Mountain Biking Injuries: Fitting Treatment to the Causes
Robert L. Kronisch, MD
THE PHYSICIAN AND SPORTSMEDICINE - VOL 26 - NO. 3 - MARCH 98
In Brief: Mountain bicyclists are subject to various traumatic and overuse injuries. Traumatic injuries range from minor abrasions and contusions to wrist fractures, shoulder injuries, and concussions. Helmet use is important in preventing serious head trauma. Many overuse injuries stem from improper bike fit, anatomic malalignments, and training errors. Treatment includes adjustments to the bike and modification of training habits. Included are tables regarding a variety of malalignments, related overuse injuries, and suggested bicycle adjustments. A companion article ("How to Fit a Mountain Bike") provides guidance for doctors and patients on proper bike fit.
During the past 20 years, off-road bicycling, or mountain biking, has grown from its origins on a California hillside to a worldwide sport with a multibillion dollar market. Mountain bikes now account for more than half of US bicycle sales and are owned by at least 25 million Americans (1). This tremendous growth has fueled the bicycle industry, and technical innovations and new designs flood the market each year. Competition within the sport has also increased, and over 85,000 Americans now participate in organized races annually (2). Rising international participation led to the first Olympic mountain bike race at the 1996 summer games in Atlanta.
With the increased popularity of the sport has come an increased number of injuries. Research regarding these injuries has begun to reveal injury patterns in the sport. Awareness of these patterns as well as the unique character and demands of the sport can help healthcare professionals manage the traumatic and overuse injuries that mountain bikers may sustain.
The Shape of the Sport
Although the physiologic characteristics of elite mountain bikers are similar to those of elite road cyclists (3), the differences in equipment, terrain, and competition make the two activities distinct. The mountain bicycle has evolved far from the road bicycle, and many models are now constructed of exotic materials shaped in new geometries that have departed considerably from the standard double-triangle steel bike design. Wide knobby tires with lower inflation pressures, advanced braking systems, and shock-absorbing suspensions make the mountain bike suitable for off-road riding.
The cross-country race is the most popular form of competition and typically involves a large number of riders that must maneuver an uphill and downhill course for 2 to 3 hours. Other types of competition include the downhill race, an individual, 5- to 10-minute time trial in which speeds may exceed 50 miles per hour. The dual slalom event has an elimination format and takes place on a pair of short downhill courses featuring multiple gates and small jumps.
Whether off-road cyclists are competitors or recreational riders, the rough, varied terrain they negotiate places a premium on bike-handling skills and makes them vulnerable to acute and chronic injuries. Although these injuries may resemble road-biking injuries, the contributing factors are often quite distinct.
Unfortunately, crashes appear to be inherent in off-road bicycling. More than 80% of 650 mountain bikers who participated in surveys (4-7) were injured in off-road crashes during a 1-year period. However, many of those injuries were minor and self-treated. In one study (7), 20% reported a traumatic injury in the preceding year that was severe enough to require medical attention and limit their ability to ride.
Types and incidence. Most crashes result in only minor injuries such as abrasions, contusions, and lacerations. These superficial wounds accounted for 60% to 70% of injuries in most studies (7-11). Fractures and concussions are less common (20% to 30% and 3% to 12% of injuries requiring medical attention, respectively) but have been consistently reported (7-11). The majority of fractures occur to the upper extremity and most commonly involve the fingers, metacarpals, wrist, and radial head.
The shoulder is particularly vulnerable to injury. Clavicle fractures and acromioclavicular separations commonly occur when a cyclist falls and lands on the shoulder. Shoulder dislocations can occur if the cyclist's arm is raised during a forward fall.
Serious injuries have been reported, including pelvic fractures (12), intra-abdominal injuries (13), facial fractures (14), and severe brain injuries (11,15). One death from a head injury in an unhelmeted off-road cyclist has been reported (11).
Fortunately, helmets are used by 80% to 90% of off-road cyclists (4,7,11). One study (11) found that mountain bikers were more than four times as likely as other cyclists to wear helmets, which probably accounts for the low rate of head injuries in the sport.
Contributing factors. A number of factors contribute to acute injuries. A retrospective survey (4) of recreational mountain bikers found that off-road crashes were commonly associated with excessive speed, unfamiliar terrain, inattentiveness, and riding beyond one's ability. A similar survey (7) of recreational and competitive off-road cyclists identified loss of control, high-speed descent, and competition as factors related to acute injuries; competitors were four times more likely than noncompetitors to be acutely injured.
Many studies (4-10) indicate that the majority of injuries take place on downhill rides. Flat tires and other mechanical problems are more commonly associated with accidents that occur during downhill than during cross-country races (9,10). Other causes of accidents are multifactorial and include hitting a bump or rock during a high-speed descent, losing traction while turning, or losing control of the bike while riding too fast (8).
Whatever the cause, injuries tend to be more severe when a rider is thrown forward over the handlebars than when he or she falls off the bike to the side (9,10). In one study, female cross-country racers were more likely to be thrown forward off their bikes and injured than their male counterparts (10).
