Why Does My Body Shake When I Work Out?

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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).

That final rep. One last push and then you are done. You feel your body shaking, and usually, it continues as you try to leave the gym. The jelly legs are in full effect and every push of a door feels like another workout. But why does it happen?

The shaking you feel whilst working out is essentially different groups of your muscle fibers contracting and relaxing simultaneously, which is normal when putting your muscles to work!

Your body does strange things during a workout, so much happens that we don’t realize. It’s a funfair of chemical reactions, biology and a lot to do with what you put in your body and when you do so!

Read on to find out why this happens as well as what to do when your body shakes working out.

why does my body shake when i workout

Shaking Is A Chemical Reaction?

A Lot Can Happen In Your Body During A Workout, chemical reactions being one. Chemical reactions are constantly occurring and messages are sent all over your body. Every single muscle in your body will get different instructions and every fiber within those muscles is told by your brain to do a multitude of things at different times.

It all comes down to nerves and muscle fibers. Motor neurons essentially carry messages from the brain through the spinal cord to individual muscle fibers. These muscle fibers are divided into different groups so as not to be working all at once.

The chemical reaction which sends the messages from the brain to the fibers fundamentally tells the parts of the muscles to contract and help complete the rep. The other fibers in the muscle now relax.

Imagine a room of 100 people, 50 sitting down and 50 standing up and constantly swapping positions. This is what your muscles do, as you become more and more tired your brain sends more messages to your muscle fibers, thus moving from a relaxed state to a contracting state. This creates a twitch, and in turn causes the shaking of the muscle.

Will This Always Happen When I Workout?

This doesn’t always happen, of course, it depends on the intensity of your workout and whether you’re using a group of muscles you haven’t used for a while. So, the more prone you are to working out the fewer shakes you’ll get! As you exercise more, your muscles become used to the labor and can better handle the workload.

By increasing the number of reps you do, or changing your workout, your muscles will go beyond their usual capacity and more than likely begin to shake again. This isn’t a negative thing, the shaking usually means you’re pushing yourself past your usual limit and excelling!

You’re fulfilling your gym goals, working harder and harder each time means your muscles are growing and are able to do more. Don’t put all your time working on one thing though, if you concentrate on one exercise for a while your muscles may be comfortable and not shake anymore. But your other muscles will when you return to them.

This is why you often we people alternate workouts. In the same week, they will train two or three different areas as this makes sure no muscles are neglected and won’t hurt when you return to them. This explains why it’s better to do different workouts every day as opposed to a full week of doing only one exercise.

So Is It All About How Much Work I Put In?

It can be other things too. Hydration plays a huge part in a workout, and a lack of hydration can cause shakes. Even just a loss of one/two percent of fluid from your body through sweat can affect the flow of blood around your muscles. The slowing of blood around your body means essential nutrients, such as electrolytes don’t reach the working areas as quickly as required.

This hydration issue is easy to combat though, as well as drinking the recommended eight glasses of water a day, make sure you’re drinking small amounts of water during exercise to replenish the water you lose through sweat. Of course, drink more when it’s warm too. Sports drinks also come in handy, offering extra nutrients for your body whilst it works hard.

What About Those Post-Workout Trembles?

Shakes can often occur after working out, too. Again, these are usually nothing to worry about and can be easily explained and sorted out:

Hydration can again be a reason for having the shakes after working out. Again highlighting the importance of replacing all lost fluids even after the conclusion of your session. Sports drinks are the best bet as they also contain sugars which could be another reason.

Low Blood Sugar is a common after-effect of physical training. It can happen whether you’re diabetic or not! Sweating leads to your body frantically trying to replenish sugars which can lead to hypoglycemia. This can cause shaking, weakness, and even confusion. Many isotonic drinks contain sugars that will help hydrate you and refill you with necessary sugars.

How to Avoid Your Body-Shaking During Workout

Before working out, if you want to avoid your body shaking, it is best to avoid caffeine. Coffee and other caffeine-filled beverages can really dehydrate you and may cause you to shake.

Never eat right before a workout, moving around excessively with a full stomach will be uncomfortable and could lead to you being sick.

Don’t jump straight into a heavy workout. Your body won’t appreciate going from 0-100 miles per hour so quickly, it’s important to get your muscles ready. A warm-up will help get the blood flowing beforehand, and a cool-down will help save you from sore muscles after.

Related: Why Do I Shake When I Workout?

In Summary

Basically, your body shaking during a workout is due to muscle fatigue, dehydration, and/or from subjecting yourself to a new exercise. It is usually not something to worry about, replenish your fluids to make sure you are fully hydrated, don’t push yourself too hard, and work hard but within your means.

Get yourself properly ready for your workout by avoiding eating food right before. Prepare yourself by warming up.

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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).