Why do muscles shake during a workout? Is it really a good thing?

If you’ve ever done a barre fitness workout, you’ve probably experienced the ‘barre muscle shake’ or heard the term ’embrace the shake’ from your instructor?! But I’ve wondered why should I embrace it? Is it really a good sign? So I’ve done a little research and here’s what I found out about why our muscles shake during a workout, especially during a barre strength training.

Compound vs Isometric movements

First thing first, in order to understand this shaking phenomena when we exercise, it is helpful to know that there are different types of moves and muscle fibers that are activated when we contract our muscles.

Compound high intensity exercises such as squats, burpees, arm extensions and push-ups, make you move your joints through a full range of motion. These traditional resistance trainings mainly activate type II muscle fibers, also called ‘fast-twitch’.

 Fast twitch fibers contract quickly and powerfully but fatigue very rapidly, sustaining only short, anaerobic bursts of activity before muscle contraction becomes painful. They contribute most to muscle strength and have greater potential for increase in mass. 


Barre fitness low intensity style workouts mainly focus performing isometric exercises which isolate and contract specific muscles. By using one part of the body while keeping the other still, there is very little to no joint movement. Planks, holding still on a single leg, doing little pulses; these isometric tensions activate type 1 muscle fibers also called ‘slow-twitch’ muscle fibers.

When you pulse and hold a certain position, you lift only using your bodyweight as a resistance.

Slow twitch fibers contract for long periods of time but with little force. 


For instance, every day we use these type I fibers when we stand or walk, by maintaining our posture and joint position.

3 most common reasons why our muscles shake.


New exercise

When doing a new exercise, our body has to learn how to coordinate this new movement. It is through repetition that the body learns how and when to contract the muscles at the right time. Our muscles shake because they’re a bit ‘clumsy’ at first, not quite familiar with the new exercise pattern. The more the brain is acquainted with the movement, the more the communicating nerve cells’ signals are competent.


You never hear it enough: drink drink and drink! Water of course… ;D

When we are dehydrated and exercise, our blood flow reduces/slows down and our muscles end up not receiving the right nutrients they need to keep on contracting correctly. That is why dehydration induces muscle twitching.

Furthermore, sweating impacts our performance by reducing our ability to exercise. That is why we need to drink at least 7 glasses of water per day and when we workout, sip water throughout the session.

Muscle failure

When we contract our muscles, it is our nervous system that sends chemical signals via motor neurons (nerve cells) which tell the muscle fibers (low-twitch and fast-twitch) to tighten.

Muscle fatigue occurs when we work our muscle fibers to exhaustion. One of the signs is shakiness, notably during barre workouts. When you do an isometric exercise (isolating and working on a specific muscle) and you perform may reps of this same exercise (little pulses for instance) or hold a position for a longer time (30 to 60 seconds), that’s when you can experience uncontrollable trembling.

The muscles start quivering because the nerve cells lack of energy to keep on sending nonstop contraction signals to your muscles. The muscle contractions being interrupted, become less effective.

When working out a muscle over and over again for an extended duration of time, the supply of glycogen (stored carbohydrates) gets drained.

Moreover, we start feeling the burn, when a process called acidosis occurs in the bloodstream. When our supply of glycogen is all used up, hydrogen ions and lactate are produced, increasing the acidity of the blood and provoking the burning sensation. That is why we may feel sore after a hard workout.

In opposition, when you perform a compound exercise, you activate multiple muscle groups. The load and energy used is shared. You’re not draining one particular muscle’s glycogen supply. The muscles fatigue more evenly.

Is it good to ’embrace the shake’?


I’ve come upon divergent opinions that left me quite confused at first.

On one hand, some say that when you start shaking, you should stop or reduce in intensity because when your muscles weaken, they are more prone to injury. If you are shaking the entire time, that means your workout is too tough and you need to quit or work on another muscle group.

On the other hand, others encourage you to go past your comfort zone and push through the trembling because the main goal in strength trainings is to get stronger. By damaging muscle tissue, the body regenerates more vigorous ones. Overtime, your muscle fibers become more tired-resistant.

Also, the more forceful your workout is, the more calories you burn. However, you need to take the time to recover and feed yourself properly after each session.

So this is what I have come to understand. Muscle overload triggers muscle change for the better. As a result, you get stronger and physically toned. My advice is that you should be careful not to get injured. If you push through the shake (within reason), pay closer attention to using proper form. As long as you listen to your body, sip water regularly and breathe during class, you’ll be OK.

