What Does Running Do to Your Body?

In general, runners have stronger hearts and better lung function than non-runners, according to a November 2018 study in Frontiers in Physiology. Runners have a lower resting heart rate, better oxygen intake and higher cardiac output (the amount of blood the heart pumps per beat).

And that's important because your cardiovascular health is a predictor of life expectancy and disease risk. In fact, an April 2013 study in Heart found that every 10-beat-per-minute increase in resting heart rate correlated to a mortality-risk increase of 16 percent.

A heart that has to beat faster has to work harder. During exercise, that's expected. But at rest, that's a sign your heart doesn't have the strength to pump enough blood with each beat.

Physical activity, like running, stimulates enzymes that help move low-density lipoprotein (LDL, a.k.a "bad" cholesterol) from the blood to the liver so it can be excreted.

Jogging also helps increase the "good" cholesterol (high-density lipoprotein or HDL). A landmark study published in March 1982 in the Journal of Cardiac Rehabilitation found that the amount of miles run each week directly correlated with levels of HDL cholesterol. This acted as the foundation for the research to come, which supported these findings.

Improving your cholesterol levels reduces your risk of blood clots, stroke, high blood pressure and heart disease, per an April 2013 study in Blood Pressure.

Beyond cholesterol, running can help improve all components of metabolic health—blood sugar levels, triglycerides, blood pressure and body weight.

An April 2021 meta-analysis in Sports Medicine found that just a single bout of aerobic exercise significantly decreased insulin levels and increased glucagon concentrations. The effect of this is well-regulated blood sugar levels, an indicator of good health.

And it can increase insulin sensitivity for at least 16 hours after physical activity, per a January 2000 study in the International Journal of Sports Medicine. Lower insulin sensitivity, also known as insulin resistance, can be dangerous, as it's a precursor to type 2 diabetes and obesity.

If your goal is weight loss, running increases your energy expenditure to help achieve a calorie deficit. According to Harvard Health Publishing, a 70-kg person running 5 miles per hour will burn 576 calories per hour.

And if you do certain types of running, like HIIT (high-intensity interval training), you'll be able to burn calories even after you stop running thanks to exercise post-oxygen consumptions (EPOC). Doing max-effort sprints followed by periods of rest or active recovery means your body needs extra time after your workout to return to a resting state.

Also, when you run or jog consistently, you build muscle mass, which boosts your resting metabolic rate, as your muscles require more energy (calories) than fat. And building muscle while losing fat improves body composition (the ratio of body fat to muscle).

Weak bones are brittle and easily broken. This is particularly common among older adults, since people experience peak bone mass at 30, which gradually decreases with age. You can counter this age-related decline by exercising regularly.

When your body works against resistance during exercise, it's forced to protect itself by building bone density. As a February 2019 study in the Journal of Exercise Rehabilitation concluded, long-distance endurance running increases markers of bone formation.

When you run, your heart rate and body temperature increases. An elevated heart rate increases blood flow, helping clear bacteria from your airways, according to a July 2020 study in Clinical and Experimental Medicine.

And a higher core body temperature helps fights off infection and prevents bacterial proliferation, per MedlinePlus. You'll also experience an increased number of white blood cells and antibodies—both key markers of immune health—per a February 2013 study from the World Journal of Experimental Medicine.

You may have heard of "runner's high". It refers to the euphoric feeling people experience after a run. But it has actual scientific backing.

While running, feel-good endorphins are released. Endorphins are analgesics, meaning they reduce the perception of pain and trigger a positive feeling similar to the effects of morphine, per a January 2015 review in Frontiers in Psychology.

Running also releases dopamine, a mood-enhancer linked to the brain's pleasure and reward systems, according to a January 2016 study from Frontiers in Psychology.

Beyond a short-term mood boost, a June 2018 study in BMJ Open Sport and Exercise Medicine, showed that a 12-week running programme for people with mood disorders helped decrease symptoms of depression and anxiety.

Brain-derived neurotrophic factor (BDNF) is a brain-enhancing molecule released during running. In an April 2017 study in Frontiers in Psychology, a group of adults with cognitive impairment experienced improved executive functioning with aerobic exercise.

The increased blood flow around the body and brain that happens during a run means more oxygen and nutrients being delivered to the brain. This can stimulate neurogenesis, the production of new brain cells.

Plus, the size of the hippocampus—the region of the brain associated with learning and memory—actually increases as the result of a regular workout routine, per a February 2011 study from the Proceedings of the National Academy of Sciences.

Any form of exercise can help lower stress. But running has a few added benefits. Moving your entire body in repetitive movement can help you get out of your head and into your body, becoming more present and mindful.

In fact, a November 2018 study in Acta Psychologica found that going on a one- to two-mile run improved mood, decreased stress and boosted cognitive performance better than participating in a meditation session.

These benefits are compounded by running in the great outdoors. According to a September 2019 study in Mental Health and Prevention, exercising outside results in a greater reduction in stress than exercising indoors while also boosting perceived well-being.