Does Running Have Side Effects On Your Body?

Health Risks Of Running

There’s no end to articles and studies endorsing running as the best activity for health. And why not? Running has proven beneficial in both curing and preventing various ailments across all ages, from high blood pressure to atherosclerosis and depression.

Having said that, is it possible that running is all good and no evil? Yes and no. Like any other exercise, running comes with its share of risks. But these risks turn into incidences when there are several factors at play: bad running form, poor bone and muscle condition, long-standing bad health habits, age, and even genetics, for instance.


Let’s analyze each injury or harm running is known to cause and see if running alone is responsible for it.

Improper Running Can Damage Your Muscles And Bones

When you run, you put maximum stress on the bones, joints, muscles, and soft tissues – together called the musculoskeletal structure – of the lower part of your body, especially the knee and the hip. Various studies show that most running injuries occur in the legs, predominantly, the knees.


Bad Running Form

In most cases, this is due to bad running form or accidental misalignment of the joints. There are also anecdotal evidences pointing to bad running shoes or the wrong terrain they chose to run on as reasons for knee pain or injuries.

Overuse Injuries

About 50 to 75 percent of these injuries, however, appear to be due to overuse, where these body parts are subjected to the same kind of movement repeatedly, without proper rest in between. And unsurprisingly, there appears to be a 20 to 70 percent chance of these injuries recurring.1


And because long-distance running, especially without proper rest and nutrition, can be called a kind of overuse, your chances of getting injured increase when you run greater distances.


Another major contributing factor to running injuries is obesity. A study on the risk of injuries of obese vis-à-vis non-obese individuals found that obese individuals were at a higher risk of injury if they ran more than 3 km during the first week of their running program.2


The chances of these injuries recurring are also greater if there is a history of prior injury.3

Types Of Injuries

It has been seen that hamstring strain, which is a tear in the hamstring muscle, and tendinitis, which is an inflammation of the tendons, are most common in sprinters. Back pain and hip problems are most common in middle-distance runners, and foot problems are most common in marathon runners.4

  • Ligament tears: These happen especially in the knees and ankles, where it is called an ankle sprain, because of a sudden stress caused by improper landing or an abrupt halt.
  • Runner’s knee: This causes soreness and discomfort beneath the kneecap or to one side of it and can be attributed to different causes like overuse, misalignment of the bones, and a sudden blow to the knee.
  • Shin splints: These are micro-tears and inflammation in the tissues around the shin bone caused by too much physical exertion too soon, such as suddenly increasing the mileage or switching to a tougher terrain.
  • Ankle sprain: This happens when the ankle is rolled or twisted such that the ligaments in it are stretched and torn. It can cause pain and swelling and restrict the range of motion.
  • Achilles tendinitis: This happens when the Achilles tendon that connects the heel bone to the calf muscle is inflamed because of overuse or wrong form.
  • Plantar fasciitis: This is an inflammation of the tissue that runs across the bottom of the foot, connecting the heel bone to the toes. The causes can be too much pressure on the heel, obesity, or a rigid Achilles tendon.

Does Running Reduce Your Bone Density?

Several studies have reported that male endurance runners have lower bone density than those who do not run and those who run shorter distances. One of those showed that male long-distance runners who averaged 92 km per week had 9.7 percent lower bone density in the lumbar spine than a group of non-runners.5

Yet another showed that male long-distance runners had reduced bone mass and increased bone turnover compared to others, which suggests accelerated bone loss for runners running long distances.6


Similarly, female endurance runners also had lower bone mineral density of the lumbar spine, which was correlated with the distances they ran.7 Lower bone density is dangerous, because as high-impact, fast-moving exercises such as jumping, running, jogging, or skipping increase compression in the spine and the legs, the bones become more prone to fracture.

