A Khanna, E Bagouri, N Gougoulias, N Maffulli
A Khanna, E Bagouri, N Gougoulias, N Maffulli. Injuries in Enduro riders. The Internet Journal of Orthopedic Surgery. 2008 Volume 11 Number 2.
Enduro is an off road motorcycling event. It is a fast, exciting adventure sport with increasing numbers of participants and competitions. This article reviews the published literature on physiology, risk factors and specific injuries in Enduro riders.
Enduro started in 1913 to test the reliability and endurance of man and machine. Although the term Enduro often applies to any type of long-distance, off-road motorcycle races, its true technical definition usually refers to a set of rules, varying by the events' governing body, that specify exactly when a rider should arrive at certain pre-defined locations along a prescribed route. The object of the event is to reach those locations exactly per the defined schedule, with early or late arrivals resulting in penalties to the riders' scores. Enduro thus refers specifically to time keeping events. Races, on the other hand, are simply a course that has a start and finish, and the competitors try to race to achieve the fastest time from start to finish123.
In Enduro, if the engine breaks down, drivers have to fix it themselves. No outside help is allowed. Furthermore, driver’s expertise is “examined” in difficult grounds (forests, stone ground), and their maximum speed is recorded. There are 6 members in each team and their penalty points are added. Failure of a driver to reach the defined locations can bring a team from first to last rank. As there is no option for substitution, the drivers are ‘forced’ to participate sometimes even if there are reasons not to (injuries, not fit, etc). If a driver stops, that affects the points that can be earned by the team; hence, the injured driver is examined by his team doctor first. Some national teams even have their own mobile X-ray machines, so that they can quickly examine the injured driver123.
With the increasing popularity of this event, Enduro is staged at many levels from local events through to National, Continental and World Championships 123.
The time challenge, when added to the physical, environmental and technical difficulties which riders face on uneven and slippery courses, coupled with the pressure on the driver to keep going even if injured, makes Enduro an exciting and dangerous sport. In the present article, we explore the physiological aspects of Enduro riders, mechanism of injury sustained by these riders, and review the literature on various types of injuries sustained by them.
Material and methods
A search of PubMed, Medline, CINAHL, and Embase databases was performed using the following keywords ‘Enduro injuries’, ‘off-road motorcycle injuries’ and ‘Enduro sport’. Studies dealing with Enduro or off road motorcycling events were identified, and their bibliographies thoroughly reviewed to identify further related articles. This search identified 4 studies which investigated the physiological characteristic of Enduro riders and explored the injury pattern sustained by these athletes.
Physiological aspects of Enduro riders
Scientific information on the physiological characteristic of competitive off-road motorcycle riders is scanty. Gobbi et al 4 found that Enduro riders are on the upper range of the normal weight, with a mean Body Mass Index of 24.5+/-0.3 and a body fat percentage of 12.6+- 3.7 %. This weight makes Enduro riders susceptible to injuries, as it makes it more difficult to control the motorbike during the turns and in muddy ground, especially when going up or down hills 4.
The duration of the competition and the frequent changes of direction and speed due to the characteristics of the circuit require constant involvement of all the muscle groups in the body. Therefore, both aerobic and anaerobic metabolisms are involved in Enduro 45. Lactate levels within 2 minutes after the race are 1.5+-0.3 mM, and increase to 3.8+-1.3 mM after high speed trials. Lactate accumulation leads to muscle fatigue and decreases the muscle force available for control of the motorcycle 46.
The Vo2max (maximal oxygen uptake) achieved in the upper limbs in Enduro riders is between 64% and 80% of the lower limbs Vo2max 47, suggesting that the work generated by the lower limbs in Enduro riders was greater than the upper limbs. This could be the reason why the ankle and foot are the most common sites for severe injuries in Enduro riders.
In untrained subjects, there is a significant difference in handgrip strength between the dominant and non-dominant limb. These differences reflect the greater use of the dominant arm in normal daily activities8. In Enduro riders, however, the force used for handgrip was similar in the right and left hands (506+_52 N and 506+_47 N respectively) 4. Despite the similar hand grip strengths between the two hands, the occurrence of carpal tunnel like symptoms is higher on the right than the left, presumably from greater handling of the throttle, which changes the flexion angle of the wrist by the right hand 9.
