I have been running recently and I’m spooked.
All too often, I’ve heard that running is devastating to your joints, causes long-term problems, causes muscle deterioration, and leads to purple tumors on the left side of your knees. How valid are these rumors? For this investigation, I won’t simply accept the typical answers of “I read a study…” or “there’s an article that says…” or “I promise there’s evidence.” Instead, I’ll dive into the actual scientific examinations of the long-term impacts of running. I need some clear evidence to soothe my psychological fear that I’m killing myself while running. It feels like it.
Running and the Cardiovascular System
A famous 2014 study followed 55,000 adults for over 15 years, and found that around 50 minutes of running each week correlates with a 30 percent drop in all-cause mortality risk and an average increase of three years in lifespan (source). These results were controlled for all types of running, regardless of intensity, distance, or speed. Persistent runners “had the most significant benefits” with 29% lower mortality from all causes and 50% lower mortality from cardiovascular illnesses. In another massive study with 156,000 subjects, researchers found that men running at least 40 miles a week were 26 percent less likely to develop coronary heart disease than those running just 13 miles per week (source). In general, the consensus is fairly strong that running even small distances regularly reduces mortality due to heart disease.
However, there is some evidence that intense endurance training – and by intense, I mean Olympic level – causes health harms. For example, athletes participating in the Olympic games between 2002 and 2008 reported an 8% prevalence of asthma (AHR), which is close to the prevalence in the normal population (source). However, significantly higher rates of asthma were recorded in endurance sports like cross-country skiers (17.2%) and triathlon athletes (24.9%). This correlation indicates that maybe intense endurance exercise increases the risk of asthma. However, if you’re not exercising at the intensity of Olympic athlete, you probably don’t have to worry too much about the results of this study.
Another investigation declared “long-term excessive endurance exercise may induce pathologic structural remodeling of the heart and large arteries” (source). Researchers found that after intense cardiovascular activity like marathons or long-distance cycling, the right atria and ventricle experience overloading that prevents the heart from functioning as well. Normally, these negative effects on the heart disappear after about one week. But after years of repeated stress, long-term defects like patchy myocardial fibrosis and other arrhythmias may appear in the heart. However, as the researchers admit, “this concept is still hypothetical and there is some inconsistency in the reported findings.” When viewed from a lifetime perspective, it’s well-established that consistent runners have better health outcomes and lower mortality rates than those who don’t engage in frequent intense cardiovascular activity.
Impact of Running on Muscles, Bones, and Joints
Many are concerned that if they run too often, the constant impacts and force on their legs will ultimately lead to arthritis or other joint and bone-related issues. In some cases, this is a legitimate concern. The more you weigh, the more force is applied to your joints when you run. Experts advise that new runners start out slow and work up their mileage as their body sheds weight and adapts to running (source). Additionally, if you have a problem that affects your gait, you can harm your legs and joints by running. People with excessive pronators or hyperextending knees are less able to absorb shock through their legs, making running less healthy.
But for most people, running does not negatively affect the bones or joints in the legs, and it does not cause osteoarthritis. Despite the frequent impacts during running, researchers calculated that “the impact forces and stresses acting on cartilage, bones, ligaments, and tendons during running are typically within an acceptable range” (source). A large meta-analysis of studies of osteoarthritis in runners concluded that “long-distance running does not increase the risk of osteoarthritis of the knees and hips for healthy people” who do not have any preexisting medical conditions in the legs (source). One of the highest-quality studies in this analysis compared 504 varsity cross country runners to 284 varsity swimmers. The researchers wanted to know whether the runners had a higher prevalence of arthritis after 25 years. In the end, long-distance running was not associated with higher incidence of osteoarthritis of the hip or knee. In fact, long-distance running might even have a protective effect against joint degeneration, because it increases circulation through the joints and strengthens muscles that prevent joint stress.
Conclusion
This post is very insufficient. I just wanted to do some research and then collect it in a place where I can reference it later. I feel pretty okay with running now — especially trail running.