Skip to main content

Post Workout Fatigue – Why It Happens And How To Help


Exercise is meant to make you feel good, and can even help to boost your energy, so if you constantly find yourself feeling fatigued after your workouts, it’s a sign that something isn’t right.

If you struggle with extreme fatigue after workouts, we’re here to help. In this article, we look at why some people feel so tired after workouts, how to combat post-workout fatigue, and how to prevent it.

What causes post-workout fatigue?

Before we dive into the causes of post-workout fatigue, let’s look at the different ways it might be experienced:

Extreme fatigue or lethargy shortly after a workout

Do you feel fine before your workout, but really tired after the workout? There are a few elements that could be at play here, including:

  • Dehydration

    Fatigue is one of the most common symptoms of dehydration, and exercising increases the water we lose through sweating and breathing.

    How to fix it:

    Make sure you drink plenty of water before, during, and after exercising (as well as regularly throughout the day). You can also opt for sports water as this helps to replace electrolytes lost through sweat and can improve hydration levels quickly.

  • Low blood sugar

    Exercise uses up the glucose in our blood, and the glucose stored in our muscles (known as glycogen). If you’re exercising at a moderate to high intensity, you can actually use up all of the body’s reserved glucose, which causes low blood sugar.

    How to fix it:

    Make sure you are properly fuelling up before your workout by eating a meal or snack that has plenty of carbs, and eat some carbohydrates shortly after your workout to replenish your glycogen stores. We’ve shared energy-boosting food ideas to fuel your workouts here.

  • Training intensity

    Are you a big fan of HIIT, or other high intensity training styles? High intensity exercise uses anaerobic energy pathways to produce energy. While this is great for producing short bursts of power and intensity, it creates an oxygen deficit and produces lactic acid, both which the body has to restore after exercise. This in itself consumes energy, and also means there’s less oxygen (as well as glycogen), which can also impact energy levels.

    How to fix it:

    Keep HIIT sessions short, and cut back on how many you do. Although it can be tempting to do every workout as HIIT, you should only be doing 1-2 a week.

Fatigue the day after a workout

If you struggle with post-workout fatigue the next day, or constant low energy levels following workouts, there’s a lot of lifestyle factors that might be causing this.

  • You’re doing too much

    Are you guilty of skipping rest days in favour of daily workouts? Taking time each week away from the gym is crucial to giving your body enough time to recover and repair the muscles and joints. Exercise is actually a stressor on your body too, so constantly exercising without time to rest can lead to symptoms of chronic stress – including fatigue.

    You might be having rest days but cramming too much into your workouts. Pushing yourself too hard won’t help you progress faster. If anything, it will cause fatigue, and possible injuries. 

    How to fix it:

    Make sure you are taking at least one rest day a week, and aim to leave at least 48 hours between working the same muscle group twice – no doing 5 full body workouts a week!

  • You’re not eating properly

    You’ve heard the term food is fuel, and the saying is true. Not only do you need to eat enough calories (find out why eating too little is bad here), you need to make sure you are getting enough carbs, proteins, and fats for the exercise you are doing. Simply being alive uses energy, so eating too little means there’s not enough energy left for working out. 

    Carbohydrates help to ensure there is energy readily available for your body to use, while protein is essential in repairing tissue in the body (like muscle). Fats help the body to absorb vitamins and support cell growth.

    How to fix it:

    Making sure you eat eating enough food and get a good balance of all three macros will provide your body with enough energy for your workouts and to recover properly, so you don’t feel tired the day after your workout.

  • You’re not getting enough sleep

    A bad night’s sleep goes hand in hand with feeling tired, but even more so when you add exercise into the mix. Getting enough sleep allows the body to rest and repair, including our muscles and heart. When we are deprived of sleep, it takes our bodies longer to recover from workouts, which leaves us feeling fatigued.

    How to fix it:

    Work on getting at least 6-8 hours’ sleep every night. Try keeping consistent sleep and wake times, avoiding bright screens before bed, and practicing meditation or mindfulness before bed.

  • You’re stressed

    We all get stressed now and then, but if you’re chronically stressed or feeling anxious, it can have a huge impact on your wellbeing and energy levels. While exercise is great for your health, it’s a stressor on the body. For healthy individuals, this is no reason to be alarmed, but if you’re already dealing with prolonged stress, it can make symptoms like fatigue worse.

    How to fix it:

    Work on lowering your stress levels. This sounds easier said than done, but there are plenty of ways to help manage stress, including practising mindfulness, building resilience, and talking to people.

Exercise is great for our health, but it needs to be part of a healthy lifestyle if we want to reap the benefits. Make sure you get enough sleep, are eating a healthy balanced diet, and looking after your mental health, as well as exercising, will lead to improved energy levels.

Working with a Personal Trainer can help to achieve a more holistic approach to your health, as they’ll be able to identify areas where you may need improvement.

All blog posts