If you exercise regularly, you probably already know the catalogue of benefits fitness brings to your life. Moving your body frequently lowers stress, improves mood and mental health, boosts problem-solving and memory, regulates sleep, and pretty much makes you a nicer person to be around.
In addition, if you're a moderate exerciser, you may have noticed that you take fewer sick days than your coworkers. Or you might be the only one of your friends who doesn’t catch that cold going around. This isn’t just your imagination — numerous studies have demonstrated that regular exercise improves how well your immune system functions.
Our immune system is complicated: it works to fight off viruses, bacteria and other pathogens. It's like chemical and biological warfare inside the body. When the system works well, we're able to battle invaders and stay healthy. When the system is overwhelmed or ineffective, we get sick.
A fascinating paradox in human physiology is the concept of a J-shaped relationship between exercise training and health. The “J-curve” suggests that, in general, people who exercise regularly at a moderate intensity experience fewer illnesses and infections than those who don't exercise. The relationship is based on research that measured the number of upper respiratory tract infections, such as the common cold, that people experience every year.
But here’s a finding that might surprise you: increasing the amount of exercise beyond moderate levels doesn't improve immunity further.
Quite the opposite, in fact.
When athletes train at volumes and intensities excessively higher than normal for extended periods, they experience a significant increase in the number of respiratory infections. Introducing a high volume of hardcore exercise is stressful on the body. The immune system is compromised and it's easier to fall ill.
So the takeaway here is that regular, moderate intensity exercise keeps your immune system strong and reduces the number of viral or bacterial infections that will lay you low. And as a person who already exercises more than five days a week at a low to moderate intensity, if you do get sick, you can expect milder symptoms and about half the number of sick days than your inactive counterparts.
But what about using exercise to heal yourself if you do become sick? Is it even possible?
The answer is yes and no. In some cases, you can help yourself heal. In others, you’ll just make things worse. To figure out the difference, let’s start with the “no” side of the equation:
If you pick up one of those brutal bugs with symptoms like muscle and joint pain, fever, diarrhea and vomiting, no activity is going to help you out and just about any could even be dangerous.
This isn't a time to stick to your fitness routine out of fear that you’ll lose your conditioning or out of hope that you’ll fight your way back sooner from the fever. This is a pure rest and recover situation. Your body is already under tremendous stress, and you have to keep a close eye on your symptoms in case they worsen.
Here’s the “yes” side of the equation: if you’ve got the basic sore throat, coughing and runny nose trio, low to moderate intensity exercise will actually help you to heal. So long as you’re not in the fever zone, activity such as light resistance training, yoga, walking, tai-chi, gardening or a slow-paced run will not only lessen the severity of your symptoms but also speed your recovery.
Why does moderate activity help with those basic afflictions that sometimes come our way? Because exercise improves the flow of fluids in your lymphatic system, which means that viruses, bacteria and toxins are filtered from your blood and lymph more effectively. And your immune system gets a boost from the bodily movement and works to get you back to health.
So your first defense against getting sick is also your second defense if you find yourself under the weather: low to moderate intensity exercise. It really is your immune system’s best friend. You can help yourself to heal by moving your body.
Want to stack the deck even more against illness? In addition to your exercise routine, add these to your daily routine: 7.5 (or more) hours of sleep per night, nutrient-rich fresh foods, meditation and downtime with friends and family.