You're holding a plank, minding your own business, when all of a sudden, your muscles start to quiver and shake like a scared puppy.
It can be a disconcerting feeling and sight, there's no doubt about that. The question is, what does it mean?
There are two answers, one simple and one complex, but both true. The simple answer is that your muscles are working hard and becoming fatigued, and may not be used to working in the way that you're working them. Makes sense on the face of it.
The complex answer has to do with your nerve cells, specifically the ones that make your muscles work.
These cells work hard to try to maintain equilibrium in the muscle and in your body. Some muscles contract while others lengthen in order to create orderly movements.
When your muscles are under duress---during a plank, for example---this is still happening. Some muscle fibers are firing while others are relaxing in an attempt to help you maintain the plank position you're going for.
As muscular fatigue increases, this "on and off" action in the muscles becomes more pronounced and erratic. The neural messages aren't being delivered as efficiently because the muscles---and the nerves that control them---are under duress, eventually resulting in that familiar but not-so-comfortable shaking feeling.
The next question is, what causes the shaking to be better or worse? An obvious and easily fixable contributor to muscular shaking is dehydration. Muscle fibers function in a fluid environment, so dehydration exacerbates inefficient muscular function. A muscle without water is like an engine without oil. So drink up!
New exercises that have never been tried before can also result in muscular shaking simply because new muscles are being used with which the nervous system doesn't have a super-strong connection.
Additionally, shaking is an indicator that an exercise---often a new one--is being pushed too far or for too long than is appropriate, and that a more graduated approach may be necessary.
So, when it comes to shaking, should you be concerned? In general, muscular shaking is nothing to be worried about, but rather to be mindful of. For one thing, drink more water.
For another thing, you are not in danger when you experience it during exercise, and trying to totally avoid it makes it harder to progress with an exercise like a plank.
The best approach is to work with your trainer and establish at what point the shaking becomes uncomfortable. Does it happen before or after the muscle group you are working on becomes fatigued?
Let's take a plank for example. Does the shake become unbearable before your core muscles are tired? If this is the case, it makes sense for your trainer to regress the exercise---maybe by putting your knees on the floor during the plank-- so that you can hold the core contraction long enough for it to become fatigued.
Does that make sense? In order to progress, the exercise must be challenging. That's the important part. But if you can stand some shake and want to push yourself further, a little bit won't hurt.
However, reaching the point of shaking with every exercise is not necessary either. As is the case with muscle soreness, muscular shaking is not necessarily a marker of greater success, the absence of which suggests you didn't push yourself hard enough. So don't go too far in that direction either!
I hope this article has helped clarify the causes, importance, and strategies of dealing with shaking during exercise. Now drink some water and let's get shakin'!