Fitness Tips

Why Do I Shake When I Workout?

I’m sure you’ve experienced it before – that dreaded moment during a workout when your muscles begin to tremble and shake uncontrollably. It’s like an earthquake in your body! But why does this happen?

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The most common reason for this is simple and harmless: when we work out, our bodies use stored glucose and ATP (energy) to make the muscle fibers move and stretch. But as energy reserves dwindle and fatigue sets in, more muscle fibers are recruited to take over for their exhausted counterparts. Your muscle fibers oscillate between a relaxed and contracted state, resulting in quivering muscles.

You probably find that shaky muscles occur mostly in large muscle units, like your legs, when you’re doing strength training workouts that involve heavy weights.

But don’t worry, this shaking and trembling isn’t necessarily a bad thing – in fact, shaking muscles can be a sign that you’re pushing the envelope on your body’s capabilities which is when growth happens. That said, everyone has their limit! So if you find yourself shaking so much that you find it hard to stand, then chances are you pushed yourself too hard.

Of course, there’s a little bit more to it than that and other reasons for shaky limbs that are less benign. For example, if your shaking is accompanied by chest pain or any other body pain, dizziness, seizure, shortness of breath, vomiting, etc., you need to see a doctor ASAP!

Let’s explore the various causes of this phenomenon and how to avoid those pesky trembles next time you hit the gym.

Related: 9 Signs You Are Gaining Muscle – Even if You Can’t See it Yet

Top Reasons Why Your Muscles Shake During or Post Workout

Muscle Fatigue

This is the most common reason and the one we covered already. This is the “good” kind of shaking that just means your muscles are fatigued because you have worked them harder than usual.

For instance, if you have challenged yourself with a more intense workout program than you’re used to, you will likely develop minor muscle shaking.

Fatigue from strenuous physical activity causes parts of the muscle’s framework for contracting and relaxing to fail. Muscle movement becomes less seamless as motor units rest. When your endurance threshold falls, your muscles start burning more energy than necessary.

You may begin to shake as a result. So, if you can’t do the same number of reps and sets or you’re in pain while working out, it’s time to take a break or lessen the intensity of your workout.

Dehydration and Hunger

The human body comprises 60%–70% water, and dehydration occurs when only 5% of the fluid is lost. At 15%, the situation becomes critical. Staying hydrated is a must, and it can be dangerous if you don’t drink enough water before you work out.

When dehydrated, your muscles will wobble for sure, but that will be the least of your worries.

Athletic performance suffers as body temperature and heart rate increase proportionately with fluid loss. Dehydration inevitably slows down your body’s natural cooling system, making you more likely to get heatstroke, seizures, or urinary problems.

Similarly, not eating before a workout may cause shaking. Hunger forces your body to conserve energy while giving you signals that you need to eat. When you’re hungry, shaking is a clear sign that you don’t have enough energy to keep doing what you’re doing at the same level of intensity.

Too Much Caffeine

One thing this stimulant does is help the central nervous system “wake up,” causing a temporary rise in energy, blood pressure, and heart rate. With the wakefulness comes an “increased” exhaustion threshold, and sometimes this causes people to overwork their muscles unknowingly. This alone can cause shakiness during exercise.

Caffeine is a stimulant, which means that too much of it will make you feel bad, especially if your body is sensitive to it. While studies show that healthy adults can safely consume up to 400 mg of the substance daily, it is essential to know that tolerance levels differ.

Remember that coffee is not the only culprit! Caffeine is also abundant in chocolate, energy drinks, sodas, tea, and even some medications.

One sign that you’ve had too much of the stimulant is that you feel shaky even before you start working out. Other side effects include anxiety, diarrhea, headache, insomnia, muscle spasms, anxiety, nausea, restlessness, twitching, and even involuntary muscle contractions and relaxations.

The stimulant is also a diuretic, which means you’ll feel the need to pee more often. (Excessive urination can also lead to dehydration over time.)

Medical Disorders

While life-threatening factors do not cause most instances of occasional trembling, shaking can be a symptom of several diseases. Worse, if the trembling worsens over time and occurs even when not engaging in strenuous exercise.

Brain damage, Hoffman’s syndrome, kidney or liver failure, Parkinson’s disease, and other medical issues and diseases can cause shaking. Certain medications and lifestyle choices can also increase the risk of muscle tremors. Amphetamines, antidepressants, corticosteroids, excessive alcohol consumption, and drug or stimulant abuse are among them.

Pay close attention to your body’s symptoms – if you have any inkling that your tremors are linked to a health issue, be sure to seek professional medical assistance right away.


Hypoglycemia, aka “low blood sugar,” is quite uncommon in otherwise healthy people, so feeling shaky during or after exercise is probably not caused by low blood sugar. However, it is possible.

