Post exercise immunosuppression: are you a sufferer?

You’re in the best shape of your life, so why do you keep getting ill? Well, you may be suffering from PEIS – Post Exercise Immunosuppression. Warren Pole discusses causes, symptoms and treatment


The harder you train, the fitter you become. Sleep patterns improve, stress levels drop and you go about your daily life with a spring in your step. In short, things are peachy. But it isn’t always like this. Because despite being fitter than much of the population, many athletes still catch more colds than the average sofa-surfing, takeaway-snaffling regular Joe. What gives?


The problem is Post Exercise Immunosuppression, or PEIS, which is where exercise increases levels of the stress hormones adrenalin and cortisol in the body. This is a basic stress reaction and exactly
the same as we experience under more traditional forms of stress like overwork, difficult emotional situations or plain old lack of sleep. This reaction knocks out your immune system temporarily, leaving you as weak as a kitten.

The level of exercise involved has to be high for this to happen. Moderate training won’t cause a problem, but when sessions go over two hours or intensity regularly steps above 85%, PEIS problems can occur. Endurance specialists like Ironman competitors and marathon runners are especially at risk. On average, you can expect to catch around three colds a year, but if you’re suffering more than this, PEIS could be the cause. 

“PEIS is a genuine problem,” says Gareth Evans, sports scientist at the Porsche Human Performance Centre, who deals with a number of elite endurance athletes. “It’s linked to overtraining, and is made worse by people training through it.”

In extreme cases, the symptoms can be life-threatening, as triathlon coach Joe Beer illustrates. “I was training a guy who kept getting ill. I recommended a break and didn’t hear from him for a while. I assumed he was taking it easy. Then I had a call from him in hospital. He’d carried on training and had ended up on life support with pneumonia. It had almost killed him.”

This is an extreme example, and as well as PEIS there was a severe degree of exercise addiction involved, but it makes the point that PEIS is a real concern for anyone training hard – although there’s no need to suddenly wrap yourself in cotton wool to avoid it either.

“The other extreme is stopping training at the first hint of a sniffle,” says Beer. “You’re not doing triathlon if you don’t like a bit of discomfort – it’s about pushing yourself and seeing what you’re made of.”

Treading the line

The first step is to realise not all illness is caused by PEIS. Three colds a year is normal, and this can go up or down for all of us in any given year. As Beer says, “It’s not called the common cold for nothing.” But if a pattern is developing over a couple of years or longer where you’re consistently more ill than people around you, or colds and bugs take forever to shake off, PEIS could be at work. And don’t think it can’t affect you because you’re not an elite. Age-groupers and amateurs are often at more risk than pros.

While some experts sniff at the idea of anyone around the seven-hours-per-week training mark being able to overdo it, that’s because they’re looking at it from a pro-perspective. After all, seven hours of training in a week is nothing to a top athlete. But the difference is amateurs in this band fit their training around lives often already packed – full-time job, kids to look after and no coach to monitor it all for them.

“Elites have it easier,” says Beer. “They can overdo it and then take a couple of rest days. But age-groupers can’t. Many think a rest day means simply not training. It’s not. A recovery day at pro level is doing absolutely nothing. Lying on the sofa all day, maybe having a massage.”

The first cornerstone is nutrition. “With the immune system it’s all about getting a varied diet,” says Evans. “We ask our athletes to self-monitor; everyone says they eat healthily, but when they keep a record of everything they eat, we often find their diets aren’t as good as they think. A balanced wholefood diet is what’s needed.”

PEIS preventionAs pro Tristan Shipsides puts it, “Try and eat as healthily as you can. I eat a lot of fruit and veg – the usual five-a-day plus antioxidants – and drink plenty of milk.”

After diet, watch your hydration. Mucus and saliva are two of the body’s best natural barriers against infection but both perform badly when you’re dehydrated, so plenty of water during heavy exercise is key, even more so afterwards when your immune system could be at its lowest.

Post Exercise Immunosuppression symptoms

“The key signs of PEIS are getting symptoms of a cold or sore throat and then not being able to shake it off,” says Gareth Evans. “Normally a cold should last a week, but with PEIS it will hang around a lot longer.

“Also feeling run down, sleeping badly, having an elevated heart rate, experiencing loss of appetite or weight loss – these are all signs that you’re worn out and could be suffering PEIS.”

Some people recommend using resting heart rate to determine whether they’re getting ill, but as Joe Beer puts it, “You have to have a very controlled environment in your life for your
heart rate to be relevant as there are so
many factors that can affect it. The fact that you’re getting a sore throat should be setting off the alarm bells, not waiting for your heart rate monitor to show something.”


The same goes for monitoring power output. Pros can maintain consistency here from session to session because their lives are more controlled, so a dip for them may mean illness. For the rest of us, the ups and downs of daily life will naturally alter our power levels, making fluctuations irrelevant.