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How To Avoid Getting Sick During Winter Training

BY Andy Blow

There is a fine line between the immunity-boosting effects and immunity compromising effects of training. Here’s your guide to toeing that line successfully.

Winter is upon us, and as the air temperature drops, you can bet your bottom dollar that an increased number of us will be missing training sessions with coughs, colds, sore throats, and the flu.

Understanding what you can do to minimize your chances of getting sick is a good idea so that you can avoid interruptions to your training over the off-season (or when your heavy training begins again).

Are Athletes More Susceptible to Getting Sick?

There’s a long-standing and widely held (though not fully proven) belief that exercising has a “J” shaped effect on the immune system and, by extension, on your susceptibility to picking up infections and illnesses.

The graph below (taken from a 1994 paper on the subject) illustrates this idea nicely:


The theory goes that when we do some moderate exercise, our chance of catching URTIs drops (presumably because of the positive effects light exercise tends to have on our overall health). However, as exercise intensity or training load increases beyond a certain point, your risk of getting sick increases. It can even begin to exceed the risk associated with doing no exercise at all!

In other words, athletes training lightly are better protected from coughs and colds than couch surfers. But those training very, very hard run an increased risk of getting sick.

This might be because demanding training creates physical damage in the body, which in turn causes a range of stress responses that leave the immune system compromised and our bodies more open to the infections, germs, and viruses that we inevitably encounter in day-to-day life.

Depending on the level of stress induced by a bout of exercise, it’s thought that the “window of susceptibility” can last anywhere from three to 72 hours after training or competition.

From personal experience, I’m convinced that I’ve experienced this “J curve” in action many times. I am — and always have been — way more susceptible to illness immediately after times of high stress, whether that be heavy training, big races, periods of stress at work, or lots of back-to-back travel. Conversely, I seem to be way more resilient when I’m just ticking over with a nice low level of training.

And there’s data to back this theory up too. For example, a study of participants in the LA marathon in 1990 showed that significantly more of those who competed in the race got a cold in the days after finishing than in a control group of runners who didn’t take part in the race.

What You Can Do to Minimize Your Chances of Getting Sick

Any war on illness ultimately needs to be fought on two fronts by athletes to be effective:

  1. Minimizing exposure to potential sources of infection (especially at times when the immune system is likely to be compromised).
  2. Keeping the immune system as strong as possible gives it the best chance of fighting off any infections you come into contact with.

1. Minimize Your Exposure

Minimizing your exposure to sources of infection primarily involves a lot of relatively simple and repetitive common sense safeguards, including:

  • Avoid contact or proximity to those who are obviously ill (runny noses, coughs, sneezing).
  • Regular hand washing and good personal hygiene.
  • Avoid sharing cups/water bottles and cutlery.
  • Steer clear of crowded areas such as public transport during rush hour.

These guidelines were taken from a very recent International Olympic Committee consensus statement on the subject.

Although this might be stating the obvious, I think it’s worth emphasizing that taking these precautions is especially important at times when your immune system is likely be at its most vulnerable, such as immediately after hard workouts, races, and during extended blocks of training.

Smashing out a hard interval session shortly before jumping on a packed rush-hour train to work might not be the best idea if you’re aiming to minimize the chance of getting ill.

Finding more sensible times to do your hardest workouts (where you can plan some recovery time immediately after) could pay dividends by enabling consistency in the long run.

2. Keep Your Immune System Strong

There are a number of key areas that come up in most experts’ recommendations for keeping your immune system strong. Many revolve around minimizing your body’s stress responses:

Get plenty of sleep

A good eight hours or so of quality shut-eye every night is a cornerstone of solid recovery and recuperation for all athletes. Naps and power naps during the day are also great if you have time to fit them in.

If you’re suffering from unavoidably disrupted sleep patterns, it’s important to consider modifying your training plan to make it less stressful (i.e., shorter and less intense sessions), especially on days when sleep has been compromised the night before.

