Can exercise make you ill?

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Unless you’ve been hidden in a cave somewhere with no access to either the internet or other humans, you’ll know that exercise is now widely regarded as a wonderdrug. It improves heart and lung function; reduces blood pressure; helps us stay trim; aids good sleep; enhances self esteem and, a recent study suggests, can even help with long term memory (*).

But as with many other supposed wonderdrugs (red wine, aspirin and green tea spring to mind) it is possible to do damage when you overdose. This month a study published in The Journal of Strength & Conditioning suggests (*) we are more prone to illness and infection when we train too hard and too often.The study found that those who performed high intensity sessions more than three days in a row had a distinctly suppressed immune response in comparison to those who did just moderate intensity sessions.

Professor Greg Whyte, a former Olympian and lecturer in Sport and Exercise Science at Liverpool John Moores University (https://www.ljmu.ac.uk/) isn’t surprised: “It’s true that people who are regular exercisers tend to have a lower incidence of illness and disease, including coughs and colds, but we also know that arduous exercise like marathon running or obstacle course racing dampens the function of the immune system for somewhere around three days afterwards,” he says. “During this time it’s more important than ever to take the usual steps like washing hands, avoiding hand contact with the mouth eyes and nose and staying well hydrated (since saliva is one barrier against infection).

“I would almost schedule it in – 48 hours after the World Championships or a similar competition I’d be sick, sleeping 11 hours a night and have a really bad cold. That’s because I’d basically been running on adrenalin and a sheltered lifestyle for several weeks.”

Essentially there’s a difference between the immediate and long term effects of exercise on immunity, just as there are some, like professional athletes, for whom reduced immune function is just part of the job. Former international GB rower and World Championships competitor, Steph Cullen says: “Every single athlete that does a big competition always gets sick afterwards,” she says. “I would almost schedule it in – 48 hours after the World Championships or a similar competition I’d be sick, sleeping 11 hours a night and have a really bad cold. That’s because I’d basically been running on adrenalin and a sheltered lifestyle for several weeks. I wasn’t allowed to get on the tube for two months before competition for fear of catching something. Afterwards I could just tell that my immune system had been trying to keep me well, working at 120% and then afterwards it was like a release, the weight was taken off my shoulders emotionally and physically and mentally.”

It’s not just competitive athletes either – plenty of recreational athletes have similar stories. Elizabeth Reumont was running marathons at university when she first noticed a drop in her immunity. “For months I had a propensity to get colds, sore throats, low level joint pain or low grade headaches. Then I had pneumonia and didn’t realise it! I was still running and ended up breaking a rib from coughing.”

I’ve had my own fair share of exercise-induced illness too. Back when I was fitter than I’ve ever been, performing high intensity, competitive training sessions 5-6 times a week (with 1-2 days rest), I caught every cough and cold that was going. At the time I thought I was doing everything right: sleeping around seven hours a night, drinking plenty of water and eating lots and lots of greens. Yet I still got ill – not just upper respiratory tract infections but also other physical markers of becoming run down such as conjunctivitis and eye infections, cold sores, and achey joints. Once had flu that lasted not one but three whole weeks. Why? Because I returned to the gym too early when my body was still depleted. By contrast, for the last four months I’ve exercised more moderately 3-4 times a week (with 2-3 days rest) and not been ill once, my struggles limited to a dodgy shoulder and a naturally moody temperament.

I’ve learnt that more days off exercise can make a big difference to my overall health and immunity without having much negative impact on my fitness. In fact in many ways I’m stronger because my training is more consistent.

You don’t have to be a detective to figure out where the difference lies. Just like Cullen (now retired from competitive sport) and Reumont (now a yoga teacher), who have both calmed their training down and no longer get ill nearly so frequently, I’ve learnt that more days off exercise can make a big difference to my overall health and immunity without having much negative impact on my fitness. In fact in many ways I’m stronger because my training is more consistent.

There’s no doubt however that in an increasingly fitness-obsessed culture we are under societal pressure to exercise, constantly. For sporty, determined types, making enough space in the diary for rest can be remarkably difficult. “Many people have a high performance attitude to their careers, and lives, but it’s important to understand that high performance sport isn’t necessarily healthy for the body.” says Miguel Crespo, a sports scientist working for the International Tennis Federation (http://www.itftennis.com/home.aspx). “It’s not normal to train every day for hours. If you’re overdoing it your body gives you signs such as getting ill or injured and you need to listen to it.”

How much exercise is too much depends on the person says Crespo, who advises getting an exercise prescription from an expert: “Factors like how much sport you’ve done in the past, whether you were sedentary, a smoker, what activity are you going to be doing and the level of that activity, all have an impact on how your system will cope. Taking a ‘no pain no gain’ attitude will probably result in you doing more than your body can handle and ultimately cause burnout syndrome.”

We should be cautious therefore about fast and furious fitness trends such as CrossFit, Barry’s Bootcamp, Insanity and F45, as well as suffer-fests like triathlon, marathon and obstacle racing, whose fast-paced structure make it difficult to maintain any kind of connection with what’s really going on inside our bodies. Done once or twice a week and with due care, these kind of ‘all out’ efforts can help us burn off stress and fat but, done too much they can make us sick. The truth is that sometimes evolution just doesn’t work fast enough and our bodies haven’t evolved to differentiate between 100 burpees done at breakneck speed and a life-threatening race against a rhino. So next time you push it in the gym, take an extra rest day before returning. Your body will thank you for it.

– By Lucy Fry

First appeared in Sunday Telegraph.

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