It’s common knowledge that endurance sports, specifically distance running, are not easy on the skeleton. As renowned bone stress injury expert Professor Stuart Warden put it, ‘not all athletes have good skeletons and distance running does not build good bones’! Beyond taking time off to enable the body to heal, there are few actions, such as increasing hydration, coaches can encourage so as to promote better bone health in their athletes. But first, let’s explore the common types of bone stress and how they occur.
Why Bone Stress Injuries Happen
Bone stress injuries are thought to occur at a rate of roughly twenty percent per year in runners and are usually caused by some kind of loading error. There are a number of risk factors with respect to bone injuries including diet, sex, changes to training volume and intensity and bone stress injury history. Unfortunately, once an athlete suffers from one injury they are likely to experience another.
Bone stress injuries come in a wide range — from moderately symptomatic shin splints, (or medial tibial stress syndrome) to a substantial and painful stress fracture.
If you could see through the human body and just look at the bones of a runner, (or anyone, for that matter) you would see a large number of microcracks. These microcracks would all have different ages and are considered perfectly healthy. Each run causes a bit of damage to our bones, but generally, this damage is repaired by the body. The repair time varies based on severity, with complete mineralization taking up to a year.
Bone Health and Hydration
A number of factors can promote good bone health. These include plyometric exercises, sleep optimization, strategic recovery as well as maintaining a well-rounded diet. But one often overlooked essential factor is hydration.
Despite a lack of abundant studies addressing bone stress injuries and hydration, there are a few pieces of evidence that offer valuable insight into bone health and hydration strategies for athletes.
One paper, published in the Journal of Sports Sciences, studied the impact of weight control practices on the bone health of jockeys. This study found that roughly half of the jockeys in the sample suffered from osteopenia (low bone density). The jockeys were also found to be chronically dehydrated. As such, there appears to be a correlation between low bone density and dehydration but there are a few contingencies to note.
Firstly, correlation is not causation — it is unlikely that dehydration was the sole cause of low bone density amongst these jockeys. However, it could be a contributing factor alongside unhealthy dieting and resulting chronic energy deficit, which commonly result in reduced bone density. Also, it’s important to note that jockey training is very different from that of runners so we can’t draw conclusions across sport types effectively.
Another study, published in the British Journal of Sports Medicine, entitled, ‘Nutrition and hydration concerns of the female football (soccer) player’ found similar results despite considering the different sport type. The athletes under study were chronically under-eating and underhydrating. As a result, the study concluded that ‘that dehydration adversely affects skill’.
Running is not as technical as football, but we know that a breakdown of form can cause overstriding, which qualifies as a loading error. This makes a bone stress injury more likely. As such, it’s reasonable to conclude that one can reduce their likelihood of incurring a bone stress injury by training in a well-hydrated state.
If you’re considering asking your athlete to substantially alter their hydration strategy while training, you need to consider the pros and cons. Will this change make them feel less comfortable while out on the run? Will it put them at greater risk for hyponatremia? Generally speaking, increasing hydration is rarely a bad thing, but having a conversation with your athlete and proceeding cautiously will increase your odds of success.
If your athlete is at higher risk or has suffered from a bone stress injury, you might err on the side of a slightly more aggressive hydration strategy. However, it is recommended to also pair this with assessing their load optimization, dialing in prehab exercises and discussing diet improvements.