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British Medical Bulletin Advance Access originally published online on February 21, 2008
British Medical Bulletin 2008 85(1):101-112; doi:10.1093/bmb/ldn009
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© The Author 2008. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oxfordjournals.org

Mountain biking injuries: a review

Michael R. Carmont

The Hartshill Orthopaedic Surgical Unit, The University Hospital of North Staffordshire, Stoke-on-Trent ST4 6QG, UK

Correspondence to: M. R. Carmont Specialist Registrar Orthopaedic Surgery The Hartshill Orthopaedic Surgical Unit The Department of Trauma and Orthopaedic Surgery The University Hospital of North Staffordshire Stoke-on-Trent ST4 6QG UK E-mail: mcarmont{at}hotmail.com


   Abstract
Top
 Abstract
Introduction
 Historical background
 Methods and results
 Limitations of research
 Future prevention
 Future research
 Summary
 References
 
Introduction: Mountain biking is a fast, exciting adventure sport with increasing numbers of participants and competitions.

Methods and results: A search of PubMed, Medline, CINAHL, DH data, and Embase databases was performed using the following keywords: mountain, biking and injuries. This revealed 2 review articles, 17 case controlled studies, 4 case series and 5 case reports. This review summarises the published literature on mountain biking injuries, discusses injury frequency and common injury mechanisms.

Conclusions: Riders are quick to adopt safety measures. Helmet usage is now increasingly common and handlebar adaptations have been discontinued. Although the sport has a reputation for speed and risk with research and awareness, injury prevention measures are being adopted making the sport as safe as possible.

Keywords: mountain biking • injury


   Introduction
Top
 Abstract
 Introduction
Historical background
 Methods and results
 Limitations of research
 Future prevention
 Future research
 Summary
 References
 
Mountain biking is a fast, exciting adventure sport with increasing numbers of participants and competitions. This article reviews and compares the published literature on mountain-biking injuries, discusses injury frequency, common injury mechanisms and specific injuries related to mountain bike riding.


   Historical background
Top
 Abstract
 Introduction
 Historical background
Methods and results
 Limitations of research
 Future prevention
 Future research
 Summary
 References
 
In the western world, the mountain bike is the most popular type of bicycle to ride and off road cycling as a recreational activity is currently enjoying a period of popularity. Competitive off road cycling or mountain biking is also increasingly popular. There is an annual World Cup Series and a World Championships organised by the governing body the Union Cycliste Internationale (UCI) and after demonstration at the Atlanta Olympic Games in 1996; the mountain biking was awarded full Olympic status at the 2000 Games in Sydney.1

MTB competitions were previously limited to the disciplines of Cross Country and Downhill, but more recently Dual Slalom or four Cross and Free or Trials riding have developed. Cross-Country races require considerable stamina and may last over several hours, whereas Downhill events may be over within a couple of minutes. During downhill racing speeds approaching 70 mph may be obtained over treacherous rocky terrain. At such speeds, the slightest loss of attention can lead to a high-speed crash with obvious consequences of injury. During four cross and Dual Slalom races, riders race head to head over a prepared artificial course. Although physical contact is not allowed, riders jostle with each other for the best line and so falls commonly occur. Free or Trials riding involves performing stunts and jumps over obstacles. Speeds are low, but the height from riders may fall is considerable.

Mountain biking has a reputation as a fast, exciting adventure sport that is rapidly developing. This review demonstrates how research has followed the sport progression and how mountain-biking injuries are more appreciated.


   Methods and results
Top
 Abstract
 Introduction
 Historical background
 Methods and results
Limitations of research
 Future prevention
 Future research
 Summary
 References
 
A search of PubMed, Medline, CINAHL, DH data and Embase databases was performed using the following keywords: mountain, biking and injuries.

This revealed 2 review articles,2,3 17 case-controlled studies and cross-sectional surveys,4–20 6 case series and 5 case reports. There was one prospective study. These studies are presented in Table 1.


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  		Table 1 Published case controlled studies and cross sectional surveys of mountain biking injuries

 
Injury rates and demographics

In summary, the risks of injury are 0.49% for cross-country riding and 0.51% for downhill. Injury rates are 0.37 riders per 100 h cross country and 4.34 riders per 100 h downhill racing.

More serious injuries to the head and neck occur whilst falling over the handlebars rather than falling off the bike to the side, which tends to result in lower limb injuries. As a consequence of this, female riders, who are lighter and as a result fall over the handlebars easier than male, tend to be more seriously injured than male riders; however, most injuries sustained mountain biking occur to young males aged 20–39 years.

