Running is among the most accessible and widely adopted forms of physical activity. Some people start their day with a jog, while others worry about joint wear and heart strain. This article explores what running can do for the body and where it can help the most.
bones and joints
New runners often fear that running will trigger osteoarthritis because it places impact on the knees and other joints. Yet large-scale research involving more than 90,000 participants found that regular running reduces the risk of osteoarthritis and lowers the likelihood of hip replacement, largely due to the influence of healthier body weight. Meanwhile, other forms of exercise can carry a small increased risk, typically in the range of a few percent.
Another study noted that the force on the knee during running can be about three times that of walking. This is offset by time spent airborne and longer strides, resulting in a total load that is similar for the same distance whether walking or running.
Running also strengthens bone density. Analyses of marathoners, half-marathoners, sprinters, and non-athletes show that regular runners tend to have significantly denser bones than sedentary individuals. While bone density varies with gender, age, and diet, the difference remains even after accounting for these factors. The distance a runner tends to select does not seem to affect bone density in a meaningful way.
Runners commonly encounter runner’s knee, which is a cartilage issue around the patella or a tantal tendon irritation along the iliotibial tract. Localized knee pain usually points to cartilage concerns, while lateral pain suggests iliotibial band irritation. In either case, running should be paused until symptoms subside. Strengthening leg and hip muscles and maintaining flexibility through regular stretching can reduce the chance of relapse.
Physiotherapist Helen O’Leary emphasizes the importance of gradual adaptation. Bodies need time to grow stronger. It is possible to run without injury when limits are respected and when strength training is part of a routine, promoting balance in daily life.
Heart
The impact of running on the circulatory system is sometimes debated, especially when races end in tragedy. Yet a large analysis of health and lifestyle data from fifty-five thousand adults found that runners have a notably lower risk of premature death and heart disease, with lifespans extending by several years compared to non-runners. These benefits held true across age, gender, and lifestyle factors such as smoking and alcohol use.
Running can protect cardiovascular health during chronic stress. Researchers from a major medical center observed that aerobic activity, including running, can improve arterial stiffness that stress can worsen, suggesting heart-protective effects beyond daily activity. While some findings come from animal models, the implications for humans are supported by broader human studies.
For newcomers pressed for time, evidence from Canadian researchers indicates that very short interval jogging sessions under ten minutes can yield nearly as many benefits as longer, moderate-paced cycling sessions. This makes running a practical option for busy schedules.
Endurance running, however, can stress the body in ways that may reveal hidden risks, such as a genetic tendency toward thickened heart walls or coronary insufficiency. Some deaths in endurance races occur near the finish, when adrenaline surges but the heart may not receive adequate blood flow. Aging runners appear more prone to certain coronary changes, while younger athletes may experience rapid heart rhythms that require quick recovery to normal function.
There is also a tendency for athletes to underreport symptoms to loved ones or clinicians. Even healthy hearts can be stressed by intense training, as scar tissue can form in the heart with frequent ventricular stretch, potentially affecting rhythm. Detecting this often requires advanced imaging beyond standard tests.
When planning a long-distance race, a cardiologist consult is advisable. Despite high-profile cases, marathon fatalities remain rare, with the greatest risk often in the final kilometers when effort peaks and pacing falters.
Brain
Running activates the brain’s reward system, contributing to improved mood and resilience against stress and depression. This activity also supports memory and cognitive function, especially after intense bouts of running. Studies show that after sprinting, individuals exhibited improved word recall and higher levels of brain-derived neurotrophic factor and catecholamines, substances that support neuron growth and brain plasticity.
Research in humans aligns with animal data: voluntary running enhances neuron production in the hippocampus, a region essential for memory. In humans, physical activity supports memory, executive function, and the integrity of brain matter over time, with prefrontal cortex involvement linked to mood regulation and attentional control.
Additional findings indicate that running boosts blood flow to areas of the prefrontal cortex associated with planning and mood management. In experiments, participants performed better on tasks requiring these functions, such as tasks where the word meaning conflicts with its display. Volunteers also reported improved mood after running sessions.
Experts note that the coordination required for running engages neural networks that support balance and movement, which likely drives heightened activity in the prefrontal cortex and related regions. Beyond mood and cognition, running contributes to healthier blood pressure, improved glucose sensitivity, stronger blood vessels, and reduced risk of thrombosis. The key is to train wisely and avoid overloading the body or attempting marathon distances too soon.