Too Much Cardio Can Cause More Harm Than Good

Do you dread going to the gym for what feels like hours at a stretch? Or do you avoid working out altogether because you just don’t have the time? Then what I’m about to tell you should be music to your ears: sometimes when it comes to exercise, less is more.

It’s becoming increasingly clear that too much exercise, particularly long bouts of cardio, can cause more harm than good.

And while most Americans would be well served to exercise more, there’s probably no need to work out for more than 45 minutes or so at a time, as long as you exercise correctly and efficiently. In fact, one of the most effective exercises I know of takes just 20 minutes for the whole workout (I’ll explain more below)…

When Good Exercise Goes Bad…

Getting your heart pumping with regular cardio exercise is important. As your heart rate rises, the amount of oxygen in your blood improves, and endorphins, which act as natural painkillers, increase.

Meanwhile, aerobic exercise activates your immune system, helps your heart pump blood more efficiently, and increases your stamina over time. But there is a cut off point to these benefits, and if you push your cardio session too long it can actually harm your body, leading to:

A catabolic state, in which your tissues break down
Excess cortisol (stress hormone) release, which not only contributes to catabolism but also chronic disease
Microscopic tears in muscle fibers (which will have trouble healing if you continue over-exercising) and increased risk of injuries
A weakened immune system
Insomnia, especially if your workout is in the afternoon or evening

Research emerging over the past several years has now given us a whole new understanding of what your body requires in terms of exercise, and many of our past notions have been turned upside-down. It’s now clear that exercising too much can be a serious blow to your health.

Too Much Cardio Can Even Damage Your Heart

One of the best examples of the risks of over-exercising can be gleaned from marathon runners. Running a marathon is often seen as the epitome of fitness and the ultimate show of endurance. But it puts an extraordinary stress on your heart.

According to a study presented at the Canadian Cardiovascular Congress 2010 in Montreal, regular exercise reduces cardiovascular risk by a factor of two or three. But the extended vigorous exercise performed during a marathon raises cardiac risk by seven-fold! Long-distance running also leads to high levels of inflammation that may trigger cardiac eventsi and damage your heart long after the marathon is over.

In a study published in the Journal of Applied Physiology,ii researchers recruited a group of extremely fit older men. All of them were members of the 100 Marathon club, meaning athletes who had completed a minimum of 100 marathons. If running marathons provided cardiovascular benefit this would certainly be the group you would want to seriously examine. So what did they find?

Half of the older lifelong athletes showed some heart muscle scarring as a result, and they were specifically the men who had trained the longest and hardest.

Research has also revealed heart scarring after elite cardio training. Published in the journal Circulation,iii an animal study was designed to mimic the strenuous daily exercise load of serious marathoners over the course of 10 years. All the rats had normal, healthy hearts at the outset of the study, but by the end most of them had developed “diffuse scarring and some structural changes, similar to the changes seen in the human endurance athletes.”

Yet another study showed that long-term endurance athletes suffer from diminished function of the right ventricle of the heart after endurance racing.iv They also had increased blood levels of cardiac enzymes, which are markers for heart injury, and 12 percent of the athletes had detectable scar tissue on their heart muscle one week post-race. So it is more than likely that if you over-exercise you will do your body great harm.

Ideally, to get the most benefits you need to push your body hard enough for a challenge while allowing adequate time for recovery and repair to take place. It turns out that one of the best ways to do this is to follow a fitness regimen that mimics the movements of our hunter-gatherer ancestors, which included short bursts of high-intensity activities — but not long-distance running such as is required to complete a marathon or even an hour on the treadmill.