How muscles are like onion bags

Posted on May 4, 2018

(Last Updated On: May 4, 2018)

I was listening to an interview with Tom Myers of Anatomy Trains. He used an analogy that really hit home for me. One of relating muscles, and the fascia they are connected to, to onion bags.

Picture an onion bag, then picture it in the shape of a diamond:

Muscle fascia

The bag (muscle/fascia) can either be pushed or pulled by the left and right sides, or pushed/pulled by its top and bottom. Based on the initial action there will be a reciprocal action.

For example, if the left and right are pulled apart, the top and bottom are “pushed” together (or vice versa). Or say the left and right are pushed together, then the top and bottom are pulled apart (or vice versa).

Here are some high tech drawings to help with visualization:

Muscles fascia manual therapy


Muscles fascia massage

Using the netting of a onion bag to help with visualization, you can see how doing this over and over again can cause the muscle to become either chronically stretched or chronically short.  Based on the condition of the muscle, that is whether it is chronically long or short, we form a treatment.

If it’s long, get it to shorten. If it’s short, get it to lengthen.

For me, this typically meant exercising the long muscles and getting them stronger in order to hypertrophy them, thus tightening them up. This is then accompanied by some manual therapy on the short muscles to loosen them up, as well as various exercises that emphasize stretching the short tissue.

However, what hit home for me was Myer’s comments regarding manual therapy work on the long muscle. Something I never considered as I’ve always thought of manual therapy primarily as moving with the grain of the muscle to help lengthen it.

Going back to our bag analogy, here’s how manual therapy can be used:

Let’s use the bicep as an example:

bicep pain

So, picturing the bicep as an already stretched out diamond shaped onion bag, if we flex the bicep the top and bottom of the muscle/fascia come closer together. Thus, the top and bottom of the onion bag come together, which means the left and right sides of the onion bag (biceps) move apart from one another. The muscle bulges laterally as it contracts.

Therefore, if we have someone with a chronically tight bicep, manual therapy along the grain of the muscle, that is, going up and down the muscle in this case, will help push the top and bottom away from each other. Again, when the top and bottom move away from each other, the left and right will come closer together. Voila, we lengthen the muscle.

However, what if the bicep is chronically lengthened? Again, using our bag analogy, the top and bottom of the bicep will be pulled away from each other. Therefore, the left and right will be pushed closer together. So, using manual therapy against the grain of the bicep (in a left and right motion) will widen the bicep.

Push the left and right sides away from one another and the top and bottom will be pulled closer together. Voila, the bicep is shortened.

Why is this important?

One of the mistakes I see people make when it comes to using foam rollers or getting a massage is blindly rolling or massaging the hell out of EVERYTHING.

When one muscle becomes shortened often times another becomes lengthened. But often times it seems when people get a massage or use a foam roller they assume everything is tight. (Just because something is tender when rolling it does not mean it’s tight!)

CRITICAL POINT: Trying to lengthen muscles that are already lengthened can and likely will make whatever you’re trying to make feel better…feel worse. Something can be too stretched.

Back to our beloved bag analogy and bicep example: If the bicep is lengthened, the top and bottom are pulled apart and the left and right move closer together. If some form of manual therapy is implemented which worked with the grain of the muscle, that is, if we pushed the top and bottom further apart from one another, the left and right would come even closer together. Thus, we would lengthen the bicep even further! Not helpful.

Note: This isn’t a common issue with the bicep but I use it because it made for an easy example.

Next time you perform some form of massage on yourself or you receive one, ask yourself what you’re trying to accomplish by working the specific muscle you’re working. AND if the direction you are working the muscle/fascia is the proper one.


For more on Tom Myers check out the Anatomy Trains book.


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Posted in: Pain