You finish a workout feeling pleased with yourself. But an hour later, your legs feel heavy, climbing the stairs seems impossible and all you want to do is sit down.
Author
- Athalie Redwood-Brown
Senior Lecturer in Performance Analysis of Sport, Nottingham Trent University
The feeling of being drained after a tough working is often described as "post-workout fatigue" . You might feel low on energy, while your muscles may feel heavy, weak or less able to perform .
While some tiredness after exercise is normal, how much you experience can depend on the type of workout you've done, how hard you've worked and how accustomed your body is to it. Fortunately, there are things you can do to help your body recover.
What is post-workout fatigue?
There are two sides to fatigue. The first is perceived fatigue, which is your own feeling of tiredness and effort . The second is performance fatigability, which refers to a measurable drop in what your body can do - such as a muscle being unable to produce as much force .
The two don't always match perfectly, which is why fatigue is now understood as a complicated process involving both the body and our perception of tiredness .
Fatigue is also different from delayed-onset muscle soreness (Doms) - the aching and stiffness that can develop after working out. Doms typically happens if we've done an unfamiliar exercise, or when it's been a while since we last exercised.
Doms is also particularly associated with eccentric exercise (when a muscle works while getting longer) - such as when lowering a dumbbell.
Why does post-workout fatigue happen?
There isn't one single cause. Different processes contribute depending on what exercise you've done , how hard you've worked and for how long .
Some of this fatigue may be caused by the changes that happen inside the muscles, for example.
In order for our muscles to move during an exercise, they rely on electrically-charged particles called ions which trigger muscle contractions. But exercise also causes changes to these ions, which can affect the muscle's ability to contract and produce force later in their workout. This may explain why people feel like their muscles are depleted and fatigued after a workout.
The nervous system plays a part, too. The brain and spinal cord send signals telling our muscles to contract. Strenuous exercise can temporarily reduce the nervous system's ability to fully activate the muscles, contributing to what is sometimes called central fatigue .
Fuel is another factor, particularly during longer or demanding exercise. Our muscles store carbohydrates from the foods we eat to use later for energy. But exercise reduces these stores , which can contribute to fatigue.
Sweating also causes us to lose water and electrolytes , such as sodium, which are important for keeping our muscles and nerves working normally. If enough fluid is lost without being replaced, dehydration can reduce performance and make physical activity feel harder .
Is it worse if you're new to exercise?
Beginners to exercise may experience more soreness and and muscle weakness because their bodies aren't accustomed to the activity. However, even experienced exercisers can experience it - particularly when they try something unfamiliar. For example, a regular runner who rarely lifts weights may feel very sore after their first challenging weights session.
Fortunately for us, the body adapts. Repeating similar exercises generally cause less muscle damage and soreness - something scientists call the repeated-bout effect . A 2023 review found less muscle soreness and better preservation of physical performance after a second bout of muscle-damaging exercise compared with the first.
So, post-workout fatigue isn't just a beginner's problem.
How can you recover?
Some of the most useful recovery strategies are also the simplest: food, fluids, sleep and time .
After a long or demanding workout, eating carbohydrates helps replace the energy stores our muscles have used.
Protein is also important. Protein provides amino acids, which the body needs to adapt and recover from the exercise we've just done. However, protein supplements certainly aren't an instant cure for tired or aching muscles - and research into their effects on soreness and immediate recovery has produced mixed results.
Replacing the fluid we've sweated out is also important. For most shorter workouts, water is enough. But if you've done a long run, an intense workout session or have sweated a lot (such as during hot weather), you may want to consume some electrolytes as well.
Sleep is important as it gives the body further opportunity to recover. Research in athletes suggests that increasing sleep , either by sleeping longer at night or taking naps, may benefit aspects of physical and mental performance.
There's also some evidence for alternate recovery techniques, including gentle exercise (such as a slow walk or yoga), massages and water immersion. A review of 99 studies found several of these techniques could reduce muscle soreness, with massage showing one of the strongest effects on people's feelings of fatigue.
Can you prevent it?
You can't. But if you want to reduce how bad your post-workout fatigue is, try to avoid suddenly doing much more than your body is prepared for.
Starting a new activity at a manageable level and gradually building up gives your body time to adapt .
Making sure you're well hydrated before workouts is also sensible - particularly for longer workouts or when exercising in hot conditions.
Eating enough to support your activity and allowing time to recover between demanding workouts helps as well.
Most importantly, feeling completely exhausted doesn't necessarily mean you've had a better workout. Some fatigue is expected, but it should generally be in proportion to the exercise you've done and improve with recovery.
If the amount of fatigue you experience after a workout seems disproportionate to the workout you've done, doesn't improve with recovery or comes with symptoms such as chest pain, fainting or unusual breathlessness, speak to a doctor.
Athalie Redwood-Brown does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
