Stress Fractures and Bone Stress Injuries are one of the most common injuries seen in runners. A bone stress injury is the inability of bone to withstand repetitive loading. This results in structural fatigue and localised bone pain/tenderness. Bone stress injuries exist on a continuum and if not managed early will lead to a stress fracture.
Bone is living structure, constantly remodelling itself based on what loads we apply to it. When we experience a bone stress injury, it is due to a disparity between the bones ability to rebuild itself and the breakdown of bone due to load.
Below we discuss how to reduce your risk of bone stress injuries. However, if you think you might have a bone stress injury, head to our article on recognising and treating bone stress injuries and stress fractures.
Preventing Bone Stress Injuries and Stress Fractures
It is impossible to 100% prevent bone stress injuries and stress fractures in runners, however, we can reduce the risk but addressing the risk factors. Let’s run through the main risk factors below.
Training Factors
The biggest risk factor for bone stress injuries is high training loads. This is the cumulative load from total milage, workout intensity and loading magnitude (hills, flat runner, running surface, step rate). We commonly see bone stress injuries when one or more of these factors is increased suddenly and is significantly higher than the individuals normal running loads. However, not all running loads are equal. We know that suddenly increasing speed work has the highest risk of resulting in a bone stress injury. This is because higher intensity running increases peak bone loads significantly more than slower, easy running.
When bone stress injuries occur due to changes in training load, it is not usually due to yesterdays run. Bone is slow to respond and if you start to experience localised bone pain or tenderness, look at your training load from 3-4 weeks ago.
Reducing Risk From Training Factors
- Increase training load slowly and consistently. No sudden increases in training because “you’re feeling good”.
- Increase running milage before increasing intensity. Once you are reaching your weekly milage goal, start adding in higher intensity work and drop your total milage slightly.
- Increase one aspect of training at a time. Don’t add higher milage, speed workouts and hill reps all at once.
Dietary Factors and Stress Fractures
Diet plays a major role in bone stress injuries and stress fractures and is is often overlooked by health professionals. Overall energy availability is a key factor affecting risk of bone stress injury. We go into this more in our article on RED-S. In essence, an athlete has low energy availability if their energy intake does not meet their daily energy demands. If this occurs for an extended period of time, bone is unable to respond to the loads of running and is unable to repair micro-damage, resulting in bone stress injuries.
The other key dietary factors are Calcium and Vitamin D status. These nutrients are key building blocks for bone repair. If an athlete has chronically low levels of Calcium or Vitamin D then risk of Bone Stress Injuries increases. Athletes on a vegan diet need to be aware of their calcium levels, whilst athletes who spend less time outdoors should be aware of their Vitamin D levels.
A study by Nieves et al. (2010) found that female distance runners who consumed less than 800 mg of calcium per day had nearly 6 times the bone stress injury rate of those who consumed more than 1500 mg.
Muscle Factors and Stress Fractures
Human bodies have two main systems that absorb load when running. Our skeletal system and our muscular system. The more load our skeletal system has to handle during running, the higher our risk of bone stress injury. The best way to attenuate skeletal load absorption is via our muscular system, which acts as a shock absorber. When our muscles are weakened, fatigued or display altered activity patterns, their ability to absorb load is compromised. This increases risk of bone stress injuries and stress fractures. Greater muscle size and strength are potentially protective against bone stress injury and stress fractures. This is one of the many benefits of regular strength training for runners.
In short, runners who regularly strength train have reduced risk of bone stress injuries and stress fractures.
Running Surface and Stress Fractures
Basically we don’t know if any particular running surface increases risk of bone stress injuries or stress fractures. However, we know that mixing up the running surface will alter the loads on your bone. Bone’s like different stimulus. If you regularly run on the road, find a trail and vice/versa. The science of this is complicated. Basically, different running surfaces will change peak bone loads, ground reaction force and tissue vibration.
Recognising When You Have A Bone Stress Injury
Bones stress injuries (BSI) and stress fractures are either high or low risk. High risk BSI’s are more likely to lead to a full fracture and take longer to heal. Low risk BSI’s can be managed more easily by reducing running load and undertaking specific strength exercises.
High risk bone stress injuries include:
- Navicular (bone along arch of foot)
- Femoral neck
- Front of the shin bone (anterior cortex of tibia)
Low risk bone stress injury sites include:
- Fibula
- Calcaneus (heel bone)
- Metatarsal shafts
A registered health professional is required to diagnose a bone stress injury. However, some key symptoms to look for are:
- Mild, diffuse ache around a specific areas
- Boney tenderness when you press on the bone
- Night pain
- Early morning pain
- Pain that does not go away after warming up and tends to continue until you stop running
Management of bone stress injuries and stress fractures
In the early stages of Bone Stress Injury a full stress fracture can be avoided, only if we listen to our body. When pain symptoms first present themselves, we must heed the warning. If we push through the pain of a bone stress injury, a stress fracture and a long road to recovery are inevitable.
When symptoms first present, you need to see your physiotherapist or local doctor. If a bone stress injury or stress fracture is suspected, an MRI or bone scan and CT are gold standard to confirm or deny this. Your doctor will likely suggest an X-Ray, however they cannot pick up bone stress injuries and will only pick up a significant stress fracture.
Management of a low risk bone stress injury can include reducing running load, improving diet and completing specific progressive strength exercises. Managing a high risk bone stress injury looks very similar but you will likely require an extended period with no running and may require to be non-weight bearing for stress fractures of some bones including the navicular.
If you suspect a bone stress injury or stress fracture, see your physiotherapist and/or local doctor immediately.
References
Nieves, J. W., Melsop, K., Curtis, M., Kelsey, J. L., Bachrach, L. K., Greendale, G., … & Sainani, K. L. (2010). Nutritional factors that influence change in bone density and stress fracture risk among young female cross-country runners. PM&R, 2(8), 740-750.
Warden, S. J., Davis, I. S., & Fredericson, M. (2014). Management and prevention of bone stress injuries in long-distance runners. journal of orthopaedic & sports physical therapy, 44(10), 749-765.