Exercise & Your Immune System

Virus, Immune System, Health

We all have our own personal health & fitness goals.

The 'big wins' that most of us are interested in...

(and that motivate us to maintain the required energy and discipline)

Are usually one, or more, of the following;

  • reduce body fat/lose weight

  • build/maintain muscle

  • improve cardiovascular health/performance

  • improve strength

  • improve general health (reduce heart disease risk, help to prevent diabetes etc)...

What you may or may not be aware of...

While you are working towards your main goals...

Is the huge effect that exercise is probably having on your immune system...

Therefore directly affecting your overall health and risk of illness.

That effect, will be a positive effect in most cases.

But the effects of exercise can also go the other way...

...and potentially weaken your immune system.

So don't make the mistake of assuming that "more exercise"...

... equals a "stronger immune system"!

As with most physical health outcomes...

There is a 'goldilocks effect', where there is a "just right" amount/volume of exercise to produce the desired result.

A Complex System & The Myth Of 'Boosting' Immunity

Your immunity to disease and illness is determined by the ability of a complex system to defend against invading bacteria and viruses.

Even in a 'healthy' person, the status of many variables will cause the supposed strength of your immune system to fluctuate.

For example, you could have a perfectly healthy lifestyle, and as a result, fairly robust immunity to common illness.

But even just one night of poor sleep will lower those defences, and raise your risk of infection the next day.

So strictly speaking, the idea of a 'strong' or 'weak' immune system is not black and white.

Also, while there are certain lifestyle decisions that will affect the relative strength of your immune system, don't make the mistake of thinking that you can train your body to become immune to all illnesses...

That goes for nutrition (including supplements) as well as exercise and lifestyle.

So, while you can (and definitely do) influence your immunity with various choices that you make every day, there are also a number of factors which you have no control over. And these factors also have a big effect on your chances of becoming ill.

For example, Covid-19 is (at the time of writing) a 'novel virus'...

Your immune system has never encountered it before and therefore has no innate ability to defend you from the disease after the virus has entered your body.

This applies to everybody...

Regardless of how 'strong' your immune system is.

On the other hand, your immune system should be better equipped to deal with more familiar enemies such as the common cold.

In those cases, the relative strength (or weakness) of your immune system becomes more relevant.

And this is where the information in this article may prove most effective.

Regular exercise is one of those lifestyle factors that affects the immune system...

And that you do have control over.

Jogging outside
Being fit & healthy definitely helps to support your immunity... but it doesn't make you bulletproof!

The positive effects of exercise on your immune system can be achieved through;

  • moderate types of cardio exercise (walking, jogging, cycling etc)

  • strength/resistance training

  • high intensity cardio

  • yoga (& meditation)

Note: In healthy people, the immune system either works optimally (keeping you healthy), or it doesn't...

With many, different variables affecting just how well your system is working at any given time.

If it is currently functioning the way that it should do... you cannot technically 'boost' it further using special supplements or nutrients.

Remember, you can't be 100% immune to all illness.

So the question is not "which tricks or 'bio-hacks' can I use to further enhance my immune system..."

Instead ask yourself...

"Is my immune system working optimally. If it is, how do I maintain that...

...and if not, what can I improve in my diet or lifestyle, to achieve that optimum function?"

This is important to remember... Many companies/brands market products (such as food supplements), which claim to "boost" the immune system. This suggests that the product performs a function that cannot be achieved via appropriate nutrition and lifestyle choices... which is false!

Similarly, if you decide to buy vitamin supplements... research the ideal dosage first. In most cases... once you have achieved the daily recommended intake, there is little point in taking more of that vitamin. In some cases, you may even be at risk of reaching the toxic threshold... which is as bad as it sounds! Some vitamin supplements provide a dose many times larger than the daily requirement... so check labels carefully, or preferably speak to your GP/a dietitian first!

Exercise In General:

Living an active lifestyle in itself helps to maintain a healthy immune system.

Unfortunately, this still doesn't mean that keeping fit will ensure that you avoid all illness...

But it will decrease your risk in most cases.

It's all too easy to assess your health by looking in the mirror, stepping on the scales or keeping an eye on your clothes size.

Because 'weight' has become such a mainstream topic and common way of judging yourself...

A lot of people have fallen into the mistake of thinking that this is a reliable way of monitoring their overall health.

