounts of passive tension.

Moreover, at a given muscle length, within the same muscle, different sarcomeres may be at different lengths.

Having said this, they’re still likely are muscles, or at least parts of a muscle, that have its sarcomeres sufficiently stretched to the point of amounts of high passive tension when the muscle is at a long length.

Although there isn’t a substantial amount of research in this area, the muscles of the quadriceps do appear to have their sarcomeres sufficiently stretched to the points of amounts high passive tension when the quadriceps are at a long length, at least in the muscle regions measured in the study.

Therefore, using a partial range of motion that works a muscle at long lengths might result in a consistently high contribution of passive tension to the exercise.

Conversely, when using a full range of motion, the degree of passive tension may fluctuate throughout the exercise. It may be high when the muscle is at a long length, but then sharply disappear when the muscle is shortened.

The more consistent passive tension with a partial range of motion at long muscle lengths might further explain why it could be superior to a full range of motion.

So, to summarize this section of the article, it’s plausible that a partial range of motion at long muscle lengths results in greater active and passive tension, making it a more powerful stimulus for hypertrophy compared to a full range of motion.

I should emphasize that these are hypotheses, although I believe they are quite strong hypotheses, future research would need to verify them.

Limitations and Further Considerations

Now, I think it would be useful to close off the article with a discussion on some limitations and further considerations.

Strength-Curves

The exercise used in the main study of this video by Pedrosa et al. was a knee extension machine.

When using a full range of motion on this exercise, the exercise is hardest and requires the most amount of force production closer to full knee extension, when the quadriceps are at a short length.

Therefore, during fatiguing repetitions, the quadriceps are being challenged the most at a short length, not a long length.

In other words, when performing full range of motion repetitions on the knee extension, you are not training the quadriceps maximally at a longer length.

Could this very fact explain why the long length group achieved superior muscle growth?

What if the study used an exercise that, with a full range of motion, required maximal force production at long muscle lengths?

For example, in a full range of motion squat, the exercise is most challenging when the quads, glutes, and adductors are more lengthened than shortened.

Considering this, would a partial range of motion squat at long lengths (so performing the bottom half of the squat) still produce more muscle growth than a full range of motion squat?

This is a question for future research.

Other Muscle Regions

Regarding the Pedrosa et al. study, although it measured cross-sectional area at quite a few regions of the quadriceps, it did not measure everything.

Measurements were taken at 40-70% of the thigh bone length for the rectus femoris and vastus lateralis, but what about 10-30% or 70-100%. Moreover, what about the vastus medialis and vastus intermiedus.

It remains possible, although unlikely, that in these unmeasured regions, the full range of motion, or even the short length group, could have experienced superior gains.

Finally, it’s very important to remember that this is only one study. Replication is important in science.

At the moment, it would not be sensible to truly confirm and conclude that a partial range of motion at long lengths is superior to a full range of motion, future research is required.

Based on your interpretation of this article, you may wish to experiment with partial ranges of motions at long muscle lengths. Ultimately, there probably is no massive or terrible downside.

The future of range of motion research looks exciting, and I look forward to updating this article if any new research comes along.

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2 comments

  1. Hi: Another fantastic article. Love the diagrams and everything explained clearly and concisely. Keep up the great work!

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