When we stop growing, our bones don’t; they are a constantly evolving tissue. Just as it is for muscles, this process is modulated by the volume and intensity of the loading a bone experiences – physical stress stimulates bone renewal and maximisation of bone density, while a reduction in loading will cause the bone resorption. Some bone resorption occurs naturally with age, but accelerated bone resorption is pathological, known as osteoporosis.
A stress fracture is a break in a bone which has been caused by excessive, repetitive forces. Stress fractures are most likely to occur in athletes experiencing a sudden increase in training volume or intensity as the rate of “reinforcement” of the bone cannot keep pace with the increased loading. Consequently the bone cannot resist the loading it is placed under and small stress fractures or breaks appear.
Stress fractures are more likely to occur when an athlete has a poor biomechanical profile. Poor movement patterns associated with stiff joints, tight or weak muscles, stiff nerves or bad habits are likely to cause forces to be unevenly distributed causing increased localised bone stress and the potential for a bony stress reaction. Physiotherapists can address these potential precursors to stress fractures, not only reducing the risk of injury but also optimising performance.
Nutritional deficits such as inadequate intake of calcium, vitamin D, phosphorous, potassium, vitamin C, fibre, protein, fat, and iron can increase the risk of a stress fracture occurring, as these nutrients are essential for optimising bone density in response to training. A low body mass index (BMI) indicating a low weight relative to height is also associated with an increased risk of stress fracture.
In runners, stress fractures most commonly occur in the foot, shin, hip or pelvis. In rowers, rib stress fractures are most common whilst in football, pelvic and shin stress fractures have the highest prevalence.
For stress fractures of the foot and shin, footwear that has inadequate cushioning or support can also be a contributor. Podiatrists can assist in recommending appropriate footwear choices as well as assessing suitability for an orthotic device to help optimise technique and performance.
Female athletes should also be aware that menstrual dysfunction (either cessation or irregular menstruation) can increase the risk of stress fractures as the hormones which regulate the menstrual cycle are also involved in balancing the process of resorption and renewal of bone cells.
Unfortunately, once a stress fracture has occurred, the most likely treatment is rest. So, could that niggling foot pain, sore shin or hip/groin pain be a stress fracture? Minimise your risk factors and get it checked… prevention is best.