Don't get me wrong...

Maintaining a healthy weight is an important part of staying fit and healthy.

But there are other factors to consider.

In this case...

It's perfectly possible that you can maintain your target 'weight', predominantly through a diet based strategy.

But still practice a relatively inactive lifestyle.

And while you may argue that you achieved your weight and/or body composition goals...

You are missing out on the health benefits directly attributed to physical exercise...

Including the immune system benefits!

Aerobic Exercise & Strength Training:

Regular, moderate to high intensity exercise helps to stimulate the immune system by mobilising T-Cells. These cells play a major role in your body's ability to adapt to the threat of specific invading pathogens.

The important point here, is that this benefit relies on regular and fairly intense exercise.

So, you will need to pay attention to (by properly planning and monitoring) your intensity and total amount of exercise, to make sure that you are getting the most out of your programme.

A random, sporadic approach won't cut it.

The trick is to find your own sweet spot between doing enough to stimulate those T-Cells (and strengthen the immune system), whilst not over-doing it, and causing too much physical stress and/or not allowing enough recovery opportunity...

Both will cause a weakening of your immune system as your body struggles to cope with the demand that you place on it.

We call this search for the sweet-spot 'hormesis'.

While it applies to most physical adaptations to exercise...

Your immune system is a great example...

Do nothing...

Or not enough...

And you achieve no significant result.

You might maintain whatever you have already, or, more likely, you might decline in terms of whatever outcomes you were aiming to achieve.

As you gradually begin to increase the intensity/volume of exercise, you begin to enjoy the positive outcomes.

But continue to increase that intensity/volume too far, or remove your recovery windows...

And you cross the threshold into negative outcomes, by placing too much physical stress on your body and/or not allowing enough time to recover from that physical stress.

In terms of your immune system...

As we said already...

The 'sweet spot' of regular, challenging exercise, combined with adequate rest, will produce positive results...

Your immunity will be stronger, than if you had continued to do nothing.

But if/when you cross into 'over-training' territory...

Your immune system begins to weaken...

Potentially leaving you even more exposed to infection than you would have been with a sedentary lifestyle.

Hormosis graphic
Hormesis: The 'right' type and amount of exercise will help maintain a healthy immune system. But not enough, or too much, could result in the opposite... increasing your susceptibility to illness.

Yoga & Meditation:

Psychological stress, whether it's caused by work, relationships, work etc, has also been linked to reduced levels of immunity and greater risk of illness.

Yoga & meditation can help to reduce* stress levels and therefore reduce the physical responses to that stress. This includes the reduction of hormones such as cortisol, and hopefully helps to counter the risk of chronic inflammation.

*Reduces... that does not mean that it eliminates stress completely. Consider how you might avoid increasing stress levels (and the associated physical effects) in the first place... where possible!

These potential responses to stress play a part in lowering your immune systems' ability to protect you, just like the physical stresses associated with over-training and poor sleep (see below).

So while meditation in particular, gets a reputation for being a purely psychological and/or spiritual activity, it actually provides potentially vital physical benefits.

Another Reason To Fight Obesity...

Research suggests that obesity itself can negatively impact the immune system.

These negative effects are independent of the lack of activity that possibly contributes towards that obesity...

Therefore compounding the risks that already come with a low activity lifestyle.

Obesity contributes to the level of chronic inflammation in the body.

It is the ongoing, long-term exposure to that inflammation that compromises the immune system.

While solving obesity is not as simple as we would like, we obviously know that an active lifestyle and healthy diet are key parts of the solution.

So it makes perfect sense to make sure that those strategies, which are perhaps primarily designed to produce weight/fat loss, also have the effect of increasing immunity and therefore overall health.

Remember... a weight loss plan doesn't automatically tick all of the boxes of a immune supporting plan. Make sure you programme your exercise accordingly.

Note: While obesity will have a negative effect on your immune system in the long-term, studies show that regular exercise in the short-term WILL still provide positive benefits to immune function, regardless of whether you successfully lose weight or not. Obviously, reducing the amount of excess body fat would be ideal. But that is a long-term project. The point is, do not be put off by any perceived lack of visible progress... Individual exercise sessions (as well as contributing to longer term goals) will still provide immediate benefits, independent of any actual fat loss.

A Bit More On "Over-Training"...

