Does exercise boost your immunity? Intensity matters!

Flu-phobia is spreading faster than the virus itself lately. Personally, I’ve used more hand sanitizer this week alone than I’ve used in my entire life! But even if you make it thru the H1N1 outbreak this season, you’re still likely to get bit by at least one bug this year. Actually, the average adult catches two to three upper respiratory infections each year. Not too bad, considering we’re constantly being exposed to viruses day in and day out. But some people are more susceptible than others to catching whatever is going around.

Here’s a few things that increase your chances of catching colds or flus:
-Poor nutiition
-lack of sleep
-over training

So what can you do to give your immune system and extra boost? Research has been showing a connection between moderate, regular exercise and a strong immune system. Exercising at a moderate intensity level (approximately 70 – 75% of your VO2 Max), has been shown to have a positive response on the immune system and temporarily increases the production of cells that attack bacteria. Researchers believe that consistent exercise can have big immunity benefits over time. This makes sense because when you’re exercising at a moderate intensity, immune cells circulate thru your body faster so they’re able to kill more bacteria and viruses. The more often you exercise, the more benefit you may get over the long run. The effect seems to be cumulative according to at least one researcher.

However, there is a point where you cross the line. Too much intense exercise can lower your immunity! Research shows that exercising at a high intensity for over 90 minutes can make you more susceptible to getting sick for up to 3 days after your workout – yikes! During high intensity bouts, the body produces stress hormones (cortisol and adrenaline) which raise blood pressure and cholesterol levels while weakening your immune system. That’s why it’s important to get proper rest and recovery time after endurance events and long, hard-core workouts. Over training will surely weaken your immune system. The symptoms of over training are increased resting heart rate, a slower recovery heart rate, fatigue, irritability and a feeling of heaviness or lethargy.

If you’ve already come down with a virus or infection, it’s okay to exercise at a light or moderate intensity because it will boost your immune system and will likely make you feel better. But intense activity will make it worse and probably even extend your illness. When you’re sick, your body is working hard to fight whatever you caught – stressing it more is like adding insult to injury!

Jill Brown
Jill Brown
Hi, I'm JillI am a Los Angeles based Fitness + Nutrition Coach. With 20+ years of experience in teaching, training and continuing my education, I have transformed thousands of lives through fitness and healthy lifestyle changes.