We all know exercise is good for your health. It helps relieve stress, helps you get stronger, and improves heart health. These are just a few of many reasons why you should exercise consistently. But you might be surprised to hear that there's something else that regular exercise can help improve... Your immune system.
When it comes to having a healthy immune system, most people resort to looking for the best immune-boosting foods to help. Which is great because the foods you eat directly affect how your body functions, but so does your physical activity! Now before you get too excited, this doesn't necessarily mean you can outrun that pesky bug or common cold you get every year. Sadly, it's not that simple. Here's exactly how exercise affects your immune system, how much you should exercise, and the best type of exercise that fires up your body's defenses to help fight off illnesses!
Can exercise boost your immune system?
It's a stretch to say that working out can boost your immune system... But it does affect it in a positive way. Exercising for 30 minutes or more causes an immune response. Here's how it works...
Your body senses a physiological stressor when you do any type of workout that gets your heart rate up for a sustained amount of time. This causes the body to deploy certain types of white blood cells from different parts of your body to flood your bloodstream. Those cells are powerful immune cells (such as natural killer cells and T cells) that find pathogens, like viruses, and wipes them out. So essentially, exercise helps those cells come out and circulate at a higher rate than normal. But there's a catch! That immediate response from your immune system when you exercise eventually goes away. The immune cells start to decline in your bloodstream, and that boost to your immune system only lasts about three hours. On the upside, if you regularly exercise, you'll continue to experience those effects.
Although working out a few times a year won't necessarily boost your immune system, doing it regularly can make a positive impact! Exercising a few times a week on a regular basis will create that immune response we discussed, and as time goes on it all adds up and can provide your body with health benefits like decreasing inflammation and improve your immune system's surveillance activity overall! In fact, a study published in the British Journal of Sports Medicine found that participants that did aerobic exercise five or more days a week lowered the number of upper respiratory tract infections (aka the common cold) over a 12-week period by more than 40%! Another recent study published in the Journal of Sport and Health Science found that obesity and inactivity lower the function of the immune system, but this can be improved by living a healthy lifestyle, that includes eating nutritious foods and regular exercise. Doing so will help improve the immune system and can even reduce mortality rates from respiratory illnesses. 
Another benefit that has to do with the immune system, is that exercise helps decrease inflammation in the body. A study published in the Journal of the American Geriatrics Society found a link between people who exercise often and have higher fitness levels to decreased levels of inflammatory markers. This goes hand in hand with our immune system because when the body is in a state of inflammation, it puts the immune system in an inflamed state too, thus making it harder to fight off infections. 
As you can see healthy living, which is eating mostly nutrient-dense foods and exercising regularly, is more than just about weight loss. It's about overall health and making sure your body's defenses are in top shape to minimize the risk of illnesses.
How much exercise should you do to improve your immune system?
Although exercise has positive health benefits, doing too much can have a negative impact on your immune system. Overtraining can actually increase your risk of infection. But don't get too worried yet, this only happens if you push yourself too hard for a long period of time and go past the acute level of training. For example, marathon runners, athletes, people that train at high intensity for longer periods of time regularly. Intense exercise like that can cause stress on the body which can lead to lowered immune function. So if your focus is to be healthy overall and to have a strong immune system then high-intensity exercise for over an hour is not going to do you any favors.
So how much exercise should you be doing for a stronger immune system? Adam Jajtner, an assistant professor of exercise science and physiology at Kent State University says that regularly exercising at a moderate intensity will help decrease your risk for infection. He also states that doing excessive, intense, vigorous exercise will increase your risk of infection. There's no way of knowing how long and how hard you can push yourself before reaching that intense level of exercise because it depends on your fitness level and how well you're trained. 
What's the best type of exercise to strengthen immunity?
When it comes to training for better overall health, you want to keep your exercise at a moderate intensity coupled with a balanced diet. If you have certain fitness goals in mind like weight loss or muscle building it's important to find a balance in your training. Making sure it's intense enough you get results, but not to the point that you're overtraining. Only you can know how hard to push yourself.
The U.S. The Department of Health and Human Services recommends at least 150 minutes of moderate-intensity exercise or 75 minutes of vigorous physical activity each week, spread evenly throughout the week.  To be specific, various studies suggest aerobic exercise like walking, running, or cycling at a moderate level is best to gain the benefits of exercise and the immune system. David Nieman, a health professor at Appalachian State University, suggests for other forms of exercise aim to reach about 60% of your VO2max or about 70% of your max heart rates.
So what does that mean for high-intensity interval training (HIIT) and strength training? Well, studies have mixed results. Some say HIIT improves immune function, others say it lowers. Strength training has been shown to help the immune system, but there are not as many recent studies to back it up. This doesn't mean you should write off these types of exercises completely, studies do still show that it helps with immune function, and remember, it all depends on how well trained you are. Regularly strength training with a mix of cardio and HIIT workouts, and eating nutrient-dense foods aren't going to impact your health negatively or lower your body's defenses. If anything, it will help make you stronger, improve your health, decrease stress, and so much more!
At the end of the day, it really depends on what your goals are, your fitness level, and your general lifestyle. Moderate-intensity exercise and cardio seem to be the best way to make sure your immune system is functioning at optimal levels, but remember, it also depends on your lifestyle. The best way to ensure your immune system is in top shape is by getting enough rest, eating a healthy balanced diet, making sure you aim to reduce stress levels by practicing self-care, and regularly exercises over a long period of time. All of these things will help improve your body's defenses to be able to fight infectious diseases!
With the current pandemic, we can all use a stronger immune system. So don't forget to take care of yourself, mentally and physically, wash your hands regularly, and keep up your workouts, don't let coronavirus stop you from reaching your fitness goals 😉And in case you need home workout ideas, or just need a workout plan that will get you effective results, check out the Fit With Iulia app. The first workout of every goal is available for everyone to try for free - No subscription required!