Maintaining healthy bones in both the short and long term is of crucial importance to runners. Bone stress injuries, also known as stress reactions and stress fractures, are one of the most frustrating and dreaded injuries for runners. They make up 15-20% of all running injuries per year, often appear without warning and can mean weeks or even months off from running. Ugh!
Bone Response to Loading
Bone is one of the most metabolically active tissues in the body with about 10% of bone normally being broken down and rebuilt at any point in time. Bone stress injuries result when repetitive stress on bone is too high and recovery is inadequate, causing bone breakdown to outpace the rate of repair. Tiny microfractures appear in the bone which then accumulate and coalesce into an area of injury. Training errors can contribute to this, but runners with less than optimal bone density are also more susceptible to injury.
But shouldn’t runners naturally have strong bones from all the running they do?
You can be forgiven if your initial answer was “yes”. For many years, weight-bearing exercises like running and walking were thought to be excellent ways to build and maintain strong bones. And these activities are still superior to non-weight-bearing exercises like swimming and cycling. Bone generally becomes stronger in areas where it is loaded, however recent research has shown that the type, speed and variability of loading matters a great deal as to how the bone responds. The repetitive loading of running and walking very quickly becomes boring to bone cells. Within a few minutes of starting your run, those bone building cells lose sensitivity to the mechanical stimuli and stop responding.
Building Stronger Bones through Physical Activity
So how can runners build stronger bones? Bones respond best to high loads that are unpredictable and come from multiple directions. Think of sports that involve changes in speed and direction and frequent accelerations and decelerations like basketball and soccer. One study found that female collegiate runners who played these sports growing up had leg and foot bones with around 10-20% greater area, volume and thickness than women who only ran. This increased bone size translated into an estimated 10-20% increase in bone strength.
The take home message here—do something other than run! And if you have kids who love to run, make sure they also play another sport. Join a pick-up basketball game at the gym, play pickleball or tennis, or chase your kids around the yard. The very rapid impacts of fast plyometrics like jumping rope can also build bone density. Strength training is beneficial because the muscle attachments pull on bones from a variety of different angles that running does not.
Building Stronger Bones through Nutrition
Runners can also build stronger bones by ensuring an adequate supply of nutritional building blocks. Most people can name calcium and vitamin D as elements of crucial importance, but eating enough total calories to support the demands of running is also critical.
Underfueling is more common than you might think—a recent study of Boston Marathon participants found that 42% of female and 18% of male runners reported low energy intakes relative to their usual activity levels and in many cases, this was unintentional—i.e., they were not trying to lose weight. Chronic underfueling can lead to a disorder called Relative Energy Deficiency in Sport (RED-S) in both men and women. The resulting negative consequences are not just limited to bone, but can also impair immune, cardiovascular, and reproductive function as well as impact mental health.
More recently, a reduction in carbohydrate intake has been associated with decreased bone formation and increased breakdown. Fueling with carbohydrates before and after a run is starting to look even more important!
How to Learn More
Want to learn more about building and keeping strong bones throughout your lifespan? Join us at the Motion Center as we discuss these topics in greater depth! You can attend in person or online on Tuesday, March 18, 2025, at 6:30 pm. This event is free and open to the public, but registration is requested in advance here. You can indicate that you would like to attend virtually and TCM will email you a link the morning of the program.
The information provided in this article and linked videos is intended for general education and demonstration purposes only. It does not substitute for professional medical advice. Consult a medical professional or healthcare provider if you seek medical advice, diagnosis, or treatment specific to your individual situation.
Kristen Gerlach, PT, PhD, is a physical therapist who specializes in working with runners. She is one of the team of Motion Experts TCM has gathered to help its subscribers and participants get the most out of their running. Have a question for Kristen: [email protected] or website: instridemnpt.com.