Disclaimer: I am an avid runner and I admit to cherry-picking scientific research to advance the argument that running is AWESOME :).
I recently read a really interesting article by Gretchen Reynolds that shared new research findings regarding the benefits of running. I have summarized the article below:
I have a lot of patients who come to me with the worry that running ruins knees and is dangerous. They question whether they should continue down the destructive path or transition to something lower impact and safer like the elliptical trainer.
I am happy to report that a new study finds that running may actually benefit the knee, improving the biochemical environment inside the knee to keep things working (running :)) smoothly.
A popular argument is that running is dangerous to knees: the cumulative effects of impact on the knee from running inevitably results in slow wear and tear of the cartilage cushion of the knee, resulting in damage to the joint resulting in arthritis.
Thankfully, there is little evidence to support this argument and a growing body of evidence argues the contrary: epidemiological studies of long-term runners show that they are less likely to develop knee osteoarthritis than people who don't run.
Scientists posit that running may protect the knee because running is associated with relatively low body mass and carrying less body mass is known to reduce the risk of knee osteoarthritis. Some researchers question whether running may have a more directly positive impact on knee joints, perhaps by impacting the workings of various cells within the knee.
Researchers at Brigham Young University sought to find out the answer by recruiting 15 female and male runners under 30 years old without a history of knee injury or arthritis. The goal was to study people with healthy knees in order to better isolate running's impact on otherwise normal joints. The volunteers had blood drawn from an arm and then had a small amount of fluid (termed "synovial fluid") removed from their right knee. This fluid is a naturally-occurring fluid within joints that reduces friction through lubrication. Healthy knees contain only a small amount but arthritic or otherwise unhealthy knees contain much greater quantities of synovial fluid.
Next, the volunteers were transported via wheelchair to the university biomechanics lab where they either sat quietly for 30 minutes or ran on a treadmill at their preferred running speed for 30 minutes. Following their respective 30 minutes of sitting or running, they were again wheeled to the clinic where blood and synovial fluid draws were again performed. Each volunteer completed both a sitting and a running session on separate days.
Once the blood and synovial fluid draws were complete, the researchers investigated a variety of substances within the young runners' blood and synovial fluid. They focused particularly on molecules associated with inflammation because low-grade inflammation has been associated with the development and progression of arthritis.
The researchers looked for changes in the levels of several types of cells that are known to either increase or diminish the amount of inflammation within the knee. They also looked for changes in the level of a substance known as cartilage oligomeric matrix protein (COMP) which is often used as a marker of incipient or worsening arthritis. Compared to healthy knees, knees with arthritis can have about five times as much COMP in their synovial fluid.
Unfortunately, it turned out to be technically difficult to safely extract much synovial fluid from these healthy knees and the scientists wound up with complete numbers in only six out of the thirty runners.
But that being said, the data were interesting and consistent. In nearly every case, the runners' knee showed substantially lower levels of two types of cells that contribute to synovial inflammation, compared to their baseline levels. The runners showed a shift in their COMP: they had more of the substance in their blood and less in their synovial fluid. It seemed that running had squeezed the inflammatory substance out of their knee and instead into the blood.
Meanwhile, sitting resulted in slightly increased levels of COMP inside the knee and also raised the concentration of one of the inflammatory molecules.
Overall, these findings indicate that a single 30-minute session of running changes the interior environment of the knee, reducing inflammation and diminishing the level of a marker of arthritis.
An unexpected finding of the study is that sitting for 3o minutes also changes the interior environment of the knee, a finding that the authors of the study had not expected. Sitting seems to make the knee more biochemically vulnerable to later disease.
The lead author, Dr. Robert Hyldahl, professor of exercise science at BYU, notes that this study is very small and short-term. He would prefer to repeat it on a much larger scale "once we figure out how to get more synovial fluid" safely from healthy knees.
Dr. Hyldahl and his colleagues also hope to study longer running distances and various paces to see how these variables affect change within the knee. They also hope to recruit older and injured runners whose knees might have begun to respond fundamentally differently to the act of running than the joints of healthy people in their 20s.
Despite the limitations of the study, the lead author notes that the findings argue that moderate amounts of running are not likely to harm healthy knees and likely offer protection against joint damage.
I want to share a terrific article explaining the benefit of high-impact exercise. I have had countless patients ask me if it is best to continue running and participating in other high-impact exercises or if it would be better to cut back and strictly embrace more gentle types of exercise; this article certainly makes a case for the former and I talk with my patients frequently about its findings and recommendations.
This article by Gretchen Reynolds provides a compelling argument as to why we should continually participate in exercises that jar our bodies. I've summarized its content below.
A study by researchers at the University of Bristol found that athletes who experienced impacts of 4.2 G's or greater had significantly sturdier hipbones than athletes who did not participate in exercises that reached that threshold. Exercises that generate enough force to achieve 4.2 G's include running a 10-minute mile or jumping up onto and off of a box that is 15 inches or higher. This study compels me to encourage all of my patients, especially my patients who are in their forties, fifties, and beyond, to pound the ground in order to strengthen their bones and (hopefully) prevent fragility fractures such as hip fractures.
Another study found that after four months of high-impact jump training (simply hopping in place), hip bone mineral density (BMD) could be improved in premenopausal women by jumping 10 or 20 times, twice daily, with 30 seconds of rest between each jump. This is exciting news for anyone looking to optimize their bone health and prevent injury organically through exercise.
As always, it is best to consult your physician before initiating a new exercise program and certainly this is the case with older individuals seeking to start a high-impact exercise program as the stress required to improve bone health may be too much for certain individuals' bodies and bones to handle, at least initially. This caveat also applies to those of us with joint troubles including arthritis.
Up until today, I didn't give much consideration to how I, as an orthopaedic surgeon, could contribute to the discussion of how much is safe with regards to safe quantities of alcohol consumption. The op-ed piece entitled "Drinking by Numbers," by Bonnie Tsui, published today in the New York Times Sunday Review section, changed that.
I found Ms. Tsui's article to be incredibly insightful and thought-provoking and it immediately sparked me to examine my clinical practice and how I counsel my patients with regards to alcohol consumption. As an orthopaedic surgeon, I have an inherent vested interest in my patients' bone health and I frequently advise my patients to engage in weekly or biweekly impact exercise to maximize bone density and strength (for an excellent general article on the topic of the importance of high-impact exercise, click here). Counseling regarding alcohol consumption is relevant in my practice because alcohol can (and frequently does) lead to impaired balance, compromised decision-making, and incredibly entertaining but risky dance moves, among other things. These, in turn, lead to orthopaedic injuries such as shoulder fractures and broken hips. Instead of yet another scientific article that merely facilitates further confusion as to whether or not alcohol consumption is healthy or unhealthy, Ms. Tsui's nuanced article examines the motivations behind alcohol consumption and provides an extremely useful suggestion as to how one can determine a safe number of alcoholic beverages to consume:
"Nothing is as important as something. Nothing is the reference point from which we can judge all else. The numerical middle is different for everyone, but perhaps that’s the point. Because my number is two and yours may be one and his might be five, the most relevant number to us all is zero.Maybe the only way to think about drinking by numbers is not to obsess over how much is too much, but to be acquainted with what zero feels like — that is, to come back to zero often enough to understand the relative value of our numbers. The reset helps us see those numbers for what they are."
This advice recognizes that everyone's tolerance is different and does not attempt to give a hard and fast number for a "safe" quantity of alcohol. Instead, it advocates awareness and thoughtfulness, as well as moderation. I wholeheartedly agree.
Sara Jurek, MD