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respiratory tract infections in athletes

Why Athletes Might Be At A Greater Risk of Respiratory Tract Infections

 

Athletes who push their bodies to the limit often find themselves battling more than just physical fatigue—they’re also more prone to respiratory tract infections (RTIs) like the common cold. It’s a strange phenomenon, considering that moderate exercise is known to boost immune function, but when you cross a certain threshold with intense, prolonged training, the risk of getting sick goes up. This isn’t just anecdotal either—there’s real data backing it up.

Let’s dig into some of the research that suggests athletes with high training volumes experience illness more frequently than those with more moderate routines. But before we dive into that, let’s make one thing clear: exercise is absolutely great for you. It’s been shown time and again to reduce the risk of non-communicable diseases like cancer, heart disease, and chronic inflammation. It even lowers the risk of viral and bacterial infections—up to a whopping 67% reduction in upper respiratory tract infections for people who exercise regularly.

But here’s where things get weird: while moderate exercise keeps you healthy, pushing your body with prolonged, intense exercise can flip that script. The deeper you go into the pain cave, the more likely you are to end up sick.

The Dark Side of Intense Training

Research spearheaded by Dr. David Nieman, who’s basically the godfather of studies on exercise and illness, showed that intense training can actually depress immune function. In one of his landmark studies, Nieman monitored 2,311 runners prepping for the 1987 Los Angeles Marathon. A staggering 42% of the runners reported getting sick in the two months leading up to the race. Those running over 60 miles per week had double the risk of getting sick compared to those logging under 20 miles. It wasn’t just the training volume either—the marathon itself seemed to break down immune defenses, with 13% of runners falling ill right after the race, compared to just 2% of those who trained but didn’t race.

Elite Athletes and Higher Illness Rates

Nieman’s work isn’t the only research out there. More recent studies back up the same idea: elite athletes, who train hard and often, seem to get sick more frequently than recreational athletes. A study by Spence et al. looked at 32 elite athletes and found that they experienced a significantly higher rate of upper respiratory infections compared to recreationally competitive athletes.

So why are some of the fittest people on the planet getting sick more often than your average weekend warrior?

Why Do Hard-Training Athletes Get Sick?

The answer may lie in the body’s stress response. Intense, prolonged exercise jacks up levels of cortisol, a stress hormone that’s known to mess with your immune system. High cortisol levels can inhibit white blood cell function, mess with cytokines (the proteins involved in immune responses), and reduce the production of T-cells, which are essential for fighting infections.

To make matters worse, the number of immune cells in your blood actually drops dramatically after intense exercise. So, while your immune system is kicking into high gear while you’re training, it crashes hard once the session is over, leaving you more vulnerable to infections.

But it’s not just the exercise itself—there’s a lifestyle component too. Intense training often comes with mental stress, lack of sleep, and subpar nutrition—all of which can hit your immune system hard. Many athletes juggle training with demanding jobs or personal lives, and it’s easy to see how burnout can creep in.

Does the "J-Shaped Curve" Hold Up?

In the 1990s, Nieman proposed the J-shaped curve to describe the relationship between exercise intensity and illness. The curve suggests that while moderate exercise lowers the risk of infections, pushing into extreme training dramatically increases that risk. This idea has held strong for decades, but more recent research is challenging it.

A study by Martensson et al. found that elite endurance athletes actually reported fewer sick days the more they trained—up to a point. Training volume between 400-700 hours per year seemed to correlate with fewer illnesses, but once athletes exceeded that range, the risk of getting sick began to creep back up.

So, are elite athletes more likely to get sick or not? The answer isn’t crystal clear, partly because many of these studies rely on self-reported data. One study tried to address this issue by using throat swabs to confirm whether self-reported cases of illness were real infections. Turns out, many athletes who thought they had infections were actually dealing with non-infectious symptoms like allergies or exercise-induced irritation.

Overtraining and Illness: The Real Culprit?

It’s possible that the real issue isn’t just training volume, but overtraining—when athletes push past their body’s ability to recover. Overtraining can crush the immune system, leaving athletes vulnerable to illness. But elite athletes, who are typically more in tune with their bodies and their recovery, might be better at avoiding full-blown overtraining.

Think about it: an elite athlete who misses just a couple of days due to illness is still training at a high level most of the time. In contrast, someone who frequently gets sick, misses weeks of training, and struggles with poor performance is going to fall behind quickly.

How Can You Stay Healthy?

If you’re a competitive athlete logging serious hours, keeping track of your training and illness patterns is key. Try keeping an illness log alongside your training log. At the end of the month or year, look for patterns. Are you getting sick after heavy training blocks or big races? If so, it might be time to adjust your training load or recovery strategy.

Periodization—alternating between high-intensity training phases and planned recovery phases—can help you avoid overtraining and keep your immune system strong. And don’t forget about nutrition. A solid diet with the right balance of protein, carbs, and fats will keep your body fueled and ready to bounce back from tough sessions.

The Bottom Line

Exercise is a double-edged sword when it comes to your immune system. Moderate training keeps you healthy, but overdo it, and you might end up sidelined with a nasty cold. The key is balance. Train hard, but give your body the recovery and fuel it needs to stay in fighting shape.

 

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