Walk into any gym and you’ll hear personal trainers instructing their clients to use “full range of motion.” They speak of it as if it were as important as
 the weight itself. But is it? After all, bodybuilders who have made it into the pro ranks are notorious for using partials on all sorts of movements. Surprisingly, it is only recently that someone has taken a direct look at this issue in a scientific way.

A couple of universities in Brazil, in cooperation with California State University, published the results of a study that looked specifically at the effects of range of motion on strength and muscle size.

I emphasize muscle size because there have been several studies looking only at the effects of training within a specific range of motion on strength and sports performance. This is the first study, however, that has included muscle size in the analysis.

Forty untrained subjects were placed into one of three groups:

  • Full (15 subjects), Part (15 subjects), or Control (10 subjects). Biceps were trained using preacher curls on a machine.
  • Participants performed a linear periodized routine, with the number of sets increasing from two (Weeks 1 and 2) to four (Weeks 9–10), and the number of repetitions decreasing from 20 (Weeks 1 and 2) to 8 (Weeks 9 and 10). Both groups (Full and Part) followed the same routine for 10 weeks.
  • The Part group restricted their range of motion to the middle 50 degrees of the movement—meaning they didn’t fully extend or fully contract during each rep, but stayed 30 degrees short of full contraction and 50 degrees short of full extension.
  • Weight used was not equal for both groups, however, as the Part group did not have to fully extend, so the amount of weight they were able to handle for the target reps was higher than the Full group could handle.
  • After 10 weeks, the Full group had increased their one-rep max (1rm) by 25.7% above where they’d started.

The Part group had increased their 1RM only 16% over baseline. When it came to size gains, again, Full nudged out Part, but it was closer, with a 9.52% and 7.37% increase in size for Full and Part, respectively.

This difference in size did not reach statistical significance

So what are we to make of this?

If you are a dyed-in-the-wool health club–type personal trainer, you will be saying, “I told you so!” But if you’re a veteran bodybuilder you may hesitate before coming to such a cut-and-dry conclusion that full range of motion is always better than partial.

It is known that most muscle damage, and the growth it produces, occurs in the lower portion of a rep as you approach full stretch.

In this study, the Part group was specifically stopped from going anywhere near even mild stretch. There was no stretch at all under load.

To me, this is the probable cause for the difference in muscle size after 10 weeks using the study’s protocol.

As for strength, performance is specific to the range of motion that you train in, so it is no surprise that the Full group performed better during a 1RM strength test using full range of motion.

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  • Reference: Pinto RS., et al, J Strength Cond Res., 2012 Aug;26(8):2140-5.

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