Avoiding Cycle Injuries

Sean Fyfe highlights the importance of bike set-up in avoiding cycling injuries.

“In 2003 I was lucky enough to have the opportunity to venture into the Pyrenees mountain range in the south of France to witness the penultimate mountain stage of the Tour de France. It was one of the greatest stages in recent years, when Lance Armstrong fell off his bike in the final ascent only to remount, attack and put the winning time on Jan Ullrich to clinch his fifth consecutive tour victory. I had watched the tour on TV before, but it wasn’t until I was on the mountain that I could grasp the passion and fanaticism surrounding the sport of cycling. Injury to any cyclist with even the smallest amount of the commitment I saw on the mountain that memorable day would be devastating.

Fortunately, in the sports injury world cycling is more often a benign force than a cause of trouble. Because it is low impact, it provides many people who otherwise would struggle to perform regular exercise with the chance to stay healthy and active. Among recreational and competitive cyclists, compared to high impact sports such as road running, the rate of injury is favourable and injuries are often easier to prevent and address.

Nevertheless, clinicians should have a clear appreciation of the sport’s biomechanics and in particular how bike set-up relates to injury. It can often be something as simple as a small change in bike or shoe set-up that is the direct cause of an injury, so unless this is accounted for during assessment and management, the injury will never be properly resolved.

Acute cycle injury
Because cycling is such a widespread leisure activity (and bicycle ownership almost endemic), injury statistics are not hugely informative. US figures, for instance, estimate that 85 million Americans are cyclists; and of these 540,000 end up in hospital accident and emergency departments each year. Among the casualties, 67,000 have head injuries and 600 die (1).

For any competitive cyclist, to train on the road is to accept the risk of serious injury, because of the twin hazards of vehicle traffic and speed. A multitude of orthopaedic injuries occur with high-speed accidents, but of most concern are head injuries. As a result of fatal injuries during competitive cycling, the compulsory use of helmets has been in place for a number of years at the Tour de France, except for the finishing climb in the mountain stages. In Australia, all cyclists (from everyday users to pro competitors) are required to wear helmets or face hefty fines. Throughout Europe, by contrast, there is no such compulsion. Despite legislation and campaigns promoting awareness of cyclists to other road users, acute injuries in cycling will always be a big concern for those participating in the on-road sport.

Chronic injury
Several studies highlight the neck and back as the main sources of overuse injuries. After a six- to eight-day cycling tour for recreational cyclists, Wilber et al reported that 54.9% of females and 44.2% of males presented with neck pain for medical treatment, and 30% of both males and females with back pain (2). Patterson et al (3) analysed ulnar and median nerve palsy “often referred to as ‘cyclist’s palsy’ “after a 600km bicycle ride. Of the 25 riders given physical and questionnaire assessments, 23 had either motor or sensory symptoms. Most symptoms were reported in the hands in the ulnar nerve distribution.

Wilber et al (2) found 85% of cyclists suffering with one or more overuse injuries: 48.8% had neck problems, 41.7% had knee trouble, 36.1% groin and buttocks, 31.1% hands and 30.3% backs. The study also found that female cyclists are approximately 1.5 times more likely than males to develop neck symptoms. Although neck symptoms are the most common, in my experience knee injuries are of more concern, as they pose a greater long-term risk.

Biomechanics
A single pedal cycle involves a power phase from 12 o’clock to 6 o’clock and a recovery phase from 6 o’clock to 12 o’clock. The power phase delivers most of the force that generates forward momentum. This force is produced via the extensors of the lower limb chain: quadriceps, glut max, hamstrings (working at the hip) and calves (working at the ankle). The recovery phase also contributes to overall power delivered in one cycle by the upward pull of the attached shoes via the flexors: hip flexors, hamstrings (working at the knee) and calves (working at the knee).

At 12 o’clock, the knee is flexed to 110 degrees and then extends 75 degrees through the power phase to 35 degrees flexion at the beginning of the recovery phase. It is important to note that during the power phase the knee will drift medially because of the normal valgus orientation of the femoral condyles (more pronounced in females).

The foot pronates during the power phase, imparting an internally rotating force to the knee, much the same as during the stance phase of running, thereby increasing the stress to the inner side of the knee. The opposite happens during the recovery phase in preparation for another power phase. At the bottom of the power phase the foot should be parallel to the ground. The lumbar and thoracic spine have to tolerate prolonged flexion and the cervical spine prolonged extension.

Assessment of chronic injury
When a cyclist presents with an overuse injury, the clinician needs to gain an understanding of the following areas to determine the underlying cause:

the athlete’s anatomical alignment
musculoskeletal function
bike set-up
training history and changes in regime.
It is imperative that the athlete’s bike is correctly adjusted to suit their specific anatomical alignment, in order to achieve bike-body harmony. Static measurements are useful of:

left and right leg length
Q angle (alignment of the shaft of the femur with the tibia)
foot position relative to the tibia (degree of external or internal rotation)
foot alignment (including heel position relative to the tibia, forefoot position relative to the heel and big toe position).
For each injury, the therapist should be aware of the relevant flexibility and muscle balances in order to establish technique faults contributing to injury (for instance, the cyclist may be medially deviating with the left knee or the pelvis may be dropping to the right when the right foot reaches 6 o’clock).

Bike set-up
Correct bike set-up is crucial both to maximise performance and to avoid injuries. But very few recreational cyclists are aware of this. If you venture on to the roads on a Sunday morning, you will see droves of cyclists with their seats set too high or their knees grossly deviating left and right.

Table 1 below sets out the key positions that the clinician should ensure their client is achieving in the set-up of their bike.

(The cleat is a plastic piece screwed into the bottom of the shoe to enable the rider to clip into the pedal.)

Bike set-up can be assisted greatly by two small pieces of equipment: full shoe-length leg raises compensate for leg-length discrepancies, and forefoot varus wedges placed between the cleat and shoe correct knee alignment by allowing the foot to operate in its normal position. Specific cycling orthotics are also commonly used.

The cyclist also needs to be made aware that they should adjust their bike set-up to suit variables such as the length of race or competitive goal in order to achieve the best balance of efficiency and comfort. In endurance races, the rider will usually opt for a slightly less aerodynamic position to improve comfort, whereas for a short time trial, the tightest possible aerodynamic position and lowest trunk position will deliver maximum speed advantage.

Chronic injury risks
Knee

When pedalling, the largest force produced acts through the knee up to 5,000 times an hour, so it is no wonder that the slightest incorrect distribution in load can end up in a serious knee injury. Table 2 below summarises the main injury risks.

Ongoing soft tiss