But recent research claims otherwise. It says weight-bearing exercises like running actually help increase the bone density in your legs. And no matter whether you are male or female, the greater the race distance, the better the bone stiffness, which is a measure of bone density.8 Professor John Tobias at the School of Clinical Sciences, University of Bristol, claims that high-impact activities increase hip bone density in adolescents, especially males.9


Increasing the bone density early on helps counter the age-related bone decline later, especially in women as their estrogen – a hormone responsible for good bone health – levels drop after menopause.

Can Running Damage Your Heart?

Exertion Can Trigger Heart Attacks, But Is It The Only Cause?

Heart attacks during or about an hour after running or jogging aren’t unheard of, especially when people who do not usually exercise undertake heavy physical exertion.

But in one study, researchers found that heart attack was induced by heavy physical exertion in only 3.8 percent of the cases they studied. In such cases, the researchers suggested, gradually increasing the levels of daily physical activity can progressively lower such risks.

But then, they found that people with moderate exertion also showed signs of myocardial infarction—the medical term for heart attack. This indicates that physical exertion cannot be considered as the only trigger. The researchers suggested that even stress or anger could trigger such symptoms.10

Do Runners Have Thick Heart Valves?

A 2011 study on the long-term effects of exercise found that there was an unexpectedly high degree of thickening of the heart valves in healthy, lifelong veteran male athletes. Almost 50 percent of the men had this condition, medically known as myocardial fibrosis, but without any symptoms. There were no such cases in young athletes and test subjects who did not exercise. This data does suggest that veteran athletes have a higher prevalence of non-severe heart disease, which may increase the risk of exercise-induced heart failures.11

But this study was limited to only 49 people, among whom there were only 12 athletes.

Are Their Heart Chambers And Arteries Stiff Too?

Well, it seems so, going by this study that claims that excess endurance activity may increase the risk of cardiac abnormalities, such as fibrosis and stiffening of the atria, or the upper chambers of the heart, the right ventricle, or the lower right chamber, and the large arteries. This may in turn increase the risk for long-term illness or death.12

But the catch here is the word excess. The study does mention that all the markers of a potential heart damage are increased during the training of excessive endurance exercises like marathons or ultramarathons, but everything returns to normal in a week. It’s when this happens for months and years, some runners develop patches of fibrosis or stiffened heart chambers. The study also mentions that this finding is still not conclusive because there are inconsistencies in the report findings.

Can Running Compensate For Other Lifestyle Factors?

One major drawback of all these studies was that they had not isolated the health risks posed by running from those posed by lifestyle factors. A 2014 study sought to address this issue by conducting a study on whether running reduced the risks of atherosclerosis of the carotid artery in marathon runners and their spouses or partners who had similar lifestyles.

The results showed that the runners had lower BMI, lower triglycerides and low-density cholesterol (the “bad” cholesterol), and lower heart rate—all of these are risk factors of atherosclerosis.

But running did not make them immune to the aspects of the disease that were related to age, long-standing bad health habits, and a family history of heart diseases.

However, the researchers did not find a direct correlation between the distance they ran and the pace of running to the level of plaque in their arteries.13

In conclusion, you can say that moderate running does improve heart health but may not protect one from the ill effects of bad health habits, genetic tendency, and age-related decline.

Can Running Damage Your Kidneys?

Strenuous exercise, including marathon running, can damage the skeletal muscle cells in a process known as exertional rhabdomyolysis. When the muscle is damaged, a protein called myoglobin is released into the bloodstream. If it is released in high concentration and the body is dehydrated or under heat stress, myoglobin collects in the kidneys. There it breaks down into substances that can damage kidney cells and lead to acute kidney failure.

But there’s a catch here too. A study reveals that such cases of kidney failure in marathon runners are not very common. And when the kidney failures did happen, it turned out that the runners had either taken analgesics or were suffering from a viral or bacterial infection or a pre-existing condition like heat stress, dehydration, or latent myopathy—a disease of the muscle tissue.14

Like we said, running has many risks associated to it if done recklessly. But with proper precautions, these injuries can be prevented. Do not lose out on the benefits of running fearing injuries.

Do it with caution, under the guidance of a trained runner, and remember the mantra: moderation.