Why Am I Shaking During Exercise?

Finding your muscles shaking during your sweat session? It means more than you think!

Experiencing shaky muscles during a workout is typically thought of as a badge of honor for a workout well done or as a sign of building strength. But, shaking can also mean you’ve gone too far.

Taking note of your body’s response to a particular exercise, especially if you’re a beginner, helps you stay in tune with your physical fitness, and make adjustments on the fly.

Let’s dive into the six most common reasons your muscles might shudder, from a HIIT workout to a treadmill run, and what you should do in response.

Reason #1: Fatigue

“Muscles shake after a hard workout as a physiological response to fatigue,” explains Aaptiv trainer Jaime McFaden. “It is usually a great indicator that you have reached your maximum intensity, as well as a good way to know it’s time to back off.”

When your muscles shake, they are challenged, so they start contracting and releasing at an intensified pace. This is normal, and not a problem as long as you aren’t pushing too far past that point. McFaden says lots of people want to build muscle, but are afraid of reaching that “shake” point. Instead of powering through it, aim to reach that point and then take a break.

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Reason #2: New or Different Muscle Groups

You already know the value of switching up your workouts on a regular basis. When you work different muscles, you may encounter shaking. Again, this is completely fine as long as you’re aware of your form and not compensating anywhere else. For example, if you’re holding a high plank and feeling a lot of tension in your shoulders and neck as your arms rattle, it could mean you need to engage your core, so you can avoid potential injury to your low back or rotator cuff.

Change the classes you complete and introduce an assortment of exercises. This way you give your body a break and no muscles end up overworked. So, if you’re loyal to your elliptical sessions, try to factor in time for yoga or strength training to balance out muscle groups. Then you’ll know any related shaking is a result of variety!

Work different muscle groups with our classes. Aaptiv has many different workout categories for you to choose from.

Reason #3: Dehydration

Another common cause of muscle shake is dehydration. When your body is low on fluid, this not only causes a wave of change in your electrolytes, but also your connective tissue experiences difficulty sending signals from your brain to your muscle fibers. In other words, your body gets totally thrown off. So, be sure to sip water for any workout longer than 60 minutes and stay hydrated throughout the day. Here some foods that will help.

Reason #4: Lack of Sleep

Sleep plays a vital role in your ability to perform any type of workout efficiently and effectively. Sleep allows your muscles to heal and rest. “Both lack of sleep and lack of rest [giving your muscles a break in the form of rest days] can cause the body to shake from sheer exhaustion,” says Mcfaden.

If you’re experiencing continuous muscle shake, consider how many hours of sleep you’ve recently gotten. If the number is low, it’s probably wise to catch up on ZZZ’s and skip a workout.

Reason #5: Going Too Fast, Too Soon

In most workouts, it makes sense to push yourself hard. But when you find that your muscles are shaking quite a bit, you may be overdoing it. Additionally, reaching your max in every single exercise can create a sense of going too fast, too soon, which easily leads to poor form—and you guessed it, an increased risk of injury.

“When you notice muscles shaking during a workout, it is best to back off,” says McFaden. “Move on to another muscle group and get some water. The shaking can also lead to injury so you really need to pay attention, and listen to your body.”

The next time you’re mastering the stairclimber and feeling your legs shake, make sure you’ve got good control. Your workout should be tough, but not so hard you’re shaking the entire time. And when muscle shake happens, view it as an opportunity to slow down for a moment or give yourself a short break. (Trust us, the research gives you full permission.)

Reason #6: Ego

When you’re constantly bombarded by images of perfectly toned people absolutely crushing their workout, it’s easy to assume you’re being weak unless you push your body to the max nonstop. But McFaden says pride is a key culprit in terms of muscle shake creating a problem.

“As a personal trainer, I push my clients to shake, and then once they reach that point, back off,” she notes. “Some want to push past the shaking part, and I advise them not to do that, as it compromises form and puts you in a position for muscle imbalance and potential injury. That [desire to shake] can be the unfortunate result of someone’s pride.”

Overall, it’s fantastic to push yourself hard during a workout, but pay attention when your muscles begin to shake, make sure you can breathe, add rest days to your exercise routine, and remember to drink water throughout exercise.

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