Why Do I Shake When I Workout?  

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Written By Kristen
Kristen has been in the fitness industry for over 20 years, providing a variety of personal training services. She has certifications from the National Academy of Sports Medicine and is a NASM - Certified Personal Trainer (CPT).

Although you might be wondering why do I shake when I workout, some folks operate under the impression that if their muscles don’t shake, wobble, and wiggle by the time they’re done grinding it out in the gym they must’ve done something wrong – and their workout must not just have been tough enough to trigger the progress and growth they are after.

And while there’s definitely some truth to that (a grueling workout will almost always leave your muscles shaky), there are a couple of other reasons your muscles might start shake during a workout.

We break down the major reasons your muscles are shaking during workout below.

Why Do I Shake When I Workout

Why Do I Shake When I Workout?

When the core muscle fibers are fatigued and your reserves have to step in to take the place of the other depleted motor units. This is the main reason why your body might be shaking during the workout.

Let’s jump in;

Muscle Fatigue

Muscle fatigue can cause your muscles to shake during a particularly intense workout is simply that those muscles are fatigued – your muscle fibers (each and every one of them) are shot, burnt out, and begging for rest and time to recover.

Every time you work out you are triggering muscle fibers in your body to contract and release. Your muscles work kind of like Velcro – with individual muscle fibers locking up, tearing apart, and then locking up again throughout the workout.

Eventually, your muscles just can’t handle any more contractions and you become fatigued. Your muscles contract a lot less efficiently, and the muscle fibers that continue to try and “fire” they would when fully rested are going to cause your body to shake and sort of shiver.

If you’ve been grinding it out at the gym and really taxing your major muscle groups you’ll have a good idea of when it’s fatigue causing the shakiness. This is a surefire sign that it’s time to dial the intensity back and maybe even cut your training session short.

New Muscle Tissue Getting Recruited for the First Time

All of our major muscle groups strive for a sort of homeostasis in the body, with muscles that are developed to the level that they are being used and trained.

Muscles that haven’t been trained or worked out at all (or even just in a while) are mostly made up of relatively virgin muscle fibers, muscle fibers that haven’t had to stretch, contract, tear, and grow bigger and stronger.

These muscles are going to fatigue a whole lot sooner than muscles that have been trained over a few months or even a few years – and that’s going to lead to shakiness.

On top of that, it’s not at all uncommon for “support muscles” that get activated during major compound lifts (smaller muscle groups that get worked out alongside larger muscle groups) to fatigue pretty quickly and start to shake and shiver as well.

The only way to resolve this kind of shaking is to keep training (smartly, but consistently) to get those muscle groups trained up to handle your workouts.


Dehydration can be another root cause issue that causes you to deal with your muscles shaking and shivering.

As you work out you’re going to be putting a ton of stress not just on the individual muscles that you’re working out, but the rest of your body in general – including your central nervous system.

You’ll trigger a cascade of different hormones to release throughout your body, change the level of electrolytes you have, and cause different chemicals to flood into your muscles or to be pushed away from them.

If your body isn’t properly hydrated you are going to really throw yourself for a loop. It’s not at all uncommon for the connective tissue in your body (as well as your actual muscle fibers) to start to stiffen and lock up as they become more and more dehydrated during the workout.

Sip water consistently throughout your workout, though, and this will be a lot less of a problem for you. Properly hydrate before and after your workouts and you won’t have to worry about this kind of shaking at all.

Caffeine Levels Too High, Blood Sugar Too Low

Caffeine levels that are too high or blood sugar levels that are too low can contribute to your muscles getting shaky during or after a workout.

A lot of popular pre-workout supplements include a pretty hefty dose of caffeine, sometimes a dose that goes well above and beyond the daily recommended amount from the FDA (400 mg).

If your body is not used to that amount of caffeine – especially when consumed in a super short period of time – you run the risk of caffeine causing you to be twitchy, shaky, and jittery.

On the flip side of things, if your blood sugar levels are low (something that can definitely happen during the cascade of biochemicals and hormones triggered by lifting heavy things or physically exerting your body beyond what it’s used to) you’re going to feel twitchy, shaky, and jittery as well.

A quality pre-workout supplement, one that has a bit of caffeine (but not a ton), as well as lots of water before you work out should help to even out your caffeine and blood sugar levels significantly.

Related: Why Does My Body Shake When I Work Out?

Closing Thoughts

At the end of the day, you really have to listen to your body to determine exactly why your shaking, wiggling and wobbling during and after your workouts.

You may be dealing with a workout program that’s a little too intense or a little too much for your body right now. You might be dealing with muscle fatigue issues or are targeting new muscle groups and just need a little more rest and recovery before you get back into it.

Of course, you might also be running in a dehydrated or over-caffeinated state (two things that are relatively easy to iron out drinking more water and being careful about your pre-workout supplements).

Regardless of the reason for your shakes, though, it’s important that you accurately diagnose the issue, take the right steps to remedy the situation, and understand the difference between normal shakes following a tough but solid workout and shakes that are signs that something needs to be dialed back ASAP.

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Written By


Kristen has been in the fitness industry for over 20 years, providing a variety of personal training services. She has certifications from the National Academy of Sports Medicine and is a NASM - Certified Personal Trainer (CPT).