Mountain Biking

Definitions

• The term “mountain biking” broadly refers to riding bikes with specific design characteristics in various off-road settings.

• Mountain bikes generally differ from road bikes in several ways: a smaller frame, stronger wheels, larger range of gears, a wider flat or upright handlebar, hydraulic brakes, suspension, and wider, knobby tires.

• There are many riding and bike types, with some overlap between bikes and riding styles.

• The five main mountain biking categories are cross-country (XC), trail/all-mountain (AM), downhill (DH), Enduro (essentially hybrid between DH and AM), and freeride (FR), which includes trials and urban riding (TR) ( Fig. 95.1 ).

  

Demographics

• Participation is open to all age groups, with the average age dependent on the type of biking; 22–36 years is the gross average, with most competitors aged between 19 and 44 years. There are more males than females, but female participation is increasing; the sport is especially popular among young males.

• Mountain bikes are the largest category of bikes sold in US bike shops.

• Racing/competition is now common in XC, Enduro, DH, FR, and other styles.

• The sport attracts risk-tolerant personalities.

• The number of noncompetitive mountain bikers is increasing; less is known about their injury epidemiology. The National Interscholastic Cycling Association (NICA), founded in 2012 in the United States and currently with individual leagues in 30 states, has led to an impressive upsurge in participation in mountain biking, primarily XC racing, in thousands of children and adolescents since its inception, both on junior developmental teams (“Devo,” grades 7–8) and high schoolers. There were 22,752 participants nationwide in 2019 alone. The NICA has developed a surveillance system for coaches, riders, and parents to report and collect injury data for high school student-athletes to improve our knowledge of injury epidemiology, especially in young riders.

Research

• Injuries are reported inconsistently in the literature, ranging from specific injuries to general types of injury (e.g., laceration, fracture) to injured body areas (e.g., joint, upper or lower extremity, head).

• Early data are from competitive XC; more data are now available from all areas: XC, DH, Enduro, and FR. Although recreational data are still sparse, more large organizations and events (i.e., Enduro World Series, Olympic Games data) have begun surveillance and reporting injuries.

• Available studies are primarily descriptive and focus mainly on epidemiology or injuries themselves (generally defined by body or joint area); there are fewer details available regarding mechanisms of injury.

• Most injury studies have a preponderance of male participants (75%–80%). Many studies depend on victim recall.

Competition

• XC still popular, but a shift to Enduro, DH, and other events is being seen.

  • The origin of NICA has led to the addition of a number of high school races (XC) in participating leagues

• Categories are established based on age, gender, and rider skill.

• Rider skill categories were changed in 2009 (applicable to riders 15 years of age and above): Pro, Category 1 (previously Expert), Category 2 (previously Sport), and Category 3 (previously Beginner); previous riders classified as “Semi-Pro” must choose between the new Pro or Category 1 tiers. Some races still use classification categories of novice/beginner, sport, expert, and elite/pro.

• Age categories: Youth (<10 years old), Junior (10–18 years old), Under 23 (19–22 years old), Senior (23–29 years old), and Master (>30 years old)

Protective Equipment

• Protective torso armor and extremity padding: Primarily for FR and DH; use of lighter, flexible pads increasing in XC

• Helmet designs: Full face (mainly DH, FR) and standard (mainly XC, Trail/AM); helmets should be Snell-, Consumer Product Safety Commission (CPSC)-, or American National Standards Institute (ANSI)-approved and tested. Recommend replacement after any significant crash.

• Shorts: Multiple types of synthetic moisture-wicking chamois; some have built-in hip padding; loose-fitting shorts with inner chamois are becoming more popular

• Gloves: Varying thickness, with shell protection (dorsal fingers and hand) and padding

• Eyewear: Ultraviolet protection, shatterproof, changeable light-reducing and colored lenses for varying conditions; clear lenses for night/low light riding; goggles in DH and extreme cold

Mountain Bike Fit

• May start with a professional fit (see Chapter 94 : “Road Biking”).

• Mountain bike fit not as straightforward as road fit; use the initial road fit to help achieve a mountain bike fit window (an ideal, individualized fit that may deviate slightly from a virtual perfect fit).

