Are your workouts too intense? Pros and cons of intense exercise

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Does excessive exercise exist?

For most people, the response is a big NO. In developed countries, we eat too much, sit too much, and center our life around sedentary activities. Framed this way, excessive exercise does not exist. Most of us benefit from more walking, more running, more biking, and more weight-lifting, any time of the day.

What happens if we don’t listen to our body and try to push our limits? Let’s go through recent studies to see the consequences.

First, intense exercise is usually defined by prolonged exercise at more than 85% of our maximum heart rate. For example, a 35 year old male would typically have a maximum of 185 beats per minute (bpm). 30mn of running, boxing or biking at more than 157bpm is a session of intense exercise. A common formula to get your maximum heart rate is 220 – your age. This is also equivalent to zone 4.5 to zone 5 on a watch with a heart rate monitor. This can give you a rough estimation if you usually do moderate or intense exercise.

Past the definition of intense exercise, results differ greatly, depending on what you are looking at.

Benefits of Intense Exercise

In a 2016 study spanning 25 years involving n = 3050 in elderly Finnish, vigorous exercise was associated with lower cognitive deficit, with an odds ratio of 0.50, meaning elderly people participating in regular intense exercise were twice less likely to get a disease such as Alzheimer or dementia. The odds ratio of 0.50 is much better than those reported for moderate exercise.

A smaller study added that intense exercise, especially cycling, improved cognitive performance after exercise. In simpler terms, it means those who did vigorous cycling were found to be sharper, and able to remember more and do more mental tasks.

Intense exercise also improves sexual function (or erectile function) in men, regardless of the race. This was concluded in a study involving 295 men. It was also found that those participating in less intense exercise did not see improvement of sexual function.

So far, we can see that intense exercise can improve brain and sexual function.

There are however clear negative consequences.

Detriments of Intense Exercise

In a study following 3293 elderly participants during 17 years, it was found that those involved in vigorous exercise had 30% higher risk of cardiovascular mortality. Those with regular moderate exercise had however 7% reduced risk of cardiovascular mortality. Even if you do not have a history of stroke or heart disease, this means vigorous exercise can be a risk for your heart.

While vigorous exercise is beneficial for men’s sexual health, it is a risk for women. A study examining 2,232 women undergoing in vitro fertilization (IVF) found that women who engaged in cardiovascular exercise for 4 hours or more per week for as little as one year prior to the treatment had a 40% decrease in live birth rate (OR .6; 95% CI .4-.8), as well as higher risks of cycle cancellation (OR 2.8; 95% CI 1.5-5.3) and implantation failure (OR 2.0; 95% CI 1.4-3.1). Another 2013 study following 3,628 women showed that women substituting vigorous physical activity to moderate physical activity may improve their fertility.  While vigorous exercise is beneficial for men, it has however negative consequences for women’s sexual health.

Why would intense exercise be detrimental for our health? Moderate exercise attenuates lymphocyte apoptosis, possibly by improving our body’s anti-oxidative capacity. Strenuous exercise generates however a series of more complex biological changes; however, evidence is sufficient to suggest that it increases free radical production that leads to oxidative stress, lactate accumulation, impaired mitochondrial accumulation. This means that past a certain stage, vigorous exercise creates too much oxidative stress that our body cannot undo, possibly increasing risk of diseases such as ALS. A study reported that Italian footballers, characterized by high aerobic effort and a high proportion of lean body mass, were at “severe increased risk of ALS“. Other studies following varsity college athletes, road cyclists, professional basketball players suggest similar results, suggesting that strenuous exercise can indeed increase risk of ALS. There’s also the risk of sudden heart attack, as reported above.

Are your workouts too intense?

We are always told : “More is better”. So people run faster, longer, or try to break weight records.

If you know your maximum heart rate, monitor vitals, and also make sure to have enough rest & recovery, more can be better. Go run faster. Try squatting more. I do it myself once a week, for fun.

However, if you are elderly (even without a history of heart disease), if you are a woman, or if you are a professional athlete, know the facts : vigorous exercise leaves traces. Moderate exercise will bring more substantial health benefits, for a long balanced life.

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