I heard that bouldering increases bone density in a climber's hands, while climbing routes does not. Is that true? Also, what is the significance of increased bone density?
Pat Bagley, Weston, Massachusetts
My inner child is coughing. The issue of bone-strength adaptation is a little more complex than that. For starters, there are no studies looking at this specific issue, so it is theoretical with regard to scampering on rocks, whatever your penchant, bouldering or routes.
I assume you are talking about bone strength, which is both bone mineral density (BMD) and bone size (BS), i.e. wall thickness, cavity size and total area, among other parameters.
The crux of your question involves five variables: high-intensity exercise versus more endurance-based activity (bouldering and route climbing, respectively), the two aforementioned indices of bone strength, and time. Any adaptation is specific to the amount of load at the site in question.
Current research suggests that high load and low repetition will increase BMD, as well as bone size, faster than endurance-based activity in the relative short term.
Route climbing does not really fit into the endurance category, but rather somewhere in the middle of the power-endurance continuum. As such, you could argue that bouldering, which is positioned at the far end, produces greater gains in bone strength in the short term due to its higher intensity and greater rest period between bouts.
Recent studies illustrate cortical hypertrophy (bigger bones) in climbers, but since many comp climbers use bouldering as a training medium, and this was not a control parameter, this is not a definitive result. I suggest that if bouldering and route climbing were separated, boulderers would show more bone adaptation than climbers of a similar standard who did not train finger power. But it's a Paris Hilton study a no-brainer complete with hair splitting.
Most of this is really only pertinent for post menopausal women, since bone strength, BMD and bone mass are not especially significant for the average climber other than a curious footnote.
To answer your question: Yes, you will have stronger bones in your fingers, and to a lesser extent in your arms, if you boulder a lot. More so than for route climbing. If you drink a lot of cola this may be negated, however, since cola is known to reduce BMD!
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