Pedal towards greater impact routes

Cyclists are no strangers to breaks and fractures. But Andrew Coggan could be forgiven for not expecting a hip fracture from a bicycle crash at 30 years of age.

He may have been less surprised than most of his peers though, having recently been diagnosed with low bone density. For many cyclists, bones are not as strong as they should be.

Although cyclists are known for staying on top of their training for heart-rate zones and pedal cadence, research suggests they should also pay attention to their risk of thinning bones.

“Sometimes athletes in their late twenties and early thirties will come in for a femur or a hip fracture — and they'll be surprised because the fall was not that bad,'' says Dr Max Testa, a sports medicine physician at the Orthopaedic Speciality Hospital in Salt Lake City.

“But we'll look at the X-rays and see there is osteopenia [lower-than-normal bone density].''

Stress it out

Many factors contribute to osteopenia or osteoporosis (low bone-mineral density) in cyclists. But one of the culprits is the nature of the exercise.

Cycling is a low-impact sport that puts little mechanical load on the bones.

That's great if you have joint problems but it's the weight-bearing nature of exercise that signals bones to create more mass.

Without such stress, bones don't get stronger, making them more prone to injury.

Avid cyclists seem to be especially at risk of bone injuries if they don't do any cross-training.

The lower spine is a susceptible area because it gets almost no loading. The hips may get some from pedalling.

Coggan, now a scientist and exercise physiologist at Washington University, St Louis, had been cycling one to two hours a day for about 15 years when he crashed in 1989.

Comparative study

A recent study in the journal Medicine & Science in Sports & Exercise found that competitive male road cyclists had lower bone-mineral density in their spines than a control group of men who were moderately physically active while doing other recreational activities.

They were also more likely to have osteopenia and osteoporosis than those in the control group, despite the fact that the cyclists had a greater calcium intake.

Another study, published in the journal Bone in 2002, found that male road cyclists had lower bone-mineral density than male mountain bikers, after adjusting for body weight and controlling for age.

The difference there could be that mountain biking, with its bumps and jumps, perhaps provides more impact and stimulation for bone growth.

Young cyclists aren't immune. “You don't achieve peak bone mass until your late twenties,'' says Debra Bemben, an associate professor in the health and exercise science department at the University of Oklahoma.

“If cyclists are in their early twenties and they're not doing anything else for exercise that's going to load their spine and help them achieve peak bone mass, it may put them at risk if they fall, since they'll have a greater chance of fracture.''
Good diet necessary

Further, some hard-core cyclists may not be eating enough to offset what they burn when exercising, depriving their bodies of bone-strengthening nutrients such as calcium and vitamin D.

Especially at risk are women who have eating disorders, menstrual disruptions and bone loss — known as the “female athlete triad''.

“With a deficit in the energy balance,'' Bemben says, “the body is not able to build up bones.''

That caloric shortfall could also trigger other physiological problems, such as hormone imbalances.

For women, this could mean lower oestrogen levels and for men, lower testosterone levels.

Bemben says oestrogen and testosterone have protective effects on bones, slowing the rate of bone breakdown.

But hormones aren't only affected by calories. “If people overexercise, it can suppress testosterone in men, as it can suppress oestrogen in women,'' says Dr Aurelia Nattiv, director of the Santa Monica-UCLA Osteoporosis Centre.

However, studies have not always borne out the connection between low testosterone and low bone density.

Although the subject pops up on cycling message boards, it's not a hot topic. “Some people have no clue,'' Testa says. “They don't even know it's an issue.''

A dual energy X-ray absorptiometry (DXA) scan is most often used to test bone density, a non-invasive test that uses low levels of radiation.

Young male cyclists think they're healthy and don't need to be concerned.

Some sports medicine physicians, orthopaedists and cycling coaches discuss the issue with patients but Testa and others say more education may be necessary.

Check-up alert for cyclists

Cyclists who may be at risk for osteopenia or osteoporosis include those who have been cycling for years without doing any other activity, are very thin, have a family history of osteoporosis or are postmenopausal.

Those athletes should consult a physician to see if any treatment or test is necessary, such as a bone-density scan, known as a DXA (not all insurance plans cover the test).

They should also discuss lifestyle changes, such as eating more food that contains protein and essential bone-building nutrients — such as calcium and vitamin D.

A registered dietitian — preferably one who has worked with athletes — can help design a meal plan that includes key foods. And, of course, they should cross-train.

Cross-training for cyclists doesn't require hours of doing other exercises. Some light strength-training can help build bone mass.

Squats are especially good for loading the spine. Jumping rope — or just jumping — also provides impact the bones need.

Running, football and basketball are good plyometric sports but doing too much too soon could cause fractures, especially if bones are already compromised.

Keep in mind that bone loss can't be reversed overnight. Depending on the severity of the loss, it may take months or even years to see an improvement in bone-mineral density.