Are you a constant sufferer of stress related bone injuries? An endurance athlete? Female?
There are many different contributing factors of stress fractures in endurance athletes. Overcoming these challenges and working toward the prevention of these injuries is so important in order to continue with our training and competition schedule. In this article ,I will discuss why female endurance runners are more susceptible to these injuries along with some modifiable risk factors (i.e. nutrition interventions) that can be manipulated to reduce your risk of suffering one!
(Men, I did not forget about you. Stay tuned for an article on stress fractures in male endurance athletes!)
Possible Reasons for Stress Fractures
There are many endurance athlete-specific reasons why stress fractures may occur. One reason for this is the fact that distance running has a high metabolic demand. It costs a lot of energy to run fast for long periods of time and thus increases our need for a higher caloric intake. This can put us at risk if we are inadvertently under consuming calories. Inadequate food intake including both overall energy and micronutrient intake, can play a role in increasing our risk of fractures.
Excessive negative energy balance aside, runners seem to be especially at risk compared to other endurance athletes who also consume lots of calories. Although running does indeed increase bone mineral density (bone strength) with the proper balance of training and recovery, the repetitive nature of high-volume running often leads to the athletes not taking adequate rest days and/or programming in periodized reduced training weeks. This can lead to insufficient recovery and healing of the bone in between bouts of stress and therefore not enough time for the bone to adapt and become stronger. I would refer you to my colleagues, Dr. Sean and Kayla Ng, at the clinic to find out more about how to structure your training schedule.
On top of inadvertent negative energy balances and insufficient recovery, some endurance athletes neglect the inclusion of a strength program into their training schedule. Lifting will act as a stimulus to increase bone mineral density. Not only this, but strength training can also aid in enhancing hours muscles ability to direct forces optimally through bones (i.e. compressive vs. sheer forces). For more on this, again I would encourage you to discuss this with my colleagues Dr. Sean and Kayla Ng.
Another risk factor is related to how in some circles, runners are often pressured to fit into the very thin and light body category. First off, low BMI or low weight in itself can be correlated with low bone mineral density. In addition, if that low weight is combined with weight loss efforts and low energy intake, this can wreak havoc on your bone health due to hormonal changes (i.e. decreased estrogen production) and resulting menstrual dysfunction (which can act as an early sign that your are consuming insufficient calories).
BUT, all is not lost! There is a lot we can do to overcome our bone health challenges. Nutrition, for one, is an easily modifiable risk factor that can have positive outcomes for our bone health.
Nutrition & Bone Related Injuries
To put the need for proper nutrition in maintaining bone health in perspective, here are the results of 3 interesting and very applicable studies on the topic:
- Negative energy balance and estrogen: Low energy availability, which is the amount of energy left over after exercise for normal physiological function expressed in calories/kg fat free mass, decreases estrogen levels. This results in a 4x greater risk of bone injury compared to those who have adequate energy availability.
- Insufficient calcium: Low calcium intake (800mg) resulted in 6x more risk for bone injury compared to high calcium (1500mg).
- NFL players and Vitamin D: In NFL male players, players with 1+ fractures had higher rates of inadequate levels of circulating Vitamin D.
So, here’s what you can do:
- Make sure nutrition intake closely matches energy demand of sport & daily life.
- Consume enough bone building materials (i.e. calcium, vitamin D, and magnesium)
- Weight loss tactics should be introduced at appropriate times (likely in the low training/off season) to reduce risk of injury close to race season.
I hope these statistics and general tips reinforce how important nutrition planning is for endurance female athletes. If you still have questions or need guidance on planning for your race season, come visit me at the clinic! You can check out more about me on my profile HERE.
Tenforde AS et al., 2016. Association of the female athlete triad risk assessment stratification to the development of bone stress injuries in collegiate athletes. The American Journal od Sports Medicine 45(2), 302-310.
Heikura IA, Uuitalo ALT, Stellingwerff T, Bergland D, Mero AA, Burke LM. 2017. Low energy availability is difficult to assess but outcomes have a large impact on bone injury rates in elite distance athletes. International Journal of Sport Nutrition and Exercise Metabolism.
Barrack et al., 2014. Higher incidences of bone stress injuries with increasing female athlete triad-related risk factors. The American Journal of Sports Medicine. 42(4). 949-958.
Papageorgiu M, Dolan E, Elliot-Sale KJ, Sale C. 2018. Reduced energy availability: implications for bone health in physically active populations. Eur J Nutr. 57:847-859.
Maroon JC, Mathyssek CM, Bost JW, Amos A, Winkelman R, Yates AP, Duca MA, Norwig. 2015. Vitamin D profile in National Football League players.