While exercise is obviously an essential component of a healthy lifestyle...

There is such a thing as too much of a good thing.

Crossing the line into 'too much' exercise, as well as causing a series of other problems...

Can weaken your immune system...

Increasing your risk of illness.

The obvious irony is that you then end up doing less/lower quality exercise in the long run as you are forced to either reduce your exercise intensity or take an extended period off from training altogether.

It can be difficult to define what 'too much' exercise means as this would vary from person to person.

However you will probably be familiar with the common 'rules' that we encourage clients to follow...

  • when training at high intensity, allow 48 hours (minimum) recovery before training the same muscles again at high intensity. (You should not be programming two leg days in a row!)

  • try to avoid training sore muscles

  • programme adequate rest days (again, the optimum number will depend on the programme that you are following)

The important thing is to make sure that you are recovering from your workouts. If you are training at a genuinely high intensity, and/or fitting a very high total amount of exercise into a week, you will need to pay closer attention to this.

Even professional, full-time athletes have plenty of rest programmed into their training schedules.

Otherwise you may end up with a situation where you are overly stressing your body to the point where you are chronically exhausted and unable to "recharge".

If/when you notice that you are;

  • suffering from sore muscles on consecutive/most days

  • struggling to recover from minor injuries

  • feeling lethargic most of the time

  • catching regular colds

  • struggling to improve (or seeing a decline in) your workout performance

  • struggling to sleep

  • losing your appetite

... you might be over-doing it.

These are the warning signs that you are 'running yourself down'.

Stretching, pain
Look out for the signs of over-training. One of the risks is that you may weaken your immune system!

When You Are Unwell...

The above is supposed to help keep your immunity levels as high as possible, and hopefully prevent you from getting ill where possible.

But again, none of us can ever have 100% immunity to all illness.

Sooner or later, you are probably going to catch something...

And then you have to know what to do to optimise your recovery (or at least not risk making things worse!)

If in doubt, take a few days off from training...

You won't be doing any harm, and you'll probably speed up your recovery.

If the idea of missing a few sessions causes you to panic...

Look at it this way...

If you continue to train while feeling unwell, or return to training too early...

One of three things will happen;

  • you could become seriously ill (see below)

  • you may end up taking more time off from training in the long run if you never fully recover and keep yo-yoing between short breaks and full training mode

  • at best you''ll probably need to reduce your exercise intensity due to not feeling 100%... while you might feel that you are "battling through" your illness, you're actually just delaying your recovery. This could go on for a while. You may as well just take the time off and come back to full training intensity as early as possible.

The Risks:

Let's re-emphasise... You can't go wrong by scheduling some extra rest days. Your fitness isn't going to dramatically suffer if you take a week or so off to recover from a cold.

Frankly, if a week off does cause you to regress to a poor state of fitness, I'd question how much you had achieved in the first place!

For those who insist on trying to fight on...

The golden rule is...

Do not train if you have symptoms "below the throat".


  • chesty cough

  • muscle aches (make sure you know the difference between aches related to an infection and 'DOMS' caused by exercise)

  • fever/chills

  • upset stomach

Does this mean that you can exercise freely when your symptoms are "above the throat?"...

No... you will still need to use some common sense. Weigh-up the pros and cons of 'doing something' versus fully recovering as quickly as possible.

The worst case scenario when training with symptoms below the throat, is that you can place excess stress on your heart...

Which is obviously serious!

So taking time off in those circumstances is a rule.

"Above the throat" symptoms clearly still indicate that you are ill.

But usually won't pose the same immediate risk to your heart health.

So you have a little more room for judgement.

Although that doesn't change the fact that the safest thing to do (and probably best thing to do in terms of long-term results), is to take time off and recover as quickly as possible.

Other factors...

Don't forget...

The immune system is a complex system.

It doesn't have an on/off switch that determines whether you are going to get ill or not.

And exercise is definitely NOT the only factor that influences it's ability to function optimally.

Diet (including your micronutrient intake), various lifestyle choices (inc. alcohol, cigarettes, sleep quantity & quality), stress and much more also play a major role.

In other words...

Exercise alone doesn't come with any guarantees.

But if you do maintain the sweet spot of regular, moderate/intense exercise (with adequate rest)...

You're definitely making a positive contribution to a healthy immune system.