The first thing you need to identify is, what kind of sickness are you dealing with?
If it’s in your head (i.e an Upper Respiratory Tract Infection (URTI), a cold, runny/blocked nose, sore throat, headache, sinus congestion) then you should be fine doing some light exercise. In fact, it's likely a low intensity walk will do wonders for your health. It will help to lower cortisol levels, improve your insulin sensitivity, and ultimately mitigate the harmful effects of sitting/lying down all day. Another option is to do short sets of low reps, just enough to stimulate muscle tissue without elevating your HR too high. Even a few sets of barbell curls and shoulder press at home with a barbell, dumbbell, or AUSfit Torsion Bar is a great option as long as you keep your heart rate and RPE (rate of perceived exertion) nice and low.
On the other hand, if your sickness is below the neck (i.e. in your chest/lungs like a Lower Respiratory Tract Infection, in your GI tract like gastro/diarrhoea/vomiting, or if you’re experiencing fevers, aches and pains) you’re much better off resting completely.
Sometimes being sick is actually a valuable time to rest and recover your musculoskeletal system. It can actually do the body immense good to take a rest from time to time especially if you’re training and breaking down your body day after day from intense workouts. But if you really feel like you need to get moving, instead of focusing on the physical effects of exercise like building muscle and burning fat, you need to shift your mindset and focus on the therapeutic medicinal effects of exercise. It makes it easier to get up and moving if you think of it like getting your daily dose of medicine.
If you’re suffering from a chronic disease like diabetes, cancer, heart disease, autoimmune conditions etc, exercise is your best friend. The therapeutic benefits have been documented in the literature over and over again. From walking through nature, to moderate exercise like resistance training, and even HIIT has been shown to be effective at managing, controlling, and reversing symptoms of chronic disease. Of course, talk to your doctor and Accredited Exercise Physiologist before commencing an exercise program.
Remember, exercise is an acute stressor. When you’re sick your body is already under a huge amount of stress and your immune system is working hard to fight the foreign invaders to get you well again. Adding too much high intensity exercise is like throwing petrol on the fire.
There’s a big difference between exercise and physical activity. Simply spending time in nature and moving your body has been proven to have an array of health beneftis. Get outside, walk through a park or across a beach, breathe in some fresh air and soak up some precious vitamin-d-producing sunlight. Whatever you do, stay out of the gym and show consideration towards your fellow gym-goers by not spreading your contagious germs around the place.
And of course, do not overlook to importance of nutrition. You should be flooding your body with nutrient-dense, real, whole food. Eat the rainbow. Focus on consuming an array of colours of vegetables and some fruit. Consider using a probiotic supplement (especially if you’re taking a course of antibiotics which I’d suggest you should try avoid at all costs unless you really need it). Fish oil and a multivitamin may be beneficial too. Keep hydrated. Drink lots of water and herbal teas (Fresh turmeric and ginger tea is great for immunity).
All in all, exercise (along with healthy natural food) will improve insulin sensitivity which will improve your glucose tolerance, releases feel-good hormones called endorphins, helps you sleep better which will aid in faster recovery, boosts your immune system to help fight invaders, and gives you an overall feeling of health and wellness. When you’re sick, exercise can be your best friend or your worst enemy but it depends on the type of sickness you’re dealing with and the type of exercise you choose to do.