Mechanism of Injury
The most common mechanism of injury was collision with an immobile object followed by loss of traction and collision with mobile object including other motorcycles. The rest of the injuries arose from jumping from the motorcycle, loss of control from high speed wobble, when the motorcycle starts to oscillate. In few injuries, the rider suffered from post-traumatic amnesia and was unable to recall the mechanism 310.
Two third of the injured riders were ejected from their bikes either over the handle bar (48%) or to the right and left sides (30% and 22% respectively), while 3% were ejected backwards. The hands and arms were the most common landing points (37%), followed by shoulders (29.3%) then the hips and buttocks (12%). Some riders, however, landed on their feet (5%), and others on their head (6%) or back (2%) 310.
The severity of injury did not correlate with the speed at the time of accident and experience. This has been attributed to the fact that speed correlated with the amount of training and experience. Therefore, riders who were injured at higher speeds were usually highly trained seasoned participants10.
Overuse injuries have also been explored in Enduro riders9. Exposure to vibration of a motorcycle engine increased the incidence of transient carpal tunnel syndrome and forearm pain in these athletes.
Anatomical distribution of injuries
A) Extremities injuries
The extremities are the most injured parts in Enduro, but 98% of these injuries are mild to moderate, with Abbreviated Injury scale 10 grades 1 and 2. Most of the reported injuries are ligamentous or fractures and dislocations, occur with almost equal percentages (47% and 46%). The remaining injuries were muscular strains310.
1) Upper Limb
Upper limb injuries constituted 57% of the total injuries, and they involved ligamentous injuries to the shoulder girdle (eg. acromio-clavicular dislocation). Fractures and dislocations were mainly to hand and wrist, accounting for 23% of the total fractures, followed by fractures to the humerus and clavicle. Other injuries included shoulder and wrist dislocation 310.
The hands, the wrists and the forearms are the predominant areas of overuse in Enduro riders, with symptoms suggesting carpal tunnel syndrome and transient forearm muscle tenderness 9.
2) Lower Limb
Lower limb injuries accounted 43% of the total injuries to the extremities. Most of the ligamentous injuries were strains of the collateral ligaments of the knee. Ankle and foot were the most commonly involved areas in fractures and dislocations (36%), with half of these fractures were to the phalanges and metatarsals. Hip dislocation has also been reported 310.
B) Head Injuries
Injuries to the head constituted 9% of the total injuries, with concussion as the main diagnostic finding. Facial bone fractures associated with fractured dislocated mandible, broken teeth and facial laceration have also been documented 310.
C) Abdomen and Thorax injuries
Most of the abdominal and thoracic injuries arose from blunt trauma which resulted in bruises, broken ribs and abdominal contusions 310.
D) Spinal injuries
The spinal injuries accounted for 5% of the total injuries. Most cases were mild strains to the cervical and lumber spine, with no fractures or dislocations 310.
E) Muscular injuries
Muscular strains were reported in only 7% of injured Enduro riders 310.
Although motorcycling competitions are considered dangerous 111213 , Enduro has proved to be relatively safe, with 85% of the injuries being mild with mean Injury Severity Score14 of 3.9, involving one anatomical area 310. This could be due to the fact that the very few studies, with limited number of subjects, exist in the literature focusing on this rapidly growing sport.
Keeping riders in bikes, which may be achieved by changes to the bike design, can help to decrease the severity of the injuries. Some changes to the clothing, such as provision of additional protection to the ankle and foot, which are the parts most commonly fractured, may be considered. Also it has been suggested that substitutes should be allowed, the number of extra tasks should be reduced, the whole area where the race takes place should be better monitored, and, in bad weather, the time limits should be wider3.
In depth understanding of the physiological aspect of Enduro riders with close monitoring of injuries is needed to promote safety measures in Enduro and to reduce risk factors of injury. In turn, this can help to make Enduro a safe alternative to other dangerous motorcycling sports.
Mr Anil Khanna,
DePuy International Implant Research Fellow
Department of Trauma and Orthopaedic Surgery,
Keele University School of Medicine,
Stoke on Trent