Should You Exercise When You’re Tired or Sleep-Deprived?

Should you exercise when you're tired or sleep-deprived?Once you’re committing to staying fit, you don’t want anything come between you and your workout. Even when you’re on a tight schedule, you find a way to fit in an exercise session. Fortunately, when you’re exercising at home, that’s not so hard to do.

Commitment to fitness is a good thing as long you keep the bigger picture in mind – your health. Some people become so committed to their workout that they exercise when they’re sick or exhausted after a night of too little sleep. To be fit AND healthy, it’s important to strike a balance. That means making rest a part of the equation – and know when rest is the best option. Here’s the question. If you’re exhausted from lack of sleep – should you work out when you’re tired and sleep-deprived? Find out why rest is the best option.

 Your Performance Will Be Sub-Par

Even one night of little sleep can affect your workout. A study published in the International Journal of Occupational Medicine and Environmental Health showed that reaction times decrease and performance on tasks like driving and operating machinery declines. Cognitive function suffers too. It becomes harder to make decisions and memory is impaired. Plus, sleeplessness increases sensitivity to pain. That means your workout will feel all the harder even when you aren’t working as hard as usual.

Another study showed that one night without sleep decreased performance during endurance exercise and participants had a higher perceived level of exertion. In other words, even though they ran a shorter distance than usual, it felt harder.

The take-home message? If you work out when you’re sleep-deprived or very tired, it’s unlikely to be a productive session.

Your Risk for Injury Goes Up

With your reaction time slower and thinking skills and judgment clouded by fatigue, your risk for injury goes up when you’re tired or sleep-deprived. Why risk an injury just to say you worked out? Better to rest and approach your workout with fresh enthusiasm because you’re rested and operating at peak efficiency.

It Negatively Impacts Your Immune System

It doesn’t take much sleep deprivation to cause problems. Even one night of poor or inadequate sleep raises cortisol levels. This puts a damper on your ability to fight off infection. Combine that with the added stress of a hard workout and you put yourself at greater risk for whatever virus happens to be making its rounds. When you’re exhausted, you need rest to lower your cortisol levels and get your immune system back up to snuff.

The Effects of Inadequate Sleep Are Cumulative

If the time you’re using to work out in an exhausted state cuts into your sleep time the next night, you’ll feel even less “perky” the next day. After being sleep-deprived for a few nights, your performance, cognitive function and reaction time declines even more. That means you could end up having several days of less productive workouts and be more likely to injure yourself.

It Interferes with Tissue Repair

When cortisol levels are high, it interferes with tissue repair and growth. In addition, anabolic growth hormone is released primarily during the deeper stages of sleep. When you’re sleep-deprived, it creates an unfavorable metabolic environment for growth and repair. Better to rest and get a good night’s sleep than further stress your system with a workout. This will only raise your cortisol levels further.

Other Reasons Sleep is Important

Sleep doesn’t just impact your workout and ability to build muscle, sleeping less than 7 hours a night has been linked with a greater risk for health problems like type 2 diabetes, heart disease, hypertension, an increased risk for weight gain and higher mortality. Plus, it has a negative impact on mood. Who doesn’t feel grouchy and a little anxious when they haven’t slept?

The Bottom Line?

When you’re exhausted and slept very little the night before, take a rest day and let your body recover and stress hormones normalize. If you work out in an exhausted state, your workout won’t be as productive, tissue repair will be compromised and you’ll increase your risk for illness due to decreased immunity. Plus, you probably won’t work have a very productive workout. Maximize your nutrition and give yourself a day to rest and recover. It won’t negatively impact your fitness level. It’ll help you be fitter and healthier in the long run.



Int. J. Occup. Med. Environ. Health. 2010: 23 (1): 95-114.

Eur. J. Appl. Physiol. 2009 Sep: 107(2): 155-61.

Washington State University. “How sleep affects sports performance”

Medscape.com. “Insufficient Sleep Thwarts Weight Loss Efforts”

Sleep. 2010 May 1; 33(5): 585–592.

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