The new science on stretching the lift all the way out: Long-Length Partials

Author: Scott Morris, Fitness Expert

Put the muscle under MORE stress

I have talked so much about how to build muscle on this website as it is just one of the things that fascinates me most in life. I have spent a lot of time in the gym and maybe more time reading the scientific literature around it.

What I can say is that it appears that there have been some breakthroughs in the science behind muscle building just over the last few years, and it seems that the body builders of the past are kind of saying “we told you so.” It really comes down to what is called a partial and full range of motion rep.

What is a partial?

The goal in muscle growth is muscle stimulation, right? We are trying to get that muscle under load for the longest time (time under tension) for as many reps as possible before failure (reps in reserve), right?

Decades ago, the theory was that gym goers would shorten the lift mechanics to just the middle part of the lift to give even more stimulus to the muscle. It allowed the lifter to lift more weight for more reps, therefore getting more time under tension. These short reps were called partials because in the 180 degrees of the lift, one would only use part of that, say just 100 degrees somewhere between 40 and 140 degrees.

But, according to some fascinating recent studies, stretching it out is turning this midrange partial on its head (it was probably always just a theory with no real science behind it). In other words, if you’re doing a partial that doesn’t include the bottom part of the lift, you may be behind the times. Recently, the science is showing that when the muscle is stretched all the way out, the muscle is stimulated the most.

Here’s a good example of this. Just consider the bicep curl. Many lifters will stop just before the bottom, even if they are doing a full range of motion lift. They will cut off the bottom 10% or 5% and then start back up again.

Right now one of the most exciting aspects of lifting focuses on what's called the "long-length" portion of the lift or the portion of the lift when the muscle is stretched all the way out. Jeff Nippard describes it best here. Let me note here that the “long-length” portion of the lift is a little different for each muscle group and doesn’t always mean that the joint is all the way stretched out. An example of that would be the tricep, which needs to have the elbow bent (not straight out) as much as possible in order to get the muscle in its “long-length” position.

So why did people do Mid-length partials to begin with?

There may be many reasons why someone is cutting off their lift before they reach the bottom. We discussed one earlier. Some focus there because they think that will build muscle faster, but my opinion on this is that the real reason people do mid-length partials is because they are just easier. You get to do more weight (kind of sexier) and it just feels better (no putting the joint in an exposed position).What they are leaving on the table, however, is the biggest stimulus to the muscle. 

Why don’t more people do it? 

It is hard. When the muscle is stretched out in full range of motion, it is hard to move the weight. Literally the muscle has a harder time moving weight at that part of the lift because the muscle is actually weaker there. So when you push into this much more difficult area, you are asking the muscle to do more.

And this is exactly why you should do it and the science agrees with me. Those who get their muscles to stretch out as much as possible, see greater muscle stimulation and growth. There are two studies that you should look at if you are interested in the science. “Muscle activation differs between partial and full back squat exercise with external load equated” and one called “Muscle architectural adaptations to knee extensor eccentric training: rectus femoris vs. vastus lateralis.”

Here’s my tip:

In order to get the most out of your lift, you need to think about stretching the muscle all the way out. The science is showing that the muscle gets more stimulus here. You may need to do drop the weight just a bit. Don't feel bad about this. You will make more gains by getting the movement right because you'll get more stimulus on the muscle. What I have seen is the muscle gains strength in the most critical part of the movement and that provides the best foundation for amazing strength and muscle growth.