Intense Exercise Could Be Harmful to Your Health When Done Incorrectly
While it is widely known that regular exercise can improve health, reduce the risk of diseases, and extend life expectancy, there is a type of exercise that may have the opposite effect under certain conditions, and that is intense exercise.
What Is Considered Intense Exercise?
There is an indicator used to measure the intensity of physical activity called the metabolic equivalent of task, or MET. One MET would equate to the energy used to sit quietly. Different levels of exercise intensity are indicated by different MET values.
- Sedentary: MET values of ≤1.5; for example, sitting or lying down
- Low-intensity exercise: MET values of 1.6 to 3.0; for example, leisurely walking or standing in line at a store
- Moderate-intensity exercise: MET values of 3.0 to 6.0; for example, brisk walking, vacuuming, or gardening
- High-intensity/vigorous exercise: MET values of ≥6.0
High-intensity/vigorous exercise includes not only fast walking, running, and rope jumping, but also activities such as marathon running, triathlon, high-altitude or cross-country skiing, basketball, ice hockey, field hockey, rugby, handball, and high-intensity interval training.
General exercises such as walking and running increase in intensity as the speed increases. “Strenuous exercise could be walking at 4.5 miles per hour, jogging at 5 miles per hour, or running at 5.5 miles per hour,” said Barry A. Franklin, director of preventive cardiology and cardiac rehabilitation at Beaumont Health in Royal Oak, Michigan, and professor of internal medicine at Oakland University William Beaumont School of Medicine, in an interview with The Epoch Times.
The definition of high-intensity exercise varies depending on age and individual health status. Franklin stated that “some exercises that do not seem too strenuous can be challenging for an 80-year-old individual.”
While regular exercise offers numerous benefits, such as improving blood lipid levels, controlling insulin resistance, reducing cardiovascular risk factors, lowering the incidence and mortality rates of cardiovascular disease, as well as increasing happiness and life expectancy, high-intensity exercise may diminish these benefits and pose a risk to life in certain circumstances.
Excessive High-Intensity Exercise Can Lead to Cardiovascular Disease
Compared to low-intensity exercise, high-intensity exercise provides diminishing overall cardiovascular benefits and may lead to cardiovascular disease.
Franklin stated that vigorous exercise can cause an increase in heart rate and blood pressure, which may lead to irregular heartbeats or a heart attack. This is especially true for individuals who have a history of heart problems or are at risk of developing them, including those with atherosclerotic cardiovascular disease, coronary artery disease, structural heart disease, and hypertrophic cardiomyopathy, as high-intensity exercise can be fatal for them.
A study published in the New England Journal of Medicine examined 1,228 heart attack patients and found that the risk of having a heart attack within one hour after heavy physical exertion was 5.9 times higher compared to less strenuous physical exertion or none. Another study published in the American Journal of Epidemiology also found that the relative risk of having a heart attack due to vigorous exertion was 6.1 times higher compared to lower levels of physical activity or rest.
Another prospective study of 1,098 healthy joggers and 3,950 healthy nonjoggers in Denmark showed that compared to sedentary individuals, the risk of death decreased by 49 percent for light joggers and 62 percent for moderate joggers. It is worth noting that the risk of death for strenuous joggers was almost the same as sedentary nonjoggers, only 6 percent lower. Adjusted calculations showed that the all-cause mortality rate for moderate joggers was three times that of light joggers, and the all-cause mortality rate for strenuous joggers was nine times that of light joggers.
Another study of over 1 million women showed that compared to women who only did strenuous physical activity two to three times a week, women who did strenuous exercise every day had a higher risk of developing coronary heart disease, cerebrovascular disease, and venous thromboembolism.
Studies have shown that very high doses of exercise may increase the risk of atrial fibrillation, coronary artery disease, and ventricular arrhythmias. Excessive intense exercises can put a lot of stress on the heart, leading to cardiac enlargement, impaired heart function, and the release of certain substances that are detrimental to cardiovascular health, thus increasing the risk of sudden cardiac death, according to a review in the Sports Medicine and Arthroscopy Review.
Additionally, according to a paper in the journal Missouri Medicine, long-term intense exercise can produce a large number of free radicals, which accelerate atherosclerosis and can lead to endothelial dysfunction. The presence and quantity of calcified coronary artery plaques are important indicators for assessing heart disease. A 25-year follow-up study of 3,175 Americans showed that individuals who exercised three times more than the recommended guidelines (over 450 minutes of exercise per week) had a 27 percent higher risk of developing coronary artery calcification by middle age, compared to those who did not meet the exercise standards (less than 150 minutes of exercise per week). This was particularly pronounced in white individuals, who had an 80 percent higher risk of developing coronary artery calcification.
The Inflection Point of Exercise and Its Impact on Mitochondria and Blood Sugar
According to the Sports Medicine and Arthroscopy Review paper, there is an “inflection point” in the effect of exercise duration and intensity on human health. The Missouri Medicine paper stated that it is unnecessary to engage in vigorous exercise continuously for more than 40 to 60 minutes.