Aetiological factors of injury are loss of control, high-speed descend and competitive activity, i.e. riders are most likely to be injured racing downhill rather than training. Turning, loss of traction and mechanical problems can also lead to injury.

The commonest injuries (60–75%) are soft-tissue abrasions, lacerations and contusions. The commonest fracture is the clavicle and the commonest dislocation is the acromioclavicular joint.


   Limitations of research
Top
 Abstract
 Introduction
 Historical background
 Methods and results
 Limitations of research
Future prevention
 Future research
 Summary
 References
 
Although there are many studies reporting mountain-biking injury, it is difficult to compare these directly and extrapolate information. These studies range from the cross-sectional survey of the readership of MTB magazines to the interview of injured riders at national and international competitions.

One of the key difficulties is the determination of when an injury has occurred. This difficulty is not just restricted to mountain biking and occurs in other sports.21 Self-reported injuries may vary from superficial abrasions and contusions to life-threatening falls. Some studies have tried to define injuries as to whether the rider is unable to complete an event if an injury occurs during competition or if a rider subsequently misses a days riding. The extreme nature of MTB competitors must be considered and certainly in downhill events, riders are very ‘pumped up’ and may complete events even with significant injuries, e.g. fractures, if they are mechanically able to ride.

Questionnaire surveys may be more accurate than event-side medical care reporting, as riders may note abrasions and contusions on a survey of recreational riders but professional riders may not consider these to be significant enough injuries to trouble event medical support. Surveys may more accurately report a prolonged period of potential exposure compared with the duration of a single or series of events.

Some studies have used standardised assessment tools such as the Abbreviated Injury Scale22 or the Injury Severity Score.23 These tend to be studies at relatively large trauma units for monitoring hospital admissions and may not necessarily reflect the true frequency of injury. The use of speciality referral, i.e. fracture clinic, may show a higher proportion of fractures and may suggest a higher frequency of required operative intervention. It is not surprising that a few injured riders presenting to medical services over a short period of time can overwhelm local resources.24 The American studies tend to involve riders racing on dirt and gravel mountain roads at ski areas. Within Europe the terrain may be more mixed, involving grass, woodland and even small proportion of tarmac surface. These differing terrain types may produce different injury patterns.

Specific injury patterns

There are several studies and case reports focussing on specific anatomical areas, and these deserve further discussion. These include the head and face, the cervical spine, the upper limbs, the abdominal viscera, the perineum and the lower limbs.

Head and face
 Kelly has reported that 13% of sport-related head injuries presenting to an emergency department were sustained whilst cycling.25 But in McDermott's study of 1710 bicycling injuries, helmet use has reduced the risk of head injuries by 39% and the risk of facial injury by 28%.26 The importance of head protection has been appreciated with the majority of off-road MTB riders wearing helmets 15.

Head injury has even resulted in a dislocation of the incus into the external auditory meatus,27 so protection for the whole of the cranial vault must be considered.

Bicyclists and mountain bikers are prone to facial trauma, and Chow28 has suggested that conventional bicycle helmets may not provide adequate protection for the face whilst mountain biking.28 MTB riders have more severe injury profiles than bicyclists for maxillofacial trauma with 55% having facial bone fractures, 22% having dentoalveolar injuries and 23% having soft tissue injuries. Dentoalveolar injuries were the commonest site of facial injury in road bicyclists (50.8%).11,12 Of the facial fractures, 15.2% was maxillary fractures.

Dental injuries can also occur. This may range from the chipping of teeth to the degloving of the mandibular mucosa.29 The high incidence of facial trauma has led to the increased use of helmets with attached face protectors and face guards. The use of dental guards has not been reported; however, this is likely to be negligible.

Cervical spine
 With the speeds involved in downhill racing and the frequency, mechanism and forces involved in over the handlebar falls, it is surprising that more cervical spine injuries have not been reported. A fall onto the top of the head could result in a flexion injury, whereas a fall onto the face could results in hyperextension.30 A series of three patients have been left paraplegic as following falls from mountain bikes.31 The riders in this series had sustained either over the handle bar falls or falls directly onto the helmet. The cervical spine is the commonest site of spinal injury and cord injury was present in 24% of Kim's series of patients.20

