In general exercise is good for boosting immunity, but too much of it (too much too soon, or particularly long or intense training sessions) can depress the immune system and make us more susceptible to infection. So it’s always important to pay attention to our diet, as well as to recovery to make sure that we’re not putting ourselves unnecessarily at risk of getting ill.
But despite our best attempts, sometimes the inevitable happens and we catch something. If this happens you’re almost always better taking a break from any hard training and prioritising getting well. If you’re ill your immune system will already be stressed trying to fight the infection. Training is adding another stress on your body and your body will divert resources from trying to get well into recovering from training.
Yes there’s the old rule of above and below the neck, and if it’s below the neck then certainly avoid exercise. But even if it’s above the neck, stay away from hard sessions. If you feel up to it then light exercise (at a low enough intensity that you’re not getting out of breath) can help you feel better, but be guided by how you feel. If you want to stay at home underneath the duvet then that’s probably the best place for you.
And if you’re not sure, check your resting heart rate first thing, to see if it’s different to normal and then keep an eye on your heart rate in the session, again to see if it’s different to what you’d expect for that intensity.
Clients always say to me ‘but I’m worried about losing fitness if I don’t train’. I completely understand the fear, but the risk is that by adding more stress to a body that is already trying to fight off a nasty bug, you delay recovery and end up taking more time off in the long run.
Plus whilst you are valiantly battling on and training through, if you’re ill you probably won’t be training at full capacity, and so your training session will be less effective. So from a training perspective you’ve achieved little other than risking prolonging the illness (and if training inside, spreading your germs around in the process).
So play it safe, if you’re desperate to do something, keep it nice and light, get the blood flowing but no hard efforts or anything too long. And then check my blog on Returning to training after injury or illness to know if you’re ready to get back on it and how to adapt your plan.