• Correct fit important for prevention and treatment of acute and chronic injuries

Physiology

• High-intensity sport—generally higher (especially XC) than road stage races

• XC circuits span 1–2 hours (depending on age/racing category), performed at a heart rate (HR) of approximately 90% (±3%) of HRmax, corresponding to a $\dot{\text{V}}$ O ₂ max of approximately 84%; more than 80% of race time is spent above the lactate threshold (LT).

• Intensity is related to a fast start, several climbs, rolling resistance, and isometric and eccentric arm and leg muscle contractions that are required for shock absorption, bike handling, and stability over rough terrains (increases HR response to submaximal cycling).

• Start has fundamental importance to the entire race. XC races are generally on single track (narrow trail where only one biker could fit); however, typically start on a wider course (either paved or dirt road) and race to the single-track portion to achieve a good position; fast starts and early steep climbs lead to high intensity and HRmax early in the race.

• Anaerobic energy systems taxed, especially during steep climbs (require high power output: up to 250–500 watts); anaerobic power and ability to sustain high work rates for prolonged periods are prerequisites for competing in high-level off-road cycling events.

• Various factors may affect off-road XC performance, especially in elite cyclists: $\dot{\text{V}}$ O ₂ max, peak power output (PPO), power output (PO), and $\dot{\text{V}}$ O ₂ at the ventilatory threshold (VT) and at the respiratory compression threshold (RCT); studies are conflicting regarding which is most important:

  • PO and $\dot{\text{V}}$ O ₂ at the RCT normalized to body mass are predictors of off-road performance times.

  • $\dot{\text{V}}$ O ₂ max, PPO, and LT normalized to body mass correlate with XC performance in some studies.

  • PO at the VT may correlate with time trial performance.

• Body mass is a factor: power-to-weight characteristics are important for success in off-road events; high power-to-weight ratio is good for strong hill climbing ability; higher mass may assist with rapid descents.

• Factors other than aerobic power and capacity may affect off-road cycling performance: cycling experience and economy (specificity of principle); technical ability; and nutrition before, during, and after competition.

Training

• Need to develop good aerobic endurance, anaerobic capacity, overall muscle strength, good coordination, balance, and bike-handling skills.

• Significant upper body and core muscular strength is necessary for repeated isometric and/or eccentric muscle contractions required to absorb shocks and constantly adjust to changing terrain; accomplished using weight training and riding off-road.

• Many competitive XC riders train for 10–14 hours weekly; some XC racers train systematically in a similar fashion to road racers. Others train with much less structure.

• Athletes ride at varying aerobic and anaerobic intensities (zones); it is helpful to use an HR monitor.

• Mountain bikers train both on- and off-road.

  • Use different types of training in a similar manner to other endurance events (listed in order of decreasing intensity): race pace, intervals and hills, speed and tempo, endurance, strength, and recovery.

  • Training cycle (depends on peaking goals): base (4 months), intensity (4 months), peak (4–6 weeks), racing (8–12 weeks), or recovery (4–6 weeks).

  • Off-road terrain incorporates various training types and is less flexible than road riding under controlled intensity.

  • Long off-road rides over rough, technical terrain, especially if at altitude, require longer recovery compared with equidistant road rides.

  • Use periodization and monitor overtraining, especially if training at high altitude and/or frequently on rough terrain.

  • More injuries reported during training than during competitions, where there is less access to medical personnel and treatment.

Epidemiology

• Injury types and numbers likely grossly underreported secondary to varying and limited study design, difference in injury definitions, understudy of a large population of recreational and noncompetitive aggressive riders in all styles.

• Peak incidence: June to August

• Mixed competition and noncompetition data indicate that 50%–90% of riders have been injured in the previous year; one study showed 20% had a significant injury requiring medical attention and were prevented from cycling for at least 1 day; competitive cyclists were injured more than recreational cyclists in earlier studies, but unclear if this still reflects the current trend.

• Reported injury rates (multiyear data) is as low as 0.45%–0.6% per year in XC, DH, and DS competitions; 0.30% injury rate for recreational cyclists, but some reports are higher; definition of injury rate may vary (e.g., number of injured cyclists per number of starts per 100; number of injured cyclists per 100 hours of race time).

• Injury rates are greater for DH versus XC relative to time spent on bike (0.37 injuries per 100 hours on bike for XC vs. 4.34 injuries per 100 hours on bike for DH).

• There is a possible association between increased hours on bike and injury severity, but some data indicate the presence of fewer injuries in competitive cyclists who spent 1 hour per week more on the bike during the competition season and 3.5 hours per week more on bike during the off-season compared with those who experienced major injuries.

