Compared to many sports, cycling is one with a relatively low injury rate. Crashes and collisions apart, cycling is almost impact free – good for your joints and muscles.
In addition, you can also select your desired gear to match the terrain, which means 
that you can avoid loading your 
muscles and joints with excessive force, keeping the cranks spinning rather than pushing a big gear.

The icing on the cake is that because your feet are fixed in place, spinning the cranks requires very 
little co-ordination, which also 
reduces the risk of injury due to poor technique. Still, despite all these advantages, cyclists can, and regularly do, suffer overuse injuries, particularly when spending long, hard hours in the saddle – for example, when preparing for a big sportive.

It’s the back

Given how hard your legs work on the bike, it’s natural to assume that when an overuse injury strikes, it’s your knees that will be most vulnerable. Surprisingly however, the research says otherwise.

When Norwegian scientists investigated 116 professional road cyclists and looked at the types of overuse injuries suffered over the previous year, some startling facts emerged: 94 per cent of the cyclists had suffered some kind of overuse injury during that period.

Of these, 45 per cent were to the lower back with only 23 per cent to the knees; 58 per cent of all the cyclists had experienced lower-back pain in the previous 12 months, and 41 per cent of all cyclists had sought medical attention for it.

What’s surprising about these results is that cycling is a low-impact sport and is often actually recommended for back pain sufferers. So why is lower-back pain so common among cyclists who spend long hours in the saddle?

The first, and most obvious, thing to look at is the way the bike is set up. Choosing a bike frame with the right geometry and ensuring the correct riding position on the bike (see the box below) are both crucial to minimising unwanted loading on your lower back as well as your knees, shoulders and neck.

If your bike set-up is only fractionally out, the cumulative effects of thousands upon thousands of repeated pedal revolutions and countless hours sustaining a less than ideal posture can become significant – even if you have the toughest back to begin with.

Don’t blame your bike
Correct bike set-up is crucial for back health, but in the study on elite cyclists above, they were supervised by national coaches with access to advanced facilities, so incorrect bike geometry wouldn’t have been a factor. What else could be going on? Well, some research has shown that muscle fatigue may play a role.

In one study, scientists demonstrated that when cyclists pedalled to exhaustion, their hamstrings (rear thigh) and calf muscles became progressively more fatigued (as expected). What was surprising, was that this fatigue seemed to produce undesirable changes in muscle movement patterns, which then affected the back – specifically, the degree to which the cyclists were bent forward in the lumbar region and also how far their knees were splayed out.

In a nutshell, the more tired these cyclists became in their legs, the worse their spinal posture became.

Impaired spinal movement
Another study looked at the effects of holding a static bent-forward (flexion) position on the all-important back extensor muscles that help maintain correct posture and stability in the lower back.

It found that after prolonged periods of static flexion (when a cyclist is on the drops), these muscles became less effective at generating the forces required to maintain spinal stability and posture.

More evidence for this effect comes from Australian research, which compared nine healthy (symptom-free) cyclists and nine cyclists with chronic lower-back pain. In short, the researchers found that the cyclists in the pain group tended to have excessive increased lower back flexion (forward bending in the lower back), which was associated with reduced activity of deep low-back muscles called multifidus – key stabilisers of the lumbar spine.

The notion of impaired spinal-movement patterns as a major cause of lower-back pain in cyclists is also supported by Belgian research, which found that cyclists measured riding their own bikes, and who were chronic lower-back pain sufferers, tended to ride with more flexion in the lower lumbar spine. They also tended to experience a steady increase in pain over a two-hour period compared to healthy cyclists.

The scientists concluded that rather than poor bike set-up, it was the cyclists’ impaired motor control patterns in the lumbar region that led to poor movement patterns, specifically excessive flexion, resulting in lower back pain.

Selecting correct frame geometry
Adjusting the bike set-up to reduce injury risk (see the opposite page) is essential, but perhaps even more fundamental is to begin with the correct frame geometry. All the different parameters shown below will affect the way the bike handles, but A, B and H (seat tube, top tube and head tube length) need to be correctly matched to your body dimensions.

A Seat tube length
B Top tube length
C Head tube angle
D Seat tube angle
E Fork offset
F Rear centre
G Wheelbase
H Head tube length

Optimum bike set-up 
to minimise injury risk
Saddle height This should be positioned so that when the pedal is at the bottom of the stroke and the ball of your foot is on the pedal, your knee should have a slight bend in it. Hips shouldn’t move sideways during crank 
rotation and you shouldn’t have to stretch at the bottom of the pedal stroke.

Saddle angle This should be in a horizontal position, parallel with the floor when viewed side on (but sometimes a very slight downwards tilt can be helpful for those who experience a lot of pressure in the perineum area).

Forwards/backwards position of the saddle With the pedals adjusted so that they are at the three o’clock and nine o’clock positions, a vertical line dropped from just behind the kneecap on the outside of the forward knee should pass through the axle of the pedal.

Handlebar position Handlebars should be adjusted so that you neither have to stretch to reach them, or feel confined by having them too close to your body. You should be able to comfortably reach the bars from an upright position and your elbows should be slightly bent when resting on them.

This article was first published in the Winter 2012 issue of Cycling Fitness. You can also read our magazines on Zinio, Google Play, Nook or download from the Apple store and also through Kindle Fire.