Introduction
The number of cyclists in the United States has grown substantially over the past 10 years, according to the League of American Bicyclists (46). The health benefits of cycling have been clearly established by research, with studies showing consistent positive dose-response relationships between the amount of cycling and improved fitness, decreased risk of all-cause mortality, cardiovascular disease, colon cancer morbidity, and obesity (32). Societal benefits of a modal shift from car travel to cycling also have been shown, including a reduction in air pollution and traffic accidents (26). In addition to its health benefits, however, cycling also is associated with a variety of injuries (12,19, 25,41). Nontraumatic (overuse and degenerative) injuries predominate within recreational cyclists (47), though those who travel at high speeds, in large groups, over technical terrain, or in traffic may be at risk for traumatic injury. In a study of elite cyclists during a multiday road race, half of the injuries documented were traumatic, most involving skin and soft tissue (49). A recent survey of elite British cyclists found that training injuries were more prevalent, but competition injuries were more severe (33).
Overview of Cycling
Cyclists take to the roads and trails for recreation, transportation, and competition, and the demands of each type of cycling dictate the necessary equipment, as well as potential for injury. Competitive cycling includes the disciplines of road racing, time trial, cyclocross, mountain biking, track, BMX, and triathlon. Road bicycles are generally light, stiff, and aerodynamic, to allow the rider to transfer power efficiently but also to maintain comfort throughout several hours of riding at a time. Cyclocross, a discipline where handling is emphasized as much as power, and where courses venture off-road, requires a machine that will handle a variety of terrain. Similar to a mountain bike, these bicycles use wider tires and braking systems less likely to get clogged with mud, but with a geometry that allows the rider maximum control while sacrificing only the minimum of speed (Fig. 1). In solo events such as time trial and triathlon, where riders are prohibited from drafting or riding in groups, a unique bicycle frame geometry and triathlon-specific “aero” handlebars with forearm rests allow a more aerodynamic position. This decrease in wind resistance can make a major difference in speed for a given fitness level (10,17).
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Figure 1: Cyclocross requires a bicycle that will enable the rider to handle a variety of terrain and obstacles, including the dirt descent shown. Photo by Christopher McIntosh, Boston MA.
The low-impact nature of cycling makes it an appropriate component of rehabilitation, as well as a fitness activity for adults with degenerative joints (31). Bicycling on level surfaces is nearly universally recommended by orthopedic surgeons after total hip and knee arthroplasty (43). A wonderfully unique quality of the bicycle is its ability to accommodate a wide variety of injuries and disabilities. For adaptive athletes, cycling offers options including handcycling for athletes with reduced lower extremity mobility, tandem cycling for athletes with visual impairment, and recumbent and/or three-wheel cycling for athletes with impaired balance.
Riding volume and training plans vary widely based on an individual’s goals. Bicycle commuters can essentially get extra workouts on their way to work, and year-round commuters with appropriate winter gear may log yearly mileages that rival their racing counterparts. Weather and daylight factor into training, with many riders training indoors or avoiding longer rides during the colder months and shorter days. It is important to note that there are physiologic differences between indoor and outdoor cycling (9,36), with research showing higher power output during outdoor riding despite the same RPE (29). With the development of new technology and devices, cyclists can record location, distance, elevation, HR, and power output for both personal use and the review of coaches or medical professionals.
Bicycle Fit
In addition to strength, fitness, and technique, the interface between the cyclist and the bicycle must be considered in the assessment of the cyclist. Bicycles are designed for specific demands, from racing performance, to comfort and stability in traffic, to carrying heavy loads or children. The frame geometry, handlebar shape, saddle, and pedal system are selected based on the desired body position and function (Fig. 2). Improper body position on the bicycle can contribute to a number of overuse ailments (6,25,41,42). Small adjustments, particularly at the body’s interface with the bicycle, can affect the rider’s biomechanics throughout the kinetic chain, improving comfort, efficiency, and power generation.
Figure 2: Road bicycle mounted on an indoor trainer. Relevant components impacting rider position and bicycle fit labeled.
A bike fit starts with a comprehensive interview regarding the cyclist’s needs and goals, followed by a physical examination focused on anatomical factors that impact bike fit, such as range of motion of the lumbar spine and hips. On-the-bike fitting begins with evaluation of the foot/shoe and cleat/pedal interface. Modern bicycles for racing or fitness typically use clipless pedal systems, where a cleat on the sole of the shoe attaches to the pedal. In the sagittal plane, the fitter assesses the knee position relative to the foot during pedaling. The assessment continues proximally to the pelvis and its contact with the saddle, which also impacts knee mechanics. The saddle position and shape will influence the rider’s comfort; pressure-mapping technology is becoming more common in assessment of this interface. A discussion of pelvic numbness, pain, or skin breakdown is essential. The attention then moves to the lumbar spine (with relation to an individual’s posture, strength, and flexibility) and continues to the shoulder girdle and cervical spine. The position of the lower body will influence the position of the upper body, which can be further adjusted through the handlebar position. Weight distribution between the seat and the hands is assessed and is typically slightly weighted toward the seat. In the frontal plane, the fitter assesses knee tracking and lateral pelvic and torso motion. The later stages of bike fit involve the individual riding for several weeks to identify areas of discomfort as well as any improvements in power output. Bike fit can be accomplished with simple tools such as a goniometer and plumb bob, or through advanced technology such as the Retül system, using motion capture to produce three-dimensional kinematic data. Importantly, the tools of a bike fitter are only as good as the fitter and do not replace a keen eye and understanding of biomechanics.
