June 1, 2020

Sleepiness and Fatigue Post-Workout: Good or Bad?

Photo: Unsplash/Vladislav Muslakov

Worn Out After Your Workout?

Regular physical activity helps boost your energy levels by increasing your heart rate and blood flow which in turns helps you to feel more awake. So since this is the case, you’re probably wondering how you could possibly feel sleepy after your workout. Well, it is common to feel some fatigue post-workout, especially after a high-intensity sweat sesh where you are expending a lot of energy; however, there are many other factors that may contribute to sleepiness after a daily workout. The fatigue you experience post workout could be a sign that you are not treating your body as well as you should. 

What’s Up With the Post Workout Sleepiness?

Your energy level after exercise depends on many factors including your current fitness level, the type, duration and intensity of exercise, your diet, your level of hydration, and how much sleep you obtained the night before. Post-workout sleepiness is the body’s natural reaction to physical activity. Muscle contractions are produced using adenosine triphosphate (ATP), a molecule that provides energy to the cells. During exercise your muscles contract, depleting energy stores. Decreased levels of ATP result in a reduction in your muscle’s ability to function leading to muscle fatigue. When your routine is too strenuous, the demand for ATP is higher, and it can leave your energy reserves depleted (2). That’s why you may feel extreme fatigue after an especially grueling training session.

Feeling a bit tired is normal and that fatigue is your body’s way of telling you it needs rest and nutrients to rebuild your muscles and reenergize so you are ready for your next workout.

Brain Drain

The neurotransmitters dopamine, norepinephrine, and serotonin are released in response to exercise which help regulate mood. Increased levels of serotonin boosts your mood and overall sense of well-being (1). A flood of dopamine into the brain creates feelings of pleasure and reward, which motivates you to repeat a specific behavior. Norepinephrine produced through exercise also helps to improve alertness and energy. 

However, the increased release of neurotransmitters can actually reduce your central nervous system’s (CNS) capacity to activate muscles during exercise leading to central fatigue (2). During physical activity, the CNS repetitively fires signals to activate your muscles during your workouts. This repetitive firing can become less charged the longer you workout. Both of these things can leave you tired and ready to take a nap. 

Beat Post-Workout Fatigue with Proper Nutrition & Adequate Sleep

Although the intensity of your workout may be triggering fatigue, the cause may lie in your routine before your workout. Post-workout fatigue can be caused by dehydration, lack of sleep or undernourishment, which together hinder muscle recovery. Experts at Harvard’s Healthy Sleep website and the National Sleep Foundation believe that ignoring one of the three pillars of health – diet, exercise and sleep – could cause the other two to suffer.

Significant differences can be seen in the mood, concentration and mental skills of those hydrated versus those in a mildly dehydrated state. Research shows that dehydration causes headache symptoms, loss of focus, fatigue and low mood at rest and during exercise (3). Multiple studies confirmed that an increase in tiredness and a decline in alertness and concentration was associated with a mean dehydration level of 2.6% body mass loss. It is also interesting to note that a wide variety of mood states such as vigor, perception of task difficulty and fatigue are affected at a dehydration level of 1.36% body mass loss which can occur very quickly if you are not properly hydrating before and during exercise (3). 

Sufficient sleep is critical to our overall health and sleep deprivation can have a negative effect on athletic performance. There are proven negative effects of sleep deprivation including impaired reaction time, reduced accuracy, decreased vigor, submaximal strength and decreased endurance (4). Some of your cognitive functions may also be affected such as judgement or decision-making. Most adults need about 7-9 hours of sleep per night and studies show that negative effects are seen with just 2-4 hours less sleep per night. Some experts find that those who are sleep deprived may not only experience poor performance during peak exercise but also crave unhealthy foods that promote weight gain (4). 

Food is the fuel that is broken down into energy that you require for exercise. If you are fueling your body that lacks nutrient density, you are depriving your body of the nutrients it needs to perform optimally. So, you will not only want to make sure you’re staying hydrated, but also fueling your body throughout the day with nutrient dense foods such as non-starchy vegetables, clean proteins, complex carbohydrates and healthy fats. And of course, we all know sleep is SO important. 

What’s the Takeaway?

It is always important to listen to your body. After a strenuous workout, you are physically stressing your body and will need to replenish with water, nutrients and rest to recover. Feeling a bit tired is normal and that fatigue is your body’s way of telling you it needs rest and nutrients to rebuild your muscles and reenergize so you are ready for your next workout. However, if you are having to get right back into bed post-workout, you are most likely sleep deprived, or not taking care of your body as well as you could. This level of fatigue may also be because you are engaging in an activity that is too strenuous for your fitness level. In rare cases, fatigue or exhaustion may be the result of a medical condition. If you have any medical symptoms in addition to your exhaustion after exercising, contact your doctor. 

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