Imagine two piers. Both are built using the same solid design and quality material. These piers are identical in every way, with one exception. Pier One is built over the ocean and is regularly subjected to storms and rough seas. Pier Two is erected over a small lake with calm waters. As years pass, Pier One takes regular beatings from high surf and gale force winds. Builders are constantly repairing and replacing its pillars and support beams. Pier Two, on the other hand, gets very little abuse in its placid environment and, on the surface, shows little need for repair.
Fast forward 50 years. Pier One sits majestically above the same rough seas and storms. With its pillars and support beams continuously replaced over the years, it still stands like a fortress. Pier Two, well, Pier Two collapsed some years ago. Its decaying pillars were never repaired or replaced and it eventually buckled mercilessly under the force of neglect.
Now imagine your bones as a Pier. If you are a runner, chances are your bones are like Pier One - constantly abused, but always being repaired and replaced. If you’re a cyclist, well, your bones might be like Pier Two, a shrine of tranquility but getting weaker beneath the surface.
This isn’t a joke guys and gals. According to Pam Hinton, PhD and associate professor of nutritional sciences at the University of Missouri, running promotes stronger bones, while cycling does the opposite.
Hinton co-authored a study this year comparing bone densities of elite runners to those of similarly accomplished cyclists. Her work was published in the journal Clinical and Experimental Metabolism. I recently caught up with Pam via email to learn more about her research on this topic and what it all means to runners and cyclists.
Will: Pam, first of all thank you for doing this interview.
PH: You’re welcome. Thank you for the opportunity to talk about our research and to increase awareness of this important problem that affects apparently healthy and fit individuals.
Will: I’ve read that you were a competitive runner in college, but a car accident ended your running career. You then became a cyclist. Can you talk a little about this experience? How does this motivate you and your research?
PH: Well, a great thing about my job is that I have the freedom to study problems that interest me—both professionally and personally. Some of the best career advice I ever received was from my postdoc mentor at Cornell University, Dr. Rasmussen. She told me that I SHOULD study what I am passionate about. She said that the odds of being a successful researcher are much greater if you’re passionate about your work. I’ve been interested in the interactive effects of nutrition and physical activity on bone for a long time.
Since my days as runner for the University of Wisconsin, I have been interested in how energy balance affects bone health. At that time, I was interested in how being in an energy-deprived state results in loss of bone mass, even if the skeleton is exposed to high-impact loading. As you mentioned, I was hit by a car and suffered a fracture that required surgery and almost a year of physical therapy. I took up cycling as a result. The inspiration to look at bone density in male cyclists hit me on a group ride one day.
We know that there are three key factors for maintenance of strong bones: adequate nutrition, especially calcium and vitamin D; normal hormonal status; and, regular loading of the skeleton. Although the men I ride with get enough dietary calcium and do not have endocrine issues, I wondered what years of spending so much time in a non-weight-bearing sport would do to their bones.
Will: I’ve always thought cycling was less damaging to your body than running. But your study on the bone densities of runners and cyclists would appear to indicate the opposite. Can you explain the results of your study?
PH: High impact (ground reaction) forces exerted on the skeleton during running or other high-impact physical activities are both good for the bones and bad for the joints (especially if your anatomy or biomechanics are not suited to running). What we found in our cross-sectional study is that cyclists had lower bone density of the lumbar spine than runners. In addition, ~65% of the cyclists we studied had osteopenia of the lumbar spine or hip. Osteopenia can be viewed as “pre-osteoporosis.”
The clinical definition of osteopenia is bone mineral density that is one standard deviation below the mean for young adults, while osteoporosis is less than 2.5 standard deviations below the mean. On a population level, fracture risk increased 2-3-fold for each standard deviation below the mean. So, it appears that the cyclists in our study were at increased risk for fracture of the lumbar spine.
Will: Can you tell us about the number and type of athletes that were involved in this study?
PH: We had 43 amateur runners and cyclists aged 20-59 years in the study. The athletes who participated in our study were competitive at the local and regional level.
Will: What kind of questions did you get from the athletes when they learned of the results? What kind of feedback did you give them?
PH: Most of the participants who learned that they had low bone density were surprised to learn that they had low bone density—typically a disease of older women! Their reaction was understandable, as these were otherwise very healthy and fit individuals. Some did not believe that the results were anything to worry about—“I’ve crashed many times and never broken anything!” However, the majority were concerned and wanted to know what they could do. We recommended that they contact their physician for follow-up treatment.
Will: I’ve known many runners who have had to hang it up because of various injuries. Doesn’t running pose other risks that aren’t present in cycling? How do runners avoid these debilitating injuries?
PH: Yes, although running-related injury is not my area of expertise, life-long runners often develop joint or soft-tissue problems that are associated with the repetitive impact of running. From a bone-strengthening perspective, however, it doesn’t take much running to achieve the maximal benefit. Unlike most benefits of exercise, more is not better when it comes to bone. This is because the bone becomes refractory after 100 loading cycles (i.e., impacts or foot strikes). Bone recovers after 8 hours of rest and will respond to additional loading. So, from a practical point of view, it makes the most sense to do more short bouts of high-impact activity as opposed to longer bouts less frequently.
Will: Do swimmers have the same risk as cyclist when it comes to bone strength?
PH: We have not studied swimmers, but, yes, we suspect that swimmers would be at increased risk. Swimming, like cycling, does not produce ground reaction forces on the skeleton.
Will: At what age should someone be worried about osteopenia?
PH: The key to prevention of osteopenia or osteoporosis is maximizing peak bone mass during periods of skeletal growth. A normal consequence of aging is loss of bone mass. Thus, the goal during childhood, adolescence, and young adulthood is to put as much bone in the bank, so to speak, as possible to minimize the negative consequences of age-related loss. However, unless an individual is at risk, e.g., use of medications that cause bone loss, endocrine disorders, or decreased estrogen, clinically significant bone loss does not typically emerge until after menopause in women and age 70 in men.
Will: How can one find out if they suffer from or are at risk of osteopenia?
PH: They must have their bone density measured. The most accurate assessment is measurement by dual-energy X-ray absorptiometry (DXA).
Will: Can supplements help minimize risk of osteopenia?
PH: Adequate nutrition, especially calcium and vitamin D, but other nutrients, too, is necessary but not sufficient. In other words, supplemental calcium cannot “make-up” for lack of weight-bearing activity or inadequate estrogen.
Will: What can we expect to see from you next? Are you planning any future studies?
PH: Just last month, we were awarded a 3-year grant from the National Institutes of Health to determine the efficacy of one-year exercise-based intervention to increase bone mass in men with osteopenia. We are going to compare plyometrics (jump-training) and resistance exercise.
Will: Thank you Pam. Your work is very enlightening. I look forward to hearing more about your next project!