Prevention strategies. To prevent injuries, the importance of bicycle maintenance, bike-handling skills, and common sense cannot be overemphasized. Helmet use is clearly effective in decreasing head injuries and should remain a key preventive measure (11,16). However, since most bicycle helmets provide little protection to the lower face (15,17), some helmets have been redesigned to offer improved facial protection, and these are especially popular among downhillers. Significant facial injuries have still occurred despite the use of these newer helmets (author's unpublished data, July 1997), and the optimally protective mountain bike helmet is probably yet to be developed.
Other protective gear, such as chest, shoulder, and extremity padding, is also used by many downhill cyclists. These devices probably help decrease superficial injuries to the bicyclist, but their ability to prevent serious injury has not been demonstrated (9).
Like other cyclists, mountain bikers can suffer overuse injuries. Such injuries have been studied little in mountain bikers, but studies in road cyclists indicate that overuse injuries of the knee are common (18). Other overuse syndromes have also been reported, including problems in other parts of the lower extremity (19), the spine (20), upper extremity (21), and saddle region (22). In one study (7) involving 265 off-road cyclists, 30% had recently experienced knee pain associated with mountain biking, and 37% reported low-back pain while riding; wrist pain and hand numbness were each reported by 19%.
Contributing factors. Overuse injuries in off-road cyclists are related to interactions between the cyclist's body, the bicycle, and the terrain on which they ride. The effects of anatomic variations and small errors in bike fit are magnified by long hours spent riding and by highly repetitive lower-extremity motions. A combination of these factors is usually responsible for overuse injuries of the lower extremity. In contrast, upper- body overuse syndromes are more often related to weight bearing on the handlebars and vibrations transmitted from rough riding surfaces to the cyclist via the bicycle.
Training errors frequently contribute to overuse injuries. The abundance of hills available for off-road riding can easily tempt a rider to push beyond his or her established level of conditioning, especially early in the season. Common training errors include inadequate preseason conditioning, riding in too high a gear by overrelying on the large chainring, and suddenly increasing mileage, hill climbing, or riding intensity.
Evaluation, treatment, and prevention. The office evaluation of a cycling overuse injury should include a training history to detect common training errors. Riders should be encouraged to establish a basic level of conditioning at the beginning of the season before increasing their mileage, hill climbing, or intensity. Injured cyclists may require temporary modifications of their riding habits until symptoms decrease. Rather than taking a complete break from cycling, the injured off-road cyclist can often benefit from relative rest, ie, temporarily decreasing mileage and hill climbing and emphasizing low-resistance easy pedaling with avoidance of the large chainring. As symptoms subside, the cyclist can gradually increase the amount and level of riding.
The physical examination should include a search for anatomic variations that could negatively interact with the mechanical restraints of the bicycle. When present, these malalignments can usually be compensated for with adjustments to the bicycle, as described in table 1 (19). The cyclist's position on the bicycle should be checked whenever possible by following the guidelines that accompany this article. (See "How to Fit a Mountain Bike." ) The riding position thus obtained is considered a neutral position and is a good starting point for most riders. Sometimes an overuse injury can be treated simply by putting the cyclist in a neutral riding position. If this treatment does not resolve the symptoms or if a cyclist with an overuse injury already rides in a neutral position, specific adjustments to the bicycle may be indicated (18-22). Adjustments to consider for a number of common problems are summarized in table 2.
For lower-extremity problems such as tendinitis and patellofemoral pain, the key to successful treatment is usually in detecting ana-tomic malalignments or errors in bike fit and correcting the rider's position on the bicycle with adjustments to the saddle and pedals. Upper- body syndromes such as ulnar nerve compression and neck soreness often respond to unloading of the upper extremities by raising the handlebars and/or decreasing the cyclist's reach. Adding or adjusting a front suspension system and allowing the elbows to flex during rough riding may also be helpful in relieving upper-body symptoms. Low-back pain is often related to inflexibility and inadequate conditioning and tends to decrease as the season progresses. Raising the handlebars early in the season and gradually lowering them to the desired position as flexibility and conditioning improve may be helpful to some cyclists with low-back pain.
Other treatment options for overuse injuries in off-road cyclists include all of the same approaches used with other athletes, such as physical therapy, ice, and anti-inflammatory medication. However, without attention to the bicycle as well as the bicyclist, overuse injuries are likely to persist.
Back to the Slopes
The rapid evolution of the mountain bike and off-road cycling in recent years suggests that veteran and new participants share a remarkable enthusiasm for their sport. Healthcare professionals who understand the nature of the sport and the types of injuries mountain bikers may sustain can help return injured off-road cyclists confidently to the trails.
Dr Kronisch is a staff physician and sports medicine consultant at the San Jose State University student health center in San Jose, California. He is a member of the American College of Sports Medicine and the American Medical Society for Sports Medicine. Address mail to Robert L. Kronisch, MD, San Jose State University, Student Health Center, 1 Washington Square, San Jose, CA 95192; e-mail to [email protected].
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