CAN EXERCISE SUPPRESS OR BOOST THE IMMUNE SYSTEM?

written by: Nem​
Exercise can have a profound effect on your immune system. Depending on what kind of exercise you are doing, exercise can:

• Suppress the immune system
• Make it more robust or
• It may have no effect at all

​In order to maximize the beneficial effects of exercise on the immune system, you need to understand that all exercises are not created equal. Different types of physical activity will affect your immune response in different ways. Going for a 30-minute walk, running a marathon, and strength training will all have different effects on your immune system.

So, what makes these activities different?

There are two main exercise characteristics that you should pay attention to:

1. Intensity (e.g. jogging vs sprinting; 20 lbs weight vs 40 lbs weight; 50% your maximal heart rate vs 80% your maximal heart rate);
2. Volume (e.g. running 5km vs 42km; 10 repetitions with a 25 lb dumbbell vs 20 reps with a 25 lb dumbbell).

​It turns out that (like with almost everything in life) moderation is key. In order to have the strongest and most robust immune system you can possibly have, you should perform exercise at moderate intensities with moderate volume. Any kind of extreme and you start to weaken your immune system. 

​For example, if you've only been running 10km and then you decide to run 40km, you may suppress your immune system due to the dramatic increase in running volume and intensity.

If you've been lifting weights 2x/week at 2 sets/muscle group/workout then going into 4x/week at 4 sets/muscle group/workout, that extra volume might cause an immuno-suppressing effect.

Research is still not clear whether one bout of intense exercise can significantly decrease immune function. However, we know that perfoming exercise that's too stressful on our bodies with enough frequency can negatively affect the immune system. This is especially true if you have low glycogen stores, inadequate nutrition, poor sleep and a stressful lifestyle. 

You should still be introducing volume and intensity to your workouts regularly however, do so slowly. This gives your body an opportunity to adapt to the greater level of stress over time so you reduces chances of overloading your immune system. 

Someone might look at the previous paragraph and think "I'm just going to stay where I am now and not risk compromising my immune system by adding more exercise". You should only do this if you suspect you might be overtraining and have trouble recovering. 

However, a majority of people would benefit from adding more exercise. This is especially true if you find activities of daily living challenging since these very same activities can have an immuno-suppressing effect.

For example, let's say you are really out of shape and whenever you leave your house you need to take a flight of stairs. If whenever you climb up these stairs you lose breath and need to stop multiple times until you reach the top, then this activity wouldn't be classified as moderate and can therefore temporarily suppress your immune system. 

​
​WHAT DOES MODERATE EXERCISE EVEN MEAN?

​Now that you know that moderate exercise can help you improve your immune system, the problem is defining this term and finding what is moderate to you. 

After all, running 5km might sound moderate to you, but someone with a chronic heart condition and limited running experience would probably classify this activity as high intensity/high volume. 

So, when looking at activities we need to take into account our training status and classify activities in relative terms instead of absolute terms. 

​FINDING YOUR MODERATE INTENSITY

​If you are doing cardio, you can determine your moderate intensity by:

1) Asking yourself “How tired do I feel on a scale from 1-10?”. Moderate intensity is considered to be between 3-6 on the rate of perceived exertion (RPE) scale. 

2) Reach 40-70% of your maximal predicted heart rate. You can estimate your maximal predicted heart rate by subtracting your age from 220. Then multiply your current heart rate by your desired intensity of exercise. This will show you what heart rate you should aim for (target heart rate) during exercise. For an example:
Mary age 40 would like to work at 65% of her predicted max heart rate. To calculate this we would use the following formulas:

step 1) 220 – Age = Predicted Max Heart Rate
step 2) Predicted Max Heart Rate x Target Intensity = Target Heart Rate

Mary’s predicted maximum heart rate is: 220 – 40 = 180 beats per minute. 
If she wants to exercise at 70% of her predicted max heart rate, she should try to reach a heart rate of: 180 beats per minute x 0.70 = 126 beats per minute. 

3) The most accurate method of determining your maximum heart rate is by performing a progressive running test until exhaustion. You should generally avoid doing this test yourself considering the high risk of injuries and health events. Ideally, you would be supervised by a kinesiologist or an exercise physiologist who would monitor your physiological parameters and give you feedback.

If you are doing strength training, moderate intensity can be classified as:

1) 50-75 % of your 1 repetition maximum (RM). RM refers to the heaviest weight you can lift for one repetition.
2) 5-7 point rating on a 10 point rate of perceived exertion scale.
3) 3-5 repetitions in reserve (RIR). RIR refers to reps in reserve and this basically means that whenever you do strength training, stop 3-5 repetitions short of technical failure. 

​FINDING YOUR MODERATE VOLUME

​Finding your moderate volume is a bit tricky unless you've been training consistently for at least 3-6 months. If you are new to exercise and wondering how much volume you should be doing, always start slow and you can gradually add more. You want to avoid getting excessively sore or potentially injuring yourself.

However, if you've been training for a while, you’ve probably already found your moderate volume unless you exhibit any of the following symptoms:

1) no motivation to exercise,
2) frequent infections,
3) chronic fatigue,
4) trouble gaining weight,
5) frequent injures and bone fractures,
6) menstrual irregularities.

If you have any of these symptoms, consult your physician and reduce your exercise volume by 50% for 1-2 weeks and then reassess. A kinesiologist can help you assess your fitness and develop a program that would be appropriate for your level of fitness. 

If you don’t have any of these symptoms and you are looking forward to adding more exercise volume without compromising your immune system, start increasing volume gradually. 

With running this might mean increasing your running mileage by 10%. If you are strength training, you can keep your sets and reps the same and only increase weight by 5-10 Ibs. You can read more about strength training progressions in our article "How and When to Progress Your Workouts". 

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