April 3, 2011
Written by: Dr David Ness, CCSP, ART, CGFI
Stress fractures, also known as fatigue or hairline fractures, are caused by repeated stress or heavy, continuous weight. They are much more likely to occur in the lower extremities, which bear the body’s weight, than in the upper. A sudden increase in physical activity, such as rapidly ramping up training for a big event, is often the underlying cause. Bones attempt to remodel and repair themselves, but can be overwhelmed if the amount of stress increases suddenly and is maintained at that higher level of intensity. The osteoblasts, the cells which are responsible for bone growth and repair, simply can’t keep up with the extra work, and a stress fracture forms.
Muscle fatigue can also contribute to stress fractures, particularly in the lower leg. Muscles and bones both absorb the impacts of running, serving as shock absorbers for the body. As fatigue sets in, the bones must shoulder a greater part of the stress, increasing their vulnerability to fracturing.
Symptoms and treatment
Stress fractures present themselves as a generalized area of pain around the affected area, which is aggravated by weight-bearing activities. A runner may find the pain to be most severe at the beginning and end of the run. Stress fractures are often invisible to X-rays, so an MRI or CT scan may be necessary for a clear diagnosis.
Runners can easily misdiagnose the pain from a stress fracture as being caused by shin splints, a less serious condition which affects the connective tissue. In shin splints, the pain is found along the length of the tibia, while the pain of a stress fracture is more localized.
The most effective treatment for a stress fracture is rest, which includes avoiding putting weight on the injured extremity. Completely avoiding training may be necessary to allow the healing process to continue, as it takes little effort to undue the body’s repairs to the broken bone. Use of a cast or boot, ice, and crutches may also be necessary during the healing period, which can take from four weeks to several months. Surgery, including pinning, may be needed in severe cases. Even after the fracture is healed, the risk of refracturing is heightened for months to come.
While a sudden increase in training can increase the risk of stress fractures, more moderate increases to the schedule can have the opposite effect. Muscles and bones alike can be strengthened through a good training regimen, such as following the runner’s axiom of limiting distance increases to ten percent per week. This will allow the body to compensate for the additional stresses, rather than succumbing to them. In addition strength training, particularly of the legs, will allow the muscles to more effectively reduce the amount of stress which is put upon the bones themselves.
Both calcium and vitamin D play important roles in bone density and strength, and most athletes do not replenish them fast enough to do the most good. Bone Mineral Density (BMD) is a significant factor in determining the risk of stress fractures. BMD is lower in Caucasians, women, and highly active athletes.
New research suggests that athletes may need to take as much as 2,000 mg of calcium daily to increase BMD, simply due to the amount which is lost in sweat alone. In a study of female Navy recruits, incidences of stress fractures dropped 21% among those taking this amount of calcium. The study participants were also given supplemental vitamin D, which helps the body absorb calcium.
Vitamin D can be manufactured by the body given enough sunlight, but increased use of sunscreen and indoor training makes it difficult to make enough for an athlete’s needs. Inadequate vitamin D levels have been linked to increased stress fractures as well as inferior muscle strength, musculoskeletal pain, and a host of other problems.
Both vitamin D and calcium can be taken in food or via supplements.
Dr. David Ness is a certified sports chiropractor, practicing in New Paltz. He has worked the last 4 years at the Lake Placid Iron man event as part of the ART treatment team. As well, Dr. Ness has been the ART provider for the HVTC for the past three years providing free ART care after club races. Dr. Ness also provides treatment at NYTC races around the NY metro area, and continues to work as part of the SOS Triathlon post-race care team. Dr. Ness can be reached at (845) 255-1200.