• A large study with 2029 competitive Enduro riders showed an injury rate of 8.9% in 10 events; almost a third of the injuries occurred in inexperienced riders (those who only raced one previous Enduro World Series event).

• Cannot extrapolate injury data from road bikers because road bike crashes are often specific to riding on pavement; many more collisions with motor vehicles, which is rare in off-road cycling (a few case reports of serious injury resulting from mountain bike–motor vehicle collisions do exist)

• Experienced cyclists injure bones and joints more frequently than beginners.

• Injuries tend to occur when riding downhill or losing control. Professional DH racers are more likely to sustain injuries than amateurs.

• Young males are the most frequently injured population because of the popularity of the sport in this group and the likelihood to engage in aggressive and technically demanding riding styles.

• In high school riders, most common injured areas include head/brain, wrist/hand, shoulder, and knee (in order).

• Injury risk in competing females appears higher than in males, but injury severity is higher in males than in females.

  • Risk factors in females: loss of bike control, poor upper extremity strength, fewer riding years

• The number of injuries occurring during racing and training are about equal, but traumatic injuries are more common in races, whereas overuse injuries are more common in training.

Mechanisms of Injury and Risk Factors

• Most commonly reported: excessive speed, unfamiliar terrain, loss of control (encompasses multiple factors), inattentiveness, riding beyond ability, and riding DH, slippery terrain (approximately 90% may be viewed as errors in judgment) ( Table 95.1 )

  Table 95.1

  Specific Reported Causes and Risk Factors

  Rider-related	Errors in judgment and riding technique Excessive speed Inattentiveness Riding beyond ability and loss of control Incorrect braking Improper training and overtraining Female or young male Intoxication No helmet; especially children
  Bike/equipment-related	Mechanical failures (more common in DH): flat tires, brakes, chains, forks, handlebars, pedals, suspension parts, seatposts, frames Improper fit
  Terrain-related	Surface: mud, gravel, loose dirt, wet Unfamiliarity Downhill Obstacles and jumps
  Environment-related	Competition Heat Cold Sun Lightning Orienteering mishaps Animals and reptiles (attacks and collisions)

• Most crashes occur while riding DH.

• Injuries from loss of control, loss of traction, and mechanical failure result in similar injury patterns.

• Special attention is applied to the cyclist–bike–terrain interface and how it relates to injuries.

Evaluation

General Treatment

• General treatment approaches for traumatic and overuse injuries in off-road cyclists are similar to approaches used with other athletes (e.g., physical therapy, cryotherapy, antiinflammatory medication).

• Specific cycling injury diagnosis and treatment is a highly individualized area; affected by multiple variables, including training, experience, riding style/type, and bike fit.

• Treatment options

  • Relative rest and activity modification: temporarily decrease mileage, intensity, hill work; spin using low-resistance and high-cadence pedaling; correct training errors.

  • Bike fit: consider placing rider back to neutral position, especially if bike was never fit; adjust from there

  • Medication: nonsteroidal antiinflammatory drugs (NSAIDs) for analgesia and inflammation, bacitracin ointment for soft tissue trauma

  • Heat and ice: ice appropriate overuse injuries after rides and intermittently throughout day; keep the affected joint warm during ride (e.g., knee warmers)

  • Physical therapy (see specific injuries)

    • Lower extremity (especially hamstring, iliotibial band) flexibility

    • Back and neck flexibility

    • Strengthening: lower extremity (eccentric programs for Achilles, patellar, and hamstring tendinopathy), dynamic core stabilization

    • Plyometrics, proprioceptive, and other cycling-specific coordination training

    • Deep tissue massage and release techniques

    • Neural stretching maneuvers

  • Bracing, strapping, or taping where appropriate

    • Knee: soft patellofemoral brace, infrapatellar strap, McConnell taping

    • Hand and wrist: use an off-the-shelf wrist or thumb spica splint (can bend steel stay to handlebar, most cycling gloves fit over), custom-molded orthosis (e.g., Orthoplast)

  • Corticosteroid injection

    • Upper extremity: carpal tunnel syndrome, de Quervain tenosynovitis, intersection syndrome

    • Lower extremity: pes anserine bursitis, trochanteric bursitis, iliotibial band syndrome, Morton neuroma

Overuse Injuries