I get tired after 5 minutes of exercise

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 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.    


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