I get tired after 5 minutes of exercise

Workouts are tiring. You may find some days are worse than others, depending on the type of exercise or its intensity.  If...

Workouts are tiring. You may find some days are worse than others, depending on the type of exercise or its intensity. 

If your energy levels start flagging after just 5 minutes, it’s worth looking more closely at why that’s happening. And not because it’s necessarily anything to worry about, but because it may have a simple fix.  


6 reasons you might be tired after 5 minutes of exercise 


Low Glucose Levels  

Exercise can make big demands on our muscles, and it’s the food we eat that provides the fuel to power them through our workouts. The body breaks carbohydrates down into sugars. One of these sugars is glucose, and it’s the body’s main source of energy. When glucose hits the bloodstream, it can be used immediately, but if the body doesn’t need it right away, it’s stored as glycogen in the muscles and liver for later.

According to the Persona nutrition website, on average, the body stores around 400 calories of glycogen in the liver and around 1600 in the muscles. To put this into a different perspective, The British Heart Foundation writes that the body can only store enough glycogen for around 90 minutes of exercise. It’s why you’ll see endurance athletes using sports gels or drinks to boost their glucose levels.

You may feel tired after 5 minutes of exercising because you’re not fuelling your body effectively and running on empty.

Building and replenishing glycogen stores is important, which is done by consuming carbs. Here’s where understanding the difference between simple and complex carbohydrates is key.  

Healthline writes that simple carbohydrates are sugars. You’ll find them in sweets and candies, sugary drinks, many packaged baked goods and breakfast cereals, etc. General advice is to avoid consuming too many simple carbohydrates, but they are still a key component in fuelling the body. Live Strong writes that simple carbs are better for energy when consumed either immediately before or during intense or long-duration exercise.  

Complex carbohydrates are generally considered the better choice the rest of the time and are found in whole grains and high-fibre fruits and vegetables. Complex carbs take longer to digest, so they’re often stored as glycogen. If you don’t have enough glycogen stored, then you’re going to feel tired more quickly. Live Strong documents one 2015 study which found low muscle glycogen levels lead to ‘fatigue and may reduce the athlete’s ability to train and compete.’ If you’re on a carb-restricted diet, then it’s worth looking at whether you’re sufficiently fuelling your body well enough to cope with intense physical activity.

Be aware, too, that high-intensity exercise burns through glycogen stores more quickly, so even short periods of vigorous activity can deplete your body’s main source of energy. Long-distance running or cycling may burn through glycogen slower, but it will still have to be topped up past the 90-minute mark (or thereabout). Many diets demonise carbohydrates, but it’s important to remember that it fuels your workouts, so check that you’re eating the right balance of foods to support a more physical lifestyle.  

woman leaning chin on the railing tired

Trying too hard too soon

When you first start a fitness regime, it can be tempting to exercise hard and often. In the beginning, motivation is often at its highest, and there’s nothing like those first few sessions to get you pumped for more. Unfortunately, it’s easy to go too hard in the beginning and pay the price, especially if you’re new to exercising or if you’re recovering from illness or injury. Running is a good example of this.

Most people will start running as far as they can in one go and then stop, exhausting themselves but doing the same thing a few days later. Or they’ll jump straight into running for 10 or 30 minutes without any previous experience. This works for some people. It might not work for you. If you’re starting out and finding it difficult to manage 5 minutes, drop back on the intensity or add walking breaks. Reduce the resistance on your indoor cycling bike or adjust the incline on your treadmill. Don’t be afraid to slow down or take breaks. This isn’t just to help a physical response but a psychological one too. When you're struggling, it’s easy for the brain to want to stop before the body does. You may interpret it as tiredness, but it could be your mind just focusing on how difficult it is to exercise at that moment. It happens to a lot of people. Your brain is screaming at you to quit, so you do, and you feel relieved. Fitness is something that’s built, and it’s a process, so don’t worry about starting slowly or taking things right back to basics. You may feel tired in the beginning, but you will build stamina.  


Overtraining happens when a person fails to build enough rest days into a training plan. Feeling tired is one of the most common symptoms. Rest and recovery are key components of any exercise regime because it’s during these periods that your muscles repair themselves and become stronger. You may feel as if you’re resting and nothing is happening, but it’s a vital component in building fitness and strength.  

Without rest days, the ‘micro-tears in your muscles’ can’t heal, and so your muscles will ‘feel inflamed, swollen and exhausted.’  


