As Mike Gleeson, emeritus professor of exercise biochemistry at Loughborough University and the author of Eat, Move, Sleep, Repeat, explains: “Exercise boosts your circulation so millions of white cells (immune cells) enter your bloodstream, enhancing your body’s surveillance so it can better detect harmful microorganisms. Several studies have indicated that regular exercise reduces the risk of upper respiratory tract infections by 30-50 per cent.”
But Prof Gleeson has a couple of important tips to ensure your exercise regime helps rather than hinders your immunity.
First, don’t crash-diet: a healthy body weight is vitally important, especially given the apparent link between obesity and Covid-19, but rapid weight loss can depress immune function. Second, limit any increase in volume or intensity to 5-10 per cent per week to avoid stressing your body. So if you conquer your first 5km run this week, nudge it up to 5.5 kilometres next week, rather than striving for a full 10. In a separate paper for Exercise Immunology Review, Prof Gleeson and a team of experts also suggest protecting immunity by doing more short but high-intensity workouts rather than fewer, but more draining, endurance sessions.
If you are returning to exercise after suffering from coronavirus, Prof Gleeson advises you start with light exercise, keeping your heart rate below 120 beats per minute for 30-45 minutes. As you feel stronger, step up to moderate exercise, keeping your heart rate below 150 beats per minute for 30-60 minutes. Then gently increase the volume by 15 minutes per session. Always wait until your symptoms disappear before exercising and stop immediately if they recur.
But how can people avoid picking up illnesses and infections in the first place? “There are two things to consider when it comes to staying healthy,” explains Prof Gleeson. “One is to avoid coming into contact with the microbes, viruses and bacteria that cause various illnesses. The other is through improving nutrition and lifestyle behaviour like sleep efficiency.”
The first task seems simple enough: avoiding sick people and contagious door handles and regularly scrubbing your hands are habits with which everybody is now familiar. But Prof Gleeson suggests some exercise-specific additions. Never rub your eyes, nose or mouth when you’re jogging: it is easy to do when you’re sweating but is the perfect way to inoculate yourself with germs.
With indoor pools now open and many people enjoying ocean swims, Prof Gleeson suggests you wear goggles and ear plugs to prevent eye and ear infections, use flip-flops or swim shoes to avoid skin infections, and carry a hot drink in a flask to raise your core temperature after a cold dip.
Don’t share objects like bike pumps, tennis rackets or energy snacks with friends during socially distanced workouts. And always clean your bike seat and handlebars with soapy water when you get home to prevent your bike turning into a portable Petri dish of bacteria.
Staying hydrated when you exercise will boost your immunity as well as your performance. That’s because saliva contains special proteins with antimicrobial properties – including immunoglobulin A and lysozyme – which aid immunity. But make sure you wash your water bottle every day to prevent a build-up of germs. Prof Gleeson suggests you use boiling water and washing-up liquid and let the bottle dry naturally instead of using a tea towel which can easily get contaminated. Remember to scrub the inside with a brush to break down the grimy biofilm caused when bacterial cells multiply on moist surfaces.
To remove skin-irritating bacteria from your running gear, cycling Lycra or swimwear, turn your kit inside out when you wash it: this allows your detergent better access to the inner fibres where the bacteria, dead skin and oils get trapped. It is worth buying a special sports detergent: Halo, which is anti-fungal, antibacterial and antiviral at 30C, is specially formulated to clean tricky moisture-repelling sports fabrics like Lycra and nylon. And always wash your kit straight after exercise instead of allowing it to fester in the laundry basket.
Sweaty iPhone armbands, cycling helmets and yoga mats should be washed regularly with soapy water or spray-cleaned with a mild disinfectant, while headphones should be gently cleaned with a cotton swab.
Improved exercise hygiene will cut your risk of infections but what you eat before and after your workout will also affect your immunity. “Aim for colourful plates with lots of veg to get a good mix of the 46 essential nutrients to support immune function,” advises Prof Gleeson. “Fruit and veg also contain polyphenols and flavonoids, some of which have anti-inflammatory and antioxidant effects which could increase your tolerance to microbes.”
As a sample athlete meal plan, he suggests fruit with wholegrain cereal for breakfast; a mushroom, tomato and onion omelette for lunch; and fish with peppers, squash and leafy greens for dinner. There is also growing evidence that probiotics could reduce the risk of respiratory infections in active people.
Hard-working exercisers certainly shouldn’t avoid carbohydrates. “Ingesting about 40 grams of carbohydrate per hour of exercise helps maintain blood sugar levels and reduces stress hormones to limit any depression of your immune function,” explains Prof Gleeson. “And for optimal immune function, athletes also need more protein.”
He recommends 1.2-1.6 grams of protein per kilogram of body weight per day, as opposed to the 0.8 grams recommended for the general population. “If you do get infected your immune system will need more protein to produce antibodies and multiply the cell lines that will defend you against the pathogen.”
Prof Gleeson has a final warning: however fit you may be, if you don’t get enough sleep you will always be vulnerable. “One study found that people who get less than seven hours of sleep were three times more likely to develop symptoms of respiratory illness,” he explains. To improve your sleep quality, stick to a regular sleep schedule and use blackout blinds. “Avoiding infection is the big one,” concludes Prof Gleeson, “but regularly getting a good night’s sleep is one of the best ways for people to protect their immunity.”
The Telegraph, London
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