Bottom Line

Now I am less worried when I start shaking. I know it is a good sign. As long as I am doing my workout properly, I understand that I stimulate my muscles enough to change them for the best! And no matter how strong I become, embracing the shake will always be effective to tone up my physique!

What about your experience? Please, do share your comment below. Thanks!

The Fit Yourself Barre content is provided for informational purposes only. It is not intended as a substitute for the medical advice of a physician. You should not take any action before consulting with a healthcare professional.

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  1. Cynthia says:

    Hello! Thank you for the great article. I love that you discuss this topic because a “shake” can be often misinterpreted as a bad thing or an excuse to stop training!  I personally feel like it just shows you are wroking hard or working a weaker muscle. My general rule of thumb is : if you feel no pain (i mean a pain that can lead to injury), you are good to go. Of course, if you feel faint or weak, you are right, there may be dehydration or fatigue. 

    I think as we start to work out often, we know how to understand and interpret what our body is trying to tell us and we just need to LISTEN.

    1. Anne-Caroline says:

      Hello Cynthia, I agree with you, the more we workout, the more we know how our body functions and reacts, the more we learn how to listen to our body! Thanks for your comment!! 🙂

  2. Rashaad says:

    Hello Anne-Caroline. I am really happy to come across this post. Every time I complete a workout, it feels like my muscles are shaking and I was never quite sure why it was happening. Sometimes I thought it was just me. Thank you for breaking it down into all the details and making it easy for me to understand. I will have to share this with my workout buddies!

    1. Anne-Caroline says:

      So glad this article helped you understand what the shake is all about!! Thank you for sharing your experience ;)!

  3. Digital Training Expert says:

    The topic is a fun and an informative article answering the question we all want the answer to. Why do our muscles shake during a workout? Well, the article proceeds to inform you as to why this happens and how it should be embraced as quoted by your instructors.

    The three main reasons are well explained and offer food for thought.

    Barre fitness low-intensity workouts have got me curious about what it’s all about. This blog has certainly helped me to understand that its a low-intensity style workouts isolating specific muscles.

    Having read this article about the type of exercise, I would now consider trying it to see if the feelings are as described in this article.

    1. Anne-Caroline says:

      So happy the article introduced you to barre fitness and what it is all about! Yes you should try it indeed ;)!

  4. David nelson says:

    “Strenuous exercise causes some of the motor units to drop out of service because of fatigue; it is this process that is ultimately responsible for the trembling you observe. … After adequate rest, the fatigued motor units return to normal, and the muscles again appears to produce smooth contractile motion.”

  5. Darren says:

    I think it must be good to have a mixture of fast twitch and slow twitch muscle fibres to cater for different situations? 

    When my muscles shake I always thought it showed that they were working. I was very  interested to read about the different ways our bodies react to isometric and compound movements.

    I haven’t heard of Barre workouts before, it certainly sounds like something I would like to try. 

    1. Anne-Caroline says:

      That’s right, it is good to have a mixture of both! Thank you 🙂

  6. Kirkman says:

    Hello i must say that i am amazed at this website. There is so much attention to detail and this article that you have created on common reasons why our muscle shake is insightful. Muscle failure is one major reason and this is due to exhaustion. Thank you so much for this helpful post!

    1. Anne-Caroline says:

      Thank you! I am so happy you like my website and that you found my article helpful! 

  7. wilson kume says:

    wow what a lovely post we have here written by you,embracing the shake! Actually i always thought that the shake comes due to dehydration but later on i also noticed that it wasn’t just water,i noticed that whenever i start new routines i always get the shake. I just presumed that probably my muscles were weak,so thanks for the good work at least it cleared my doubts.

    1. Anne-Caroline says:

      So happy to know that my article helped you clear your doubts!! Thank you!

  8. Thanks! I started doing some barre workouts and I was really surprised at the shaking! Interesting and comforting article!

    1. Anne-Caroline says:

      Many thanks; so glad you found it interesting!

  9. Hello Anne-Caroline,

    What a wonderful site.

    I have been trying to exercise daily . And I have occasionally noticed my muscle shake. And was a bit worried about it. Thank you for putting all my concerns to rest. I have been doing a lot of new exercises I learn from YouTube, and that might be the cause.

    1. Anne-Caroline says:

      Thank you for your comment and interest! So glad to hear that the article helped understand why you shake during your workouts!! New exercises definetly cause the shakes!

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