After surpassing the inflection point, the heart may begin to sustain damage, and metabolic issues may also arise.
“When we start exercising once or twice a week, everything looks fine, and the mitochondria improve glucose control,” said Mikael Flockhart, a doctoral candidate at the Swedish School of Sports and Health Sciences, GIH, in an interview with The Epoch Times.
“However, when we push ourselves too hard every day, then we get into this negative state,” and the benefit of controlling blood glucose is reversed.
Flockhart led a study that showed that, after a week of daily high-intensity training, the participants’ mitochondrial respiration was significantly reduced, and their glucose tolerance and insulin secretion were disturbed. “It is just a stressful situation where you do not get positive adaptation,” he explained.
Flockhart further explained that when someone begins training with overload, the body enters an unbalanced state, which can suppress the immune response and affect normal hormone secretion, leading to lower testosterone levels. Furthermore, the various stress factors that result from intense overload exercise can harm sleep quality and contribute to feelings of depression.
People Who Are at Higher Risk When Doing High-Intensity Exercise
Franklin emphasized that high-intensity exercise is not inherently dangerous and, when performed in a moderate manner, “higher intensity exercise is more beneficial for protecting the heart.” However, intense exercise can be fatal for some people.
1. Sedentary People
“Individuals who are used to prolonged sitting face the highest risk when engaging in sudden, intense exercise,” said Franklin.
Research has suggested that the least active and least fit individuals are at the greatest risk of experiencing exercise-related acute cardiac events. A database with over 2.9 million fitness members revealed that nearly half of exercise-related deaths occurred among members who did not exercise regularly or less than once a week.
2. People With Heart Disease
According to Franklin, many people are unaware that they have heart disease, and their risk of engaging in intense exercise is high.
Individuals who were active and healthy in their youth may have developed underlying cardiovascular disease over the past few decades without realizing it. Therefore, when these individuals, who are no longer accustomed to high-intensity exercise, participate in activities such as a basketball game, their risk of heart issues increases significantly.
Moreover, some busy adults may choose high-intensity exercise as a way to kickstart their fitness journey, thinking that it is more time-efficient and effective. However, it can be dangerous if such individuals have underlying cardiovascular disease of which they are unaware.
During the interview, Franklin mentioned a case he had encountered where a 38-year-old male nurse aspired to change his obese physique through exercise, but unfortunately died suddenly while running on a treadmill on his first day in the gym.
It is worth noting that approximately 38 percent of Americans aged 40 to 59 have cardiovascular disease (including hypertension, coronary heart disease, heart failure, and stroke), and this percentage rises to 73 percent in the 60 to 79 age group. Additionally, according to the U.S. Centers for Disease Control and Prevention, about one-fifth of heart attacks are silent, meaning damage is done without the person knowing it.
“It is for this reason that I always tell all middle-aged and older patients or adults starting an exercise program to start with walking,” said Franklin. He recommended that people start with a gradual walking training program for two to three months before transitioning to running.
How to Exercise in Moderation
Franklin put forward four exercise plans that incorporate walking.
- For elderly people with poor physical condition, it is recommended to walk four days a week at a comfortable pace of 2 miles per hour for one hour per session.
- For relatively healthy individuals, it is recommended to engage in moderate-intensity exercise three days a week, such as walking at a pace of 3 miles per hour for one hour per session.
- For relatively healthy individuals, another moderate-intensity plan is to walk for 30 minutes or longer, five or six days a week, at a pace of 2.5 to 3 miles per hour.
- Walk 7,000 steps a day.
Franklin provided further explanation for the final recommendation. While many people aim to achieve a daily step goal of 10,000, walking 7,000 steps per day is sufficient to attain specific health benefits. Franklin mentioned a major study published in the Journal of the American Medical Association in 2021, which found that individuals who walked more than 7,000 steps per day had a 50 to 70 percent lower mortality rate over the next 10 years compared to those who walked less than 7,000 steps per day.
Franklin noted that compared to walking, running can achieve the same benefits in a shorter amount of time. For instance, running for just five minutes may be equivalent to walking for 15 minutes.
Flockhart believes that for the average person to maintain good health, daily exercise should be of low intensity, and one or two sessions of high-intensity training per week are also acceptable. However, beyond three sessions, the benefits do not increase, and it can even interfere with regular low-intensity exercise. Moreover, the total duration for each high-intensity training session should not exceed 30 minutes.
“For maintaining good health, the training volume is the most important factor,” said Flockhart. Many people exercise intending to obtain more benefits from high-intensity workouts, but “it is not sustainable,” he said. For the average person, it is really difficult to maintain frequent high-intensity exercise, and therefore, it is crucial to find a healthy exercise routine that can be sustained in the long term.
“Relaxing activities such as jogging, cycling, and short walks are really enjoyable and allow us to appreciate nature. I think that is the most important form of exercise,” said Flockhart.
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