As running become more popular as a form of exercise, the risk for developing musculoskeletal injuries goes up as well. Stress fractures are one of the most serious injuries, it account for 6-20% of injuries in track and field athletes and long distance runners (4) . In runners, stress fracture are most commonly seen in the tibia, which requires an average of 8 weeks of recovery (2). The focus of the post will be in educating you on what stress fractures are, the risk factors, and preventative suggestions.
What's a Stress Fracture?
Before we go into details about stress fractures, lets talk about something we all learned in High school, Wolff’s Law. Wolff’s law was developed by a German surgeon that states “bone in a healthy person or animal will adapt to the loads under which it is placed. If loading on a particular bone increases, the bone will remodel itself over time to become stronger to resist that sort of loading. The internal architecture of the trabecular undergoes adaptive changes, followed by secondary changes to the external cortical portion of the bone.”Therefore, if the stress occurs too fast without recovery, athletes develop microfractures.
Most stress fractures occur in the cortical bone (1). Cortical bone is located “in the diaphysis of long bones and the shell of square bones.
Stress fractures are tiny microfractures of the bone and with running tend to occur from repetitive stress. There are 2 types of fractures, fatigue fracture and insufficiency fractures. Fatigue fractures are stress fractures that affect the cortical bone due to over-stress (2). Insufficiency fractures are caused by low bone mineral density (seen in anorexic runners, runners with osteoporosis, osteopenia). With proper recovery time, the bone damage is repaired.
HOWEVER, the problem develops when an athlete maintains an excessive running volume and inadequate recovery time because this can lead to BONE WEAKNESS and STRESS FRACTURES. Stress fractures tend to occur in the first month of training or when training is increased too quickly.
Risk Factors for Developing Stress Fractures:
Definitely describing the factors that lead to stress fracture can be difficult because there are an array of variables that play into the problem . There are many intrinsic and extrinsic factors that lead to stress fractures.
Intrinsic factors:
1. Increase in impact forces: research has shown that athletes who demonstrate increase vertical load sustain stress fractures more so to runner that do not demonstrates that. So the next question becomes, how to runners average higher vertical loads vs lower vertical loads? That answer is: fatigue. At the end of fatiguing runs, ground reaction forces (GRF) as observed to be greater in those runners with a history of stress fractures. It is noted that muscle fatigue alters running biomechanics which is associated with a 25% increase in GFR (2).
2. Poor strength : This plays off the previous factor. Decrease strength as well and endurance of the muscle that support the hips and lower extremities such as the glutes, gastocs, and ankle stabilizers (peroneal, posterior tib) all contribute to balance and power us through our work outs. There will be imbalances and strength discrepancies and all that leads to is compensation and injury. I have said this hundreds of times and I will say it again, YOU NEED TO BE STRONG IN ORDER TO RUN. Strength training is crucial!
Pronation is NORMAL- however not coming out of pronation, or too much of it is problematic
3. Excessive hip adduction and rear-foot eversion: faulty running mechanics means, decrease shock absorption or excessive force in certain joints of the body. Too much hip adduction (leg landing towards midline versus under hip) causes increase stresses at the knee and lead for the foot to compensate by landing on the outside of the heel leading to increase pronation arc and therefore creating more stress at the ankle joint.
Extrinsic Factors:
1. Increase in frequency, duration, or intensity when the athlete is not ready: this tends to be a very common trend in more athletes who suffer from stress fracture. Somewhere in training things progressed too fast.
2. Running on harder surfaces vs soft – studies have shown that running on the treadmill decrease GRF versus concrete.
3. Failure to schedule rest days after higher intensity runs : REST DAYS ARE NEEDED. It is really easy for runners to get caught up in training and the desire to progress. However, the body needs to recover and heal. Overtraining without breaks leads to opposite of what athlete want, and that breakdown, injuries, and decrease performance.
4. Poor periodization training: Proper periodization blocks of 4-6 weeks of progressive base building and progression of 10% of miles per week is overlooked or ignored by many. Set a plan, follow the plan, and don’t get too excited.
5. Training in old shoes: some studies have looked at show breakdown, many coaches and companies say max of 300 milers her shoe. However that can vary depending on your weight, miles per day etc. I say if the shoe doesn’t feel supportive, there is wear and tear of the sole, get new shoes. Another good recommendation is have a difference pair of shoes for cross training, speed workouts, and long distance runs.
Signs and Symptoms:
1. Insidious onset of pain that develops towards the end of a run, that then progresses to pain early on with running is the athlete continued to train.
2. If the fracture advances, the athlete will feel pain even with non running related activities and will have pain with regular ambulation/walking.
3. Focal bony tenderness or sharpness with weight bearing and swelling, will feel like really bad shin splints.
4. Sometimes: discoloration/bruising.
Some questions to ask yourself if you believe you may have a stress fracture and need to get checked out.
a. Has your training changed? If so, how much have you increased your miles per week, or have you increased your pace? and if so by what?
b. Are you waking up with more aches?
c. Are you taking rest days?
d. Have you changed your shoes, or started running in new shoes?
e. Is the pain getting worse?
f. Does walking produce your pain?
g. Is the pain limiting your ability to train?
If yes >4 , go to the doctors, or get checked my a physical therapist. Stress fractures can present as shin splints, or tendonitis. Only way to verify a fracture is through imaging, and even then they sometimes will not show up on X-ray until 1-2 weeks later.
Lift some iron!!!
Prevention Interventions:
1. Strength Training: ALL runners and athletes greatly benefit from increases in strength. For runners specifically they need hypertrophy, and muscle endurance. 2-3x per week with increases in load up to 75-95% of 1RM. Progression should be made in 3x3 week periodization blocks. If you are not sure what that means, start by lifting some light weights and slowly progress and get yourself a trainer. Incorporate loaded squats, lunges, step ups, core and glute exercises.
2. Do not increase miles by more than 10%. Increase 10% for 3 weeks and on the fourth week should be an easy week, and resume back to training. For beginners, running 3x a weeks is good, intermediate and elite runners need to play close attention to aches and pains post hard work outs and take days off seriously.
3. Own more than 1 pair of shoes. You should have a pair for cross training, speed days, and distance running.
4. TAKE 1 REST DAY A WEEK: that means very light 30 min or less JOG, walk, or so nothing and stretch.
LISTEN TO YOUR BODY.
TRAINING SMART, will allow your run better, faster, stronger, and injury free
- JESSICA MENA PT, DPT, CSCS
and fellow runner.
References
1. Harrast MA, Colonno D. Stress Fractures in Runners. Clinical Sports Medicine 2010. 29. p399-416. doi:10.1016/j.csm.2010.03.001
2. Magness S, Ambegankar JP, Jones MT, Caswell D. Lower Extremity Stress Fractures in Runners: Risk Factors and Prevention. Injury Prevention & Performance Enhancement- Human Kinetics. 2011. Pp 11-15
3. Magrum E, Wilder RP. Evaluation of Injured Runner. Clinical Sports Medicine. 2010 p 331-345. Doi: 10.1016/j/.csm.2010.03.009
4. Meardon SA, Willson JD, Gries SR, Kernozek TW, Derrick TR. Bone stress in runners with tibial stress fracture. Clinical Biomechanics. 2015
5. Nicola T, Jewison D. The Anatomy and Biomechanics of Running. Clinical Sports Medicine. 2012. 187–201 doi:10.1016/j.csm.2011.10.001