Prevention of Cycling-Related Injury
Prevention of cycling injury involves knowing the common mechanisms for traumatic and overuse injury, and early correction of strength and flexibility imbalances, technique errors, and bicycle fit.
Traumatic injury
Bicycle crashes may result from several factors, including poor infrastructure or road conditions, mechanical failure, operator error, or interaction with a motor vehicle (38). The majority of traumatic injuries in racing involve soft tissue and skin, followed by fractures and concussions (41,49). Traumatic cycling injuries tend to primarily affect the upper extremity and head, but also may affect the lower body (15,33,35). In a race situation, with riders traveling at high speeds in close proximity, mechanical failures or incidental contact such as a touch of wheels or a bump of shoulders may occur, and skill is required to maintain composure and trajectory. Following any crash, damage to the rider’s helmet, face, or neck should warrant a rapid medical evaluation. The Medicine of Cycling Concussion Consensus Statement outlines an in-race and postrace concussion assessment protocol for cycling (1).
USA Cycling, the governing body of competitive cycling in the United States, requires the use of approved helmets in all racing events (45). Currently, no federal or state helmet laws exist for adults participating in recreational cycling in the United States. There have been several studies looking at the role of helmets in preventing brain injury in cyclists (7,21,44), and the results are mixed. The biomechanical data are clear, in that helmets decrease acceleration and increase forces needed to crush the skull in laboratory testing (28). However, mandatory helmet laws, historically, have not always resulted in a decline in head injuries (16). The effect of bicycle helmets on societal health is intimately tied to the environment where one is cycling. In Copenhagen and Amsterdam, where dedicated cycling infrastructure is the norm, cyclists do not share the road with fast-moving car traffic. In these environments, a helmet law would likely deter people from cycling, potentially leading to a negative public health impact. Conversely, in places where cycling is relatively unsafe, helmets will do little to make it safer and a helmet law may only provide a small public health benefit (16).
A recent study found that in cities with bicycle share programs, there was a small increase in the proportion of bicycle injuries involving the head after the implementation of the program, which the authors associated with the lack of available helmets (23). However, there are no data regarding the proportions of helmeted and unhelmeted cyclists, or whether the cyclists were using the bike share program at the time of injury. Responses to the article point out that the total number of injuries, including head injuries, declined in cities with bike share programs after their implementation (14,39). In spite of the risk of bicycle riding in an American urban environment, for commuters who shift from a car to a bicycle, prior research has estimated that the cumulative health benefits heavily outweigh the risks by about 9 to 1 (26).
Nontraumatic/overuse injury
Cycling is dependent on the repetitive motion of a pedal stroke, from 60 to 120+ rpm for the duration of a ride. The most common areas of overuse injury in cycling are the knee, lumbar spine, cervical spine, buttock, Achilles tendon, wrists, and forearm (4,11,15,18,35). Because the motion of cycling primarily occurs in the sagittal plane, strength imbalances may develop that influence a cyclist’s susceptibility to injury elsewhere along the kinetic chain. A recurring theme, hip abductor weakness has been previously linked with injury, and the gluteus medius has been shown to have abnormal activation patterns in the lateral ankle sprain, patellofemoral pain, iliotibial band (ITB) friction syndrome, and anterior cruciate ligament injury (48), though it has not been specifically studied in cycling. The hip abductors impact lower extremity biomechanics through stabilization of the pelvis and prevention of excess torque about the knee joint. Difficulty recruiting these muscles during pedaling, due to weakness or lower back or hip pain (13), may lead to increased motion in the coronal plane, decreasing power and predisposing the cyclist to injury (5). Likewise, suboptimal foot position can result in an inefficient pedal stroke, reverberating up the kinetic chain to the knee, hip, lumbar spine, and beyond. Below are several examples of common overuse injuries seen in cycling. A description of contributing structural, training, and bicycle fit factors is found in the Table.
Table: Contributing factors to overuse injury in cycling.
Knee pain
Anterior knee pain is one of the most common complaints of cyclists, including patellofemoral pain and chondromalacia, patellar tendinosis, and quadriceps tendinosis (19). These conditions are thought to involve biomechanical changes resulting in increased or abnormally distributed patellar contact pressures at the knee (40). This may stem from suboptimal bike fit, training volume, or cycling technique, including heavier gearing, lower pedaling cadence, or excessive hill climbing. Likewise, low or anterior saddle position, or excessively long cranks (Fig. 2) increase the knee flexion angle at the top of the pedal stroke, resulting in increased patellofemoral contact pressure. Incorrect width between the feet on the pedals relative to the hips also may contribute to abnormal knee tracking. Decreased gluteus medius strength often accompanies the maltracking knee, as seen in the patellofemoral pain syndrome (8), and is often accompanied by contralateral pelvic tilt, valgus knee deviation, and foot pronation. In cyclists who display these characteristics, improving gluteus medius and vastus medialis obliquus recruitment as well as addressing foot and ankle alignment on the bike can improve knee mechanics and decrease pain.
