Bone Density and Runners
When it comes to making sure your bones are in top shape, you might think that popping a calcium supplement is going to get the job done. In fact, you might need a time machine. Bone density might not seem like a very big deal when you’re 10, but the activities you do as a kid and up to age 25 actually have lasting impact on the strength of your bones for the rest of your life. According to a UK study, even the age at which you first walk as a baby has a bearing on how strong your bones will be as a teenager. Up until age 25, our bones respond to weight-bearing exercise by becoming denser, stronger, and thicker. As we move toward middle age, this capacity diminishes somewhat (especially at the ends of bones). The effect is still present, albeit to a lesser degree, when we subject our bones to impact stress like running or boxing, or load our bones along their lengths by lifting free weights.
Side note: Why free weights? Unless you’re using machines because you’re injured or doing physio on the advice of a PT, free weights will always give you more bang for your buck because they require more of your body to be engaged. Squatting, for example, is more useful than using a leg press machine, since the force of the weight when squatting is distributed along the spine, through to the pelvis and leg bones. Leg pressing in a machine offers limited benefit in comparison, as the movement disengages a large portion of the chain of movement, loading the leg bones in isolation.
The neat thing about impact and bone density is that the effect is specific to the part of the body experiencing stress. It’s not a systemic adaptation, it’s localised to the area doing the work. Think of a tree that grows on a windy hill versus one growing in a sheltered forest. The tree on the hill will develop a thicker, gnarled, strong trunk, and the sheltered tree will grow taller. The taller tree maybe more useful from a lumber standpoint, but it will also be more fragile. Bones may not be trees (and they won’t become gnarled and twisted in response to weight lifting) but they react to external stimulus in a similar way - if you subject your skeleton to progressive stress, it will adapt to the new input by creating denser bones.
An easy illustration is available when we look at professional tennis players; experiencing repeated impact with the dominant arm results in one significantly stronger humerus. Oh, and those tennis players also had stronger lumbar spines and femoral neck, indicating that all that sprinting around the court pays off in spades. It would seem that a bit of impact is actually a good thing, and avoiding impact at all costs can actually be detrimental to your skeletal health.
Our bodies are kind of amazing, though. Look at what happens after just one bout of impact work like jumping up and down. In this study, subjects jumped until they were exhausted, and their blood work showed signs of bone turnover within 48 hours. It’s almost like your skeleton is asking you to bounce around!
For runners, the legs, pelvis, and spine receive the bulk of the benefit. (This is a strong argument for upper body weight training to supplement a running program, unless you like the idea of titanium legs and brittle arms.) If you do some hill work on the Bionic Runner you will notice that the upper body gets a great workout as you sway the BR from side to side to muscle up those hills.
It’s fun to go down the rabbit hole on bone density science because for so many years we’ve heard that impactful sports like running are harmful to our joints and spines. In fact, running actually improves the strength and resilience of cervical discs and it increases bone density. Now, as always, context is important. Carefully monitored ramp-ups of running activity is always a good idea and it although running is good for bone density and cervical discs, too much of a good thing is bad for your joints and cartilage. But for those worried that their knees or back will “wear out”, new research is showing evidence to the contrary. Use it or lose it, as they say; just be smart about it.
It is all about thinking that running is for life and not overdoing it or over training. Overtraining is the leading cause of injury among runners. It is a balancing act between bone density, fitness training, form training, injury and running for life. A smart approach is to divide running fitness training from running form training. Running form training helps us to improve running economy, whereas running fitness training causes physiological adaptions to increase the oxidation of fuel by running muscles and to deal with the carbon dioxide and lactic acid produced. One way to do this is through a running specific running fitness training machine. By specifically recruiting and stressing the same muscles as running, the Bionic Runner’s 60:40 swing vs stance phase timing causes similar physiological adaptations to improve running-specific fitness.
Aging athletes will be happy to hear that running reduces age-related bone loss, making it an effective measure in preventing osteoporosis. The only catch? Once you stop running (or weight training) regularly, it’s business as usual as far as losing bone density and strength is concerned. Some of the reduced effect on bone density of weight-bearing exercises in elderly people may be because older, deconditioned folk just don’t have the conditioning to exert the necessary amount of force. After all, it’s not just about whacking your skeleton over and over, you also need the musculature to support your chosen activity.
The science is in: if you want to stay capable as you age, you’ve got to use what you’ve got starting now. Use common sense, of course, and don’t dive into an ultramarathon right off the couch. Ramping up mileage and pace in a reasonable manner will go a long way to keeping your magical skeleton injury-free. While running is a great choice when it comes to preserving bone density, don’t neglect your upper body; give those arms and shoulders some heavy love. You can perform things like weights or push-ups, or even better go for some extra miles on the Bionic Runner and exercise all your upper body as well as your core and legs. Your future self will thank you. And if you were a sedentary kid or a late walker, don’t despair! Your body is still an incredible bone factory, given the right circumstances.
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