The body stores glucose and sends it to the muscle fibers to get energy when needed. Exercise, regardless of intensity, raises your heart rate, and because you burn glucose in the process, your blood sugar levels begin to drop.

The more fuel burned, the more one’s blood sugar level drops.

Over time, if you fail to replenish the lost sugar by sticking to a meal plan that suits your workout routine, you may develop a condition called hypoglycemia, and your body will no longer have the tools to send enough ATP to the muscle cells. As a result, you may begin to shake because your muscles can no longer contract and relax normally.

How to Prevent Shaking During and After Exercise

Stay Hydrated

Start by drinking 16-20 ounces of water or a clean sports drink before you start your workout. Throughout your exercise, consume 8-12 ounces of water every 15 minutes and an additional 8-10 ounces shortly after you finish.

It’s important to note that if you are sweating excessively due to heat or humidity levels, you will need more fluid intake than normal in order to maintain your performance levels.

Avoid sugary drinks or energy beverages before or during exercise, as they can cause dehydration. If possible, opt for low-calorie alternatives such as coconut water, which contains potassium and magnesium. Consuming electrolytes like these will help replace minerals lost through sweat.

Post workout shakes can also help restore muscle glycogen levels. Opt for a low-carb, low-fat shake containing 20g of protein and simple carbs like good old agave nectar or honey.

Eat a Snack Pre-Workout

Snacking before a workout can help provide your body with the fuel it needs for an optimal exercise experience. An ideal snack should consist of protein and extra carbohydrates that can give you energy but also be easy to digest.

I usually go for a piece of fruit, such as an apple or banana, combined with a protein source like yogurt or nuts. Not only does the combination of carbs and protein give you sustained energy, but the fiber in the fruit helps keep you feeling full longer.

This type of snack is high in important nutrients, low in calories, and provides satiety without slowing down digestion too much. Eating this snack about 30 minutes before your workout will give your body time to digest it so that you have enough energy for exercise.

The combination of healthy carbs and protein will also help replenish glycogen stores that are used up during exercise and promote muscle growth and repair after your workout is complete.

Warm Up Before Working Out

Warming up involves doing gentle exercises to prepare the body for a more demanding workout. You shouldn’t skip the warmup because it prepares your heart and lungs for the intensity of the exercise you’re about to do.

When your body temperature increases, your blood flow increases, and so do your muscles as they use more energy. Warm muscles allow for more flexibility during movement, lowering your risk of injury when you start pushing those muscle fibers to their limits.

I suggest warming up with a series of dynamic (not static) stretches for at least 10 minutes before going onto the main event.

Limit Stimulant Intake

Trust me, I know how much cutting back on coffee sucks. I used to drink a silo of coffee every day, but not only was it negatively affecting my workouts, but I was also experiencing extreme bouts of anxiety.

If you don’t want to give up coffee altogether, keep your daily consumption below 400 mg (which is about four cups or two large mug-fulls). But caffeine-sensitive folks should abstain from it altogether.

Just a word of caution: do NOT quit coffee cold turkey! If you decide to stop drinking coffee altogether, taper off very slowly over the course of a couple of weeks. Caffeine withdrawal is a beast, which I learned the hard way.

Conclusion – Shaky Muscles Are Usually Nothing to Be Concerned About

If your muscles shake during challenging workouts, it’s usually no big deal – in fact, it is a sign that you are pushing your body, which can improve your overall fitness level.

However, occasionally shaking during exercise can be a sign of something more serious, so it’s important to pay attention to your symptoms, especially if you experience persistent shaking hours post workout.

Staying hydrated, eating a balanced snack before working out, warming up properly, and limiting stimulant intake are all key steps in keeping your workouts beneficial and injury-free.


Is it normal to shake during a workout?

Yes, it is normal to experience mild shaking mid-workout. Your body shakes when you push it to its limits. However, if the shaking persists or is accompanied by other symptoms such as dizziness or shortness of breath, stop exercising immediately and contact your doctor.

How do I stop shaking when working out?

Make sure you are properly hydrated, have eaten a balanced snack before working out, and have warmed up properly. Additionally, try to limit your intake of stimulants like caffeine as they can cause increased shaking. Aside from that, ease into your workout program gradually so that you don’t overdo it!

Is it better to work out with a full stomach?

No, I don’t recommend working out with a full stomach. Eating a balanced snack 30 minutes before working out is ideal as this will give your body time to digest the food and provide you with sustained energy without slowing down digestion.

What kind of snack should I eat before exercising?

Eating a balanced snack like a piece of fruit, yogurt, or a handful of nuts about 30 minutes before your workout is an effective way to keep energy levels up.

Corrie Alexander is a former ISSA-certified personal trainer, home fitness advocate, and founder of The Fit Careerist. A proponent of personal growth and a self-proclaimed fitness app-junkie, Corrie shares tips and product reviews with the goal of helping others on their own fitness journey.

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