Fatigue is a funny thing. Even though your body feels too tired to move, sometimes a workout is just what you need to vanquish lethargy. In fact, a study carried out by researchers at the University of Georgia found that engaging in regular, low-intensity exercise can boost your energy level by up to 65%. However, there are times when sleep and relaxation are more important than launching into a workout, especially a high-intensity one. When should you work out and when should you sleep or rest instead? It’s important to distinguish between physical fatigue and mental fatigue and lack of motivation.
Sleep or Exercise?
You might feel like it’s a cop-out not to work out when you have an exercise session planned. However, there are times it’s better to rest than work out. If you fell short on sleep the night before, a nap will serve you better than a workout. Exercise, although it might boost your energy level short-term, won’t make up for lost sleep and accumulated fatigue.
One criterion to use when deciding whether to exercise is whether you have a sleep deficit. If you tossed and turned half the night or only got four or five hours of sleep, getting a quality snooze should be the top priority. Likewise, if you only got six hours of sleep a few nights in a row, your body has accumulated fatigue that can only be remedied with a good night’s sleep.
Why should sleep be a top priority? Being deprived of sleep can cause a rise in cortisol, a stress hormone. Combine it with a high-intensity workout or workout of long duration and it will further elevate your cortisol level. Why is this a problem?
Cortisol, when too high, has a variety of negative effects on your body, including suppressing your immune system and boosting muscle breakdown. That’s counterproductive to building muscle! Plus, when you don’t sleep enough, it interferes with muscle recovery. Most muscle repair occurs during the deep stages of sleep when you release the most growth hormone.
Working out in an overly fatigued state can have other consequences. If you exercise on a day you’re severely sleep-deprived, the additional surge in cortisol after your workout can make it hard to sleep afterward even if you’re deprived of sleep. If you feel like you need to exercise after a night of little sleep, keep your workout slow and gentle. A relaxing yoga workout might be a good choice. Save the high-intensity workouts for a day you’ve had plenty of sleep and give yourself adequate recovery between high-intensity sessions. Some people alternate high-intensity workouts with low-intensity ones to allow sufficient recovery and lower the risk of overreaching or overtraining.
Research also shows skimping on sleep hampers sports performance and that can apply to weight training too. When you’re tired, you’re less aware of your form when you train. It’s harder to focus on the details of training too, such as how you’re breathing and whether you’re maintaining good alignment. Studies also show that athletes who get inadequate sleep or have poor sleep quality may be at higher risk of injury.
Then, there’s the impact lack of sleep has on your immune system. When you’re sleep-deprived and your energy reserves are low, your body preserves energy by downgrading the activity of certain organs, including the immune system, that it deems less critical to survival. Studies show when people are sleep-deprived, they’re more likely to become ill when exposed to a virus.
Is It Fatigue or Lack of Motivation?
Being physiologically fatigued is different than being mentally fatigued and lacking motivation. If don’t feel motivated and have been working out regularly, you may need a day off to relax your mind. However, mental fatigue can also come from working too hard on your job or mental stress from other factors in your life. In this case, a workout may be just what you need to shift your focus away from mental stressors. There’s a reason some people call exercise “meditation in motion.” The rhythmic movements are a panacea for worry and just what your brain needs when you’re mentally tired and lack “get up and go.”
Often the best form of exercise when you need stress relief is exercise that works your large muscle groups in a rhythmic manner such as walking briskly, running, a spin class, or a step workout. However, some people find that strength training provides a release for mental stress. If your stress levels are unusually high, a yoga workout might be just the ticket to help you relax and unwind. Plus, some research shows that yoga may lower the stress hormone cortisol. Some studies show yoga relieves depression by reducing cortisol.
One caveat; some research shows mental fatigue can make physical exercise feel harder and that can cause you to fatigue earlier. So, listen to your body and do what feels right on a given day.
The Bottom Line
It’s important to distinguish between physical fatigue due to lack of sleep or poor sleep quality and mental fatigue due to mental stress. If it’s the former, make sleep your priority, but if it’s the latter, a workout could make you feel better. Listen to your body and know there are times when rest is better for you than a workout. After a good night’s sleep, you’ll come back stronger than ever! Also, don’t underestimate the importance of getting enough sleep for meeting your physical goals. Most adults need between seven and eight hours of sleep per night Make sure you’re not falling short.
References:
- Current Sports Medicine Reports: 11/12 2017 – Volume 16 – Issue 6 – p 413-418. doi: 10.1249/JSR.0000000000000418.
- Sports Med. 2015 Feb;45(2):161-86. doi: 10.1007/s40279-014-0260-0.
- org. “Exercise and stress: Get moving to manage stress”
- com. “Low-intensity Exercise Reduces Fatigue Symptoms By 65 Percent, Study Finds”
- University of Georgia. “Low-intensity Exercise Reduces Fatigue Symptoms By 65 Percent, Study Finds.” ScienceDaily. ScienceDaily, 2 March 2008.
- Anxiety and Depression Association of America. “Physical Activity Reduces Stress”
- org. “How to Have Productive Rest Days”
- Indian J Psychiatry. 2013 Jul; 55(Suppl 3): S405–S408. doi: 10.4103/0019-5545.116315.
- org. “Lack of sleep: Can it make you sick?”
- com. “Mental Fatigue Can Make Exercise Harder”
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