Dehydration can have a significant impact on performance. According to Bannerhealth, a 2% reduction in fluids can lead to a 10 to 20% drop in performance. It can also prevent your body from thermoregulating effectively, making you feel more tired and sweaty. Men’s Health recommends 8 oz (237 ml) of water right before exercising and then doubling it within half an hour of finishing to ensure you’re hydrated. 

woman in gray tank top waking up in bed

Poor sleep quality 

Sleep doesn’t just help us feel better, it can also help us perform better. If you’re struggling with low energy while exercising, it’s worth tracking your sleeping habits. Much like the issue of overtraining, poor sleep prevents the body from repairing the muscles activated during exercise, and at night the body releases its growth hormone. Sleep is also an important factor in mental fatigue. You’re less likely to exercise when you’re tired, and even if you do, you’ll probably be more tempted to give up earlier. 

Potential underlying health conditions 

If you’re struggling with exercise and regularly feeling tired after only a few minutes, it’s worth talking to a health professional to see if there’s an underlying medical cause. Most people have the odd day where they just can’t muster the energy, but if it’s becoming more regular or if you’re worried, then it’s time to ask for a professional opinion. It could be as simple as a vitamin or mineral deficiency, or it could be related to a potential heart issue.

There can be several reasons for feeling tired after only a short period of exercise. It’s worth looking at what you’re eating and ensuring that you support any physical activity with a nutritionally balanced diet. Tracking your water intake and keeping an eye on the hours you sleep can also help. Overtraining can be detrimental to your fitness goals, so you should stay mindful of that, and don’t forget that your body is still benefiting from your workouts even when you take the night off. And, of course, if your tiredness persists or if you’re worried, then get a professional medical opinion.    

I'm always tired after work

Juggling a career with a fitness plan can be challenging, especially if you add in other personal and social responsibilities like raising children, caring for older family members, and being a valuable member of society, etc. 

Work can be draining. It's no wonder than many people prefer relaxing in the evening rather than hitting the gym, joining that team game or jumping on a bike. If you're always tired after work, then it's hard to stay motivated. 

There are several reasons why you may be struggling with energy levels, especially later in the day. If you're too tired to exercise after work then it could be due to: 

1. Poor sleep quality

2. Poor or unbalanced diet including vitamin deficiencies 

3. Dehydration

4. Stress

5. Chronic health conditions 

6. You have a physically demanding job

7. You have a mentally taxing job

8. You're overworked and burning out

9. You may have depression or low-mood

10. You're making poor snack or lunch choices

11. You find your colleagues exhausting

12. You just don't feel like going


It's not unusual to feel tired if you've been working during the day, but if you're feeling too tired to do anything else, then it may be a sign of something that needs addressing. This is when it's useful to keep a record of how you're sleeping, what you're eating, and how you're feeling, to see if any patterns emerge. Vitamin B12 or iron deficiency can cause fatigue. Depression can make us feel uninspired and apathetic even towards activities we used to enjoy. 

If you're concerned about how tired you're feeling after work, then make an appointment with a health professional. 

But if tiredness after working is just a reason not to exercise, then there are a few things you could try. 

1. Could you switch your exercise session to first thing in the morning? That gets exercise out of the way earlier and lets you crack on with your day. Some people exercise in their lunchbreak. This has a two-fold benefit because exercise not only makes you more productive but can also help you beat the post-lunch slump. 

2. Look at what you're eating throughout the day to decide if you can improve your diet in a way that supports energy release more consistantly. Try to look if the snacks your eating in the afternoon are causing a sugar spike that leave you feeling tired. Plan your meals and snacks so you have something with you before you exercise. You may also want to look into pre-workouts and supplements to support your exercise habit. 

3. Most of us recognise how a good workout leaves us feeling energised and in good spirits, but it's hard to remember that when we're fighting the urge to skip it. In the book Atomic Habits, James Clear recommends setting a goal that's as simple as putting your gym kit on and stepping outside. You're far less likely to skip it if you've put your clothes on and tied your laces. You can then decide just to go for 5 minutes. What you'll often find is that once you've started, you'll keep going. Like most things in like, the real challenge is starting. 

4. Exercising before you go home may also help. Change into your gym kit and work and go straight there or complete a run or studio session right after finishing. Equally, if you're exercising at a gym or class, then look at what's available near your workplace. Eliminating the commute home straight after work should help. Maybe see if anyone else would go with you and use them to hold you accountable. 

5. Get your gym bag, running, cycling, or class kit, accessories and equipment ready the night before. This makes it easier to just go rather than faffing about looking for what you need. 

6. Can you switch up when and how you're exercising? Could you cycle into work to get your cardio in? Could you walk from the station instead of hailing a taxi or calling an Uber. 

Exercise can be difficult if you're always tired after work, but we hope we've given you some ideas to help combat feelings of fatigue. On some days, it's better to listen to your body and take a rest, because being too tired to exercise after work may be a sign that you need to slow down and recover. 


Looking to supercharge your at-home exercise practice? Pre-order the electricity-generating RE:GEN today. 

Man in leggings and shorts sitting on a RE:GEN bike in a green lit studio

Back to blog

Leave a comment

Please note, comments need to be approved before they are published.


Solutions for every setting