The Surprising Way Lack of Sleep Affects Workout Performance

The Surprising Way Lack of Sleep Affects Workout Performance

Here are a few things to consider before you pursue a PR after a poor night’s sleep.

By Suzanne Steinbaum, DOUpdated February 10, 2022


How’s your sleep? It’s a question I ask every one of my patients because as a cardiologist, I know how incredibly important rest is to heart health. You probably already know that missing out on sleep makes you more irritable and hungry the next day. But getting less rest than your body needs can also affect a key biomarker called heart rate variability (HRV), which correlates to how hard you can exercise during workouts and how quickly you’ll recover.

What Is Heart Rate Variability and How Does It Impact Your Fitness?

Heart rate variability measures the variations in time between each heartbeat. Let’s say, for example, that your resting heart rate is 60. That doesn’t mean your heart literally beats once every second. There are tiny variations in the timing of beats. We’ve all been trained to think that any heartbeat irregularity is bad, but in the case of HRV, having more variation in the timing is actually a sign of vitality.

HRV is controlled by your autonomic nervous system (ANS), the same system that regulates blood pressure, digestion and the fight-or-flight stress response. Your brain sends signals to your ANS based on all kinds of emotional and physical situations: Feeling elated after a great date or anxious after a stressful meeting; getting a solid night’s sleep or tossing and turning all night; enjoying a balanced meal or downing a caramel latte and lemon loaf at a coffee shop drive-thru because you left the house without breakfast and are starving.

Our nervous systems are built to handle these ups and downs. But if your body is in a constant state of stress from poor nutrition, bad sleep or emotional upheaval, your ANS gets “stuck” in fight-or-flight mode and, among other things, your HRV drops.

When HRV is high, there is a lot of variability between heartbeats and your cardiovascular system is flexible, resilient and ready to perform—whether that’s during a strength training session, an endurance run or a live class with Cody Rigsby (who makes me sweat and laugh simultaneously). High HRV means that the calm, relaxed part of your ANS, called the parasympathetic nervous system, is in charge.

When HRV is low, however, that means that the fight-or-flight (sympathetic) nervous system has the wheel, and your body and brain are under more stress. It also means that it might not be the best day to attempt a PR or catch that guy you’ve been chasing on the Leaderboard for months. Low HRV has been linked to poorer performance in athletes, and although research is ongoing, many professional teams and elite athletes are now using HRV to help adjust their training routines.

How to Measure Your HRV

By now, you’re probably pretty curious about your own HRV. Most of us don’t need to know the exact numbers, but if knowing them will help you make important lifestyle changes, there are a couple of different ways to get that information.

The way to get the most accurate HRV reading is by having your doctor analyze the results of a 24-hour monitor or an electrocardiogram, taken over time, in their office. But you can also get a decent estimate at home with a chest strap heart rate monitor and an app such as Elite HRV. Some wearables, like the Oura ring, also track heart rate and calculate HRV.

5 Ways to Improve Your HRV

There are several simple things you can do to increase your HRV, whether you know the exact numbers or not.

  1. Consider biofeedback training. If you and your doctor decide that improving HRV is an important health goal, you may want to look into biofeedback, a mind-body therapy that has been shown to improve mood, lower stress and increase HRV. With the help of sensors and a biofeedback practitioner, you train yourself to make adjustments to your breathing and other bodily functions over time.

  2. Do a “brain dump” before bed. Lying in bed and going over your checklist of to-dos and anxieties every night is a recipe for tossing and turning. So, whatever is on your mind, jot it down on your computer, your smartphone or a piece of paper and leave it outside your bedroom. This allows your mind to calm down a bit and symbolically lets you leave those stressors behind.

  3. Book a mental health check. Your mental and emotional health greatly impact HRV and your overall heart health. If you have symptoms of anxiety or depression, consider making an appointment with your doctor or a psychotherapist for a screening. Stress is one of the most obvious causes of sympathetic nervous system overdrive and a reduction in HRV.

  4. Schedule wind-down time at night. What do new parents do when they have little kids and it’s time to go to bed? They give the baby a nice bath, then read a book, give them a bottle or nurse and then put them to bed. There’s a reason pediatricians recommend bedtime routines like this to parents—because they work! And not just for children, but for adults too. If you have a hard time falling asleep, take a look at what you’re doing in the hour before you go to bed and try to create your own restful routine. A warm shower, a five-minute stretching session, a cup of herbal tea or sleep meditations are all great options.

  5. Step off the Peloton Bike or Peloton Tread for a rest day. In general, exercise protects your heart and increases HRV. But overtraining can lower HRV and have negative impacts on your overall mental and physical wellness. There’s a difference between pushing yourself and pushing yourself too hard. Rest and recovery are essential to get stronger, so don’t feel guilty: Take a day off. Your body will thank you for it.

Dr. Suzanne Steinbaum is a leader in preventive cardiology, now in private practice in New York, and is a paid consultant of the Peloton Health and Wellness Advisory Council. She is the CEO/Founder of Heart-Tech Health, a technology-based prevention model. She published Dr. Suzanne Steinbaum’s Heart Book: Every Woman’s Guide to a Heart Healthy Life, and has been a national spokesperson for Go Red through the American Heart Association for 18 years. Follow her on Instagram and Twitter.

The content [provided here] is for informational and educational purposes only and does not constitute individualized advice. It is not intended to replace professional medical evaluation, diagnosis, or treatment. Seek the advice of your physician for questions you may have regarding your health or a medical condition. If you are having a medical emergency, call your physician or 911 immediately.