Running sounds like a healthy activity and in general anything that makes you move and keeps you active is good for your health overall when compared to living a sedentary lifestyle, however, too much running may lead to injury. 

Excessive vigorous exercise is not good for your health and researchers are still trying to figure out what the safe limits are. It turns out that people who work out at higher intensities for too long may be in fact, less healthy than their more sedentary peers.  It has also been found that people who work out too hard and for too long may be more likely to die than those that participate in more moderate exercise.  

Numerous studies have demonstrated that moderate exercise is (very) good for you but excessive exercise can be damaging.  In one study published in the European Heart Journal, researchers looked at the hearts of a 108 chronic marathoners and sedentary people and it was found that the runners had more coronary plaque buildup, which is a risk factor for cardiovascular disease. It has also been found that the health benefits may diminish when you get into the higher intensity and higher duration of exercise and that it may be more beneficial to exercise at a moderate rate for a moderate amount of time. 

Excessive exercise can cause significant wear and tear on your body.  When you exercise you create oxidative stress on your body. Oxidative stress is defined as essentially an imbalance between the production of free radicals and the ability of the body to counteract or detoxify their harmful effects through neutralization by antioxidants. During a high intensity workout, your body has to work hard to burn sugar and fat to gain fuel.  Your body creates free radicals during this process that can bind with cholesterol to create plaque buildup in your arteries which then damage your cells.  If you work at a more moderate pace (or duration) the body doesn’t need to work as hard to gain fuel to keep you going and therefore is thought to have less oxidative stress.  

Related: What you can do NOW to prevent knee problems in the future

According to James O’Keefe, MD prolonged intense exercise causes excessive oxidative stress which can burn through antioxidants in your system and pre-dispose you to problems. An article by Dr. O’keefe highlighted the risks of excessive endurance training. Dr. O’keefe reported that chronic intense and sustained exercise can cause a variety of heart problems including atrial and ventricular arrhythmias.  There was found to be a 5-fold increase in the prevalence of atrial fibrillation in veteran endurance athletes in sports such as marathon or ultramarathon running or professional cycling.  It was also found that intense endurance exercise efforts often cause elevation in biomarkers for myocardial injury.  

(Related, but a more personal note: My experience with excessive overtraining)

Another common problem with runners are musculoskeletal injuries. It has been estimated that 27% to 70% of runners sustain some type of injury at one point. Highly repetitive, impactful, weight-bearing that occurs with running can cause overuse type injuries. These injuries generally occur when a structure is exposed to a large number of repetitive forces at the knee, lower leg or foot.  Inadequate recovery time between training sessions in people who participate in excessive running can also result in an overuse injury.  Repeated applied stresses that are below the tensile limit of a structure lead to positive remodeling if sufficient rest time is provided between the stressful activities.  Just another reason why rest is so important. 

It may be beneficial to reduce running duration and frequency in order to decrease impact forces through the lower extremity and help to decrease the risk of injury. Longer rest periods should be encouraged in order to allow healing or remodeling of the tissue to occur between sessions.   Proximal core hip strength is also needed to control the distal segments to help to prevent injuries. If one joint of the lower extremity is not functioning correctly, injuries can occur at other joints and structures.  Hip weakness may play a role in knee and ankle overuse injuries and it is important to add strengthening exercises to specifically target weak hip muscles to offer better results in people with running injuries.   

Written by L Augustyn, PT

*Always talk to your personal health care physician before starting into any exercise training program.

FB Note: We believe that if something gets you moving and makes you feel great, you should embrace it. However, as you've likely heard us repeat like broken records, we also believe you need to listen to your body, practice moderate/balanced training duration and intensities, varied training types (i.e. you don't want a program that involves only running), and of course, allow your body a proper chance to heal itself between intense training sessions. You could probably turn almost any kind of training into a health detriment if you did it without proper rest, and with reckless abandon. This article is in no way trying to knock running or the people who love it; it's merely a reminder to stay aware of the way your training is balanced and to practice caution and moderation - and to fully embrace rest. We have a lot of people in our audience who love marathons and long distance cycling and the like. What we've found is that once they diversify their training program with other training types (diverse from what they're actually training for), they've seen their performance times improve drastically, and their injuries tend to either subside, or they find that they're encountering less new ones. We offer a 8 Week Cross Training Program that has 3 varied workouts a week - including strength, stretching & high intensity interval training - with muscular balance and range of motion in mind, for while you're training in a more direct, less varied way (i.e. running, swimming, cycling, hiking, etc). 

On a more anecdotal note, I had really awful knee and back pain from the time I was 14 - 14! can you believe that!? - until I was about 24 years old. During a lot of that time, I ran for at least an hour 5-6 days a week. I was over training and not training smart - running was almost all I did. In the last decade, since I started training the way we share with you guys here onsite, I have had almost no back pain whatsoever while in my late twenties and now mid thirties. Just thought I'd throw my experience in there; over training is surprisingly easy to do and a lot of us are guilty of it. 

Long story short, stay tuned in to the signals that your body is sending you, and realize that more is not always better - not when it comes to looking fit, feeling fit, performing better, or health. Moderation is a beautiful thing, and we believe that it contributes to longevity in life and in being able to sustain your exercise program, whatever it may be. 

We want to hear from you: Do you guys include running in your training program? How often, and how far? Do you run on a treadmill or outdoors? Do you compete? We'd love to hear about your experience and approach! 

References
Hreljac A. Impact and overuse injuries in runners. Med. Sci. Sports Exerc. 2004; 36(5):845-849. 
Niemuth PE, Johnson RJ, Myeres MJ, Thieman TJ. Hip muscle weakness and overuse injuries in recreational runners. Clin J Sports Med. 2005; 15:14-21. 
O’Keefe J, et al. Potential adverse cardiovascular effects from excessive endurance exercise. Mayo Clin Proc. 2012; 87 (6): 587-595. 
http://www.active.com/health/articles/why-too-much-running-is-bad-for-your-health
www.news-medical.net/health/What-is-Oxidative-Stress.aspx