Upper limbs
 The upper limb extremities have already been identified as an area commonly injured whilst falling from the bike. This may be either in an attempt to stop the fall by outstretching a hand or in an attempt to protect injury to the face or head. In Rajapaske's series of forearm injuries, the distal radius and scaphoid were commonly injured bones (30 and 28%, respectively); however, surprisingly the commonest fracture was the radial head (35%).7 Prolonged cycle riding of any form, as been shown to be associated with nerve compression at the wrist by Patterson, with 92% riders reporting sensory or motor or both symptoms32 and hypothenar hammer syndrome, i.e. Ulna artery occlusion, has been reported with the vibrations of off road riding.33

Abdominal viscera
 Large series of patients with liver haematomata sustained during mountain-biking crashes have been reported.34 All of these patients had blunt focal blows to the right side of the abdomen due to the handlebars, and all were using ‘bar ends’ on their handle bars. These forward facing bar extensions allow additional riding positions for comfort and energy efficiency. Following a media information programme of the implication of bar ends for abdominal injury in Austria, bar ends cease to be used in mountain biking. Nehoda's group have noticed an almost complete cessation of liver injury from the sport.

Kim20 has shown that the spleen was the organ most frequently injured (49%); the liver (15%) was injured less commonly. The small bowel was the most frequently injured hollow organ (13%).20

Perineum
 Perineal numbess due to nerve compression after long periods of sitting on a hard saddle will be familiar to the majority of riders,35 and modern saddles are moulded to reduce pressure on the pudendal nerves in the perineum.

The scrotal contents can be subjected to repeated microtraumatisation during mountain biking. A total of 96% of mountain bikers had pathological abnormalities of scrotal contents compared with 16% of a control group on ultra sound examination.16 The most common abnormal ultrasound findings were scrotal calculi (81%), epididymal cysts (46%), epididymal calcifications (40%), testicular calcifications (32%), hydoceles (28%) and varicoceles (11%).36 Short padding and alteration of the saddle position could help reduce this incidence.

It is not just the male genitalia which have been shown to suffer from prolonged riding. Female road cyclists have been reported to develop unilateral vulval hypertrophy.37 A case of external iliac artery occlusion has been reported in a young female cyclist although this is not thought to have a gender predeliction.38

Lower limbs
 The shins of bikers are vulnerable to scratches and scrapes when riding through undergrowth, but this can be minimised by wearing long trousers, gaiters or shin guards. Riders find it essential to have a firm foothold on the pedal to permit stability and straps, or quick release pedals have been developed for this purpose. Quick release pedals hold the shoe securely onto the pedal improving power transfer,39 but conversely make it more difficult to put the foot down onto the ground when dismounting or falling off. This delay in foot release means that there is less time to put the foot down for support, so it is placed closer to the bike and the sharp teeth of the chain ring. The sharp teeth can result in significant pretibial lacerations, an area prone to poor healing and Patel has reported a series which required debridement under anaesthesia and skin grafting.40 Failure to remove the foot from the pedal can result in the cyclist toppling over onto their side. These falls can result in a direct blow to the hip resulting in a neck of femur fractures41 or acetabulum fractures.42

Although classically described falling off horses with the foot caught in the stirrup, Lisfranc's dislocation of the mid-foot has also been described in a mountain biker. In Callaghan's case rather than having the foot caught in the toe clip, pain occurred as the rider suffered a forced plantar flexion injury of the midfoot whilst trying to put his foot on the ground.43


   Future prevention
Top
 Abstract
 Introduction
 Historical background
 Methods and results
 Limitations of research
 Future prevention
Future research
 Summary
 References
 
This review recommends that riders should be well trained, ride within the level of their capability, learn to dismount safely and use a well-maintained bike without handlebar ends. They should also wear helmets with facial protection, padded gloves and shorts, use cushioned seats and shin protection.


   Future research
Top
 Abstract
 Introduction
 Historical background
 Methods and results
 Limitations of research
 Future prevention
 Future research
Summary
 References
 
The gold standard of the randomised, prospective, controlled study is probably impossible to perform in this sport as riders will always take steps and alter their riding to prevent injury. Comparative cohort studies for injury prevention have been performed retrospectively; therefore, it is possible that the highest standard of research possible is being performed.


   Summary
Top
 Abstract
 Introduction
 Historical background
 Methods and results
 Limitations of research
 Future prevention
 Future research
 Summary
References
 
Mountain biking is a fast, exciting adventure sport that may lead to serious injury. However, the majority of injuries are minor and can be minimised with care and precautions.

Accepted for publication January 1, 2008.


   References
Top
 Abstract
 Introduction
 Historical background
 Methods and results
 Limitations of research
 Future prevention
 Future research
 Summary
 References
 

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This Article
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