Make Sure Your Nutrition Plan is Right

It’s a bit of a wishy-washy and overused term, but maintaining a “good balanced diet” is critical for keeping your body healthy and unnecessary physiological stress to a minimum.

It’s also very important to try to fuel training sessions and competitions with adequate carbohydrate intake to avoid bonking (hitting the wall and running out of glycogen), as doing so has been shown to increase the levels of stress imposed on the body.

This subject was tackled in a 2004 paper that concluded that taking in 30-60g of carbohydrates per hour during hard endurance training appeared to reduce the levels of the stress hormone cortisol released during and after training.

It also decreased measurable levels of immunosuppression in athletes undertaking sustained intensive exercise, so it seems that it would reduce your window of susceptibility to infection too.

Manage Your Overall Training Load

Because a high training load is stressful for the body (it needs to be to drive positive adaptation), careful planning and management of your program can help to maximize those adaptations whilst minimizing the chance of getting sick.

The things to consider here are:

  1. Building in a sensible progression of volume and intensity over time, rather than ramping training up too quickly, can leave you excessively tired and cause elevated body stress levels.
  2. Planning your hardest training at times when you’ll have the best chance to maximize recovery afterward, and when other life stresses are low.
  3. Have regular rest days in your program and plan proper recovery weeks during your training cycle.
  4. Working with a coach or mentor to help you work out your plan and get a second opinion on how much load to take on as well as how to progress that over time.

Monitor Signs of Overtraining

It’s a great idea to record things like morning resting heart rate, mood, performance and motivation in a training diary. If you record these metrics accurately and learn to read the signs your body gives you, this kind of information can act as an early warning system for when you’re starting to get tired and run down.

It’s then possible to modify training to back off the intensity or duration (or rest up completely) and avoid really running yourself into the ground. This is a huge problem in highly motivated athletes, and I remember as a young triathlete regularly trying to push through excessive tiredness and fatigue and ending up training myself into illness many, many times.

It’s another area where working with an external coach or mentor can really help as they can often look at what you’re doing from a less emotionally involved point of view and tell you to back off before you’d be willing to do so if left to your own devices.

Stay on Top of Your Hydration

Good hydration plays a couple of supporting roles in maintaining the immune system.

The first is that, believe it or not, your saliva and snot form a critical part of your body’s first line of defense against infection. They contain antibacterial enzymes that help kill off germs before they get a chance to enter the body. As dehydration can compromise the production of these fluids, it can lower this first line of defense.

Also, in the same way that running low on glycogen can increase general stress levels in the body, so can being chronically dehydrated. As such, the maintenance of a good hydration status helps keep your body happy and reduces the overall stress it’s under, keeping the pressure off your immune system as much as possible.

If you want help refining your hydration strategy, take this free online Sweat Test to get a personalized hydration plan tailored to what you’re training for.

So, there are a few ideas to help you avoid unnecessary illness during this winter training period. Of course, none of these tips is a magic bullet for staying healthy (as, sadly, there’s just no such thing), but when taken as a whole and applied methodically, they ought to give you a decent chance to stay healthier and hit 2018 in good shape.


Gleeson, M., Neiman, D., and Pedersen, B. (2004, Jan.) Exercise, nutrition and immune function. Retrieved from https://pubmed.ncbi.nlm.nih.gov/14971437/.

Nieman, D C. 1994, Oct. Exercise, infection, and immunity. Retrieved from https://pubmed.ncbi.nlm.nih.gov/7883395/

Neiman, D C, Johanssen, LM, et. al. 1990, Sept. Infectious episodes in runners before and after the Los Angeles Marathon. Retrieved from https://pubmed.ncbi.nlm.nih.gov/2266764/.

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About Andy Blow

Andy Blow has a few top 10 Ironman and 70.3 finishes and an Xterra World Age Group title to his name. He founded Precision Hydration to help athletes solve their hydration issues. He has a degree in Sport and Exercise Science and was once the Team Sports Scientist for Benetton and Renault F1 teams.

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