Bone health

Cyclists are prone to low bone density. We ask Dr Steven Hawkins how best to avoid it

- David Bradford

Why are bones, especially in cyclists, prone to losing density?

Bone density is a reflection of how much mineral is in the bone, primarily calcium. We experience a loss of bone mineral with ageing but we also know that there is a relationship with physical activity - cycling is one such activity associated with reduced bone density.

What is going on in the bone when this happens?

Partly it is to do with impeded bone renewal; bone is a structural material unique in how it can remodel and replace damaged areas. But certain activities or hormonal changes can disrupt this process. Bone tends to remodel to withstand the force it is experiencing, so if you only do activities with very low loading forces, the bone adapts to become a weaker structure. In the same way, a heavier person puts more force through their skeleton so will usually have stronger bones than someone with low body mass.

Why is this a particular issue for cyclists?

There are very low loading forces in cycling; the bike supports the weight and so there are minimal gravitational forces acting on the bones. Muscle forces are important to bone, but those produced in cycling do not have a significant impact on the areas of the skeleton most at risk from osteoporosis - the lumbar spine, top of the femur bone, and the distal radius [wrist].

Which types of activity most benefit bone health?

Research has shown that it has to involve high stress, either through impact or muscle pull, and it should not be repetitive - if it's too repetitive, the stimulus is reduced. Cycling ticks none of these boxes, and worse still, when high-volume road cyclists are not on their bikes, they tend to be in recovery, so even normal, everyday loading is reduced. Competitive cyclists seem to be most at risk.

Is the problem compounded by under-fuelling?