How to use moderate training to boost immunity and reduce the risk of catching colds and viruses

If your training has been blighted by colds and flu, there may be more than bad luck at play. Research shows that intense periods of triathlon training can temporarily weaken your immune system, leaving you open to illness.

During hard periods of training, the body produces the hormones cortisol and adrenaline, which raise blood pressure and cholesterol levels and suppress the immune system. This effect has been linked to the increased susceptibility to infection.

The opposite effect has been shown among those who do regular moderate exercise. One study reported half as many colds among those who exercise for 40 minutes each day, compared to a similar group of sedentary people.

Therefore, in order to keep making fitness improvements and stay healthy, you need to get the optimal balance between “moderate” and “intense” periods of training. The following tips should help you get it right.

Look back 

If you keep a training diary you should record any periods of illness in addition to your training. Whenever you catch a cold, look back at your diary and see if there was a link. Viruses commonly occur after a fortnight of particularly intense training. A diary can help you identify these patterns and avoid them in the future by planning your training accordingly.

Non-training stress

Stress, poor nutrition and lack of sleep can all increase your susceptibility to viruses. These things are inevitable from time to time, and it’s important to take your foot off the gas to recover rather than push on through at a high intensity. Continue to train regularly, but do shorter sessions with fewer periods of intense activity. You probably won’t gain much fitness during these periods, but one thing’s for sure – overtraining will only make you lose the fitness you’ve been working towards building.

The 48-hour rule 

The most stressful workouts are those that combine high intensity with long duration. You may recognise these – they are the ones that leave you feeling useless for the remainder of the day. Following these workouts, your immune system will be suppressed for around the next 48 hours. During this time you should either rest completely or keep your exercise as light as possible, such as recovery spinning on the bike. If you do more, you’ll dig yourself a hole that could take a week or more to climb out of.

Take recovery weeks

Sometimes it’s hard to tell whether you’re fatigued or not, and ‘listening to your body’ is not always sufficient. When I coach triathletes I set them an easy week every third or fourth week of the month. This includes two days off, and lighter training on the other days. Stick to these lighter weeks as strictly as you do hard training. I also do this with my own training, and over the last 20 years this strategy has coincided with periods of improved consistency and fewer viruses.

Listen to your loved ones

They may not be athletes, but sometimes the people around you can tell when you’re over-tired, even if you can’t. So if your friend/wife/husband tells you to take a day off training because you look shattered, there’s a good chance they are right. I have ignored this advice several times in the past and have often ended up with a cold. Don’t make the same mistake!

Phil Mosley – Coaching Editor