Patellar and quadriceps tendinosis result from increased repetitive force on the respective tendons, related to excess traction while pedaling (25) as described above. The biomechanical and fit issues that accompany these tendinopathies are similar to that of the patellofemoral syndrome. In the case of an acute flare of tendon pain, activity and loads should be modified to decrease possible risk of chronic injury.
Similarly, abnormalities in patellar tracking, hip abduction strength, and bicycle fit also can contribute to distal ITB pain, resulting from friction of the ITB across the lateral femoral epicondyle. In full extension, the ITB lies anterior to the lateral femoral epicondyle; however, with flexion, it glides posteriorly, contacting the lateral femoral condyle in an “impingement zone” at less than 30° of knee flexion. During pedaling, the ITB is pulled anteriorly on the downstroke and posteriorly on the upstroke (25). The minimum knee flexion angle at the bottom of a pedal stroke is close to the impingement zone of the ITB; therefore, conditions of increased knee extension such as excessive saddle height or improper cleat position can contribute to a distal ITB friction syndrome, resulting in pain over the superolateral knee, sometimes radiating up into the lateral thigh (22).
Spine pain
Neck and low back pain are common complaints (11), particularly in athletes riding aggressively or in a triathlon-specific geometry requiring increased lumbar flexion (17). It is helpful to use a directional preference approach (20) in categorizing spine pain. In the lumbar spine, discogenic pain and radicular pain due to disc herniation are typically provoked by flexion, whereas back and radicular pain due to spinal or foraminal stenosis and facet-mediated pain are often symptomatic with extension. Cycling is a predominantly flexion-based activity, and all positions result in some degree of lumbar kyphosis (30) (Fig. 3). During an active flare of flexion-based discogenic pain or radiculopathy, cycling may trigger pain significantly. For a cyclist prone to flexion-based low back pain, bike fit should be adjusted to include a tolerable degree of lumbar flexion that does not adversely impact the handling of the bike. For the cyclist with facet-mediated pain, foraminal or central stenosis, often seen in older patients, cycling is typically well tolerated and may be an excellent approach to exercise for its benefits on both back pain as well as general health (31). Varying hand position during a ride or even adding midride stretches to minimize time spent in flexion may be helpful for the cyclist with back pain. Certainly, optimizing off-the-bike postural habits, hamstring flexibility and hip range of motion, core strength, and even lifting mechanics when carrying heavy cycling equipment is important in reducing the frequency and severity of flares.
Figure 3: Positions on a road bicycle, (from top left) A. Seated, hands on brake hoods. B. Seated, hands in drops. C. Standing, hands on brake hoods (often used for shorter climbs). D. Standing, hands in drops (often used for sprinting).
A lower, more aerodynamic position wherein the cervical spine is forced into extension and protraction also can contribute to neck pain and challenges the endurance of the cervical extensor muscles. This may improve with time and training (17), but radiation of pain to the upper extremities, numbness, tingling, or weakness warrants further evaluation and may be attributable to cervical radiculopathy or cervical spinal stenosis. During a flare of axial neck pain or cervical radiculopathy, adjustments including elevation of the stem and handlebars to decrease cervical extension can be helpful in the short term in allowing a cyclist to continue to ride. As with lumbar spine pathology, directional preference assessment and postural correction are often of use.
Groin, buttock, and genital pain
No discussion of cycling-related injuries would be complete without mention of injury occurring at the rider’s contact with the saddle, at the ischial tuberosities and pubic rami, depending on their position and forward tilt. Ischial tuberosity width, which is measurable, will influence saddle selection, as will pelvis shape and overall bicycle fit. A more forward position with weight over the pubic rami is compatible with a narrower saddle, whereas an upright position with weight over the ischial tuberosities requires a wider saddle. Saddles vary based on width, shape, slope, cutout, and material. There are women-specific saddles, based on reported sex-related differences in saddle loading (34,37). Optimization of overall bike fit (not solely changes in saddle type) will affect weight distribution, in order to minimize discomfort (4).
Skin breakdown, or “saddle sores,” can develop because of improper bike fit, inappropriate saddle shape, or lack of necessary lubrication. In some cases, ischial hygromas or abscesses may develop. Skin breakdown in the cyclist can be challenging to treat, requiring time off the bike and, in more extensive cases, drainage or debridement.
Genitourinary symptoms related to bicycling include perineal or genital pain, paresthesias, dysuria, and sexual dysfunction. Pudendal paresthesias and neuralgia also are a challenging problem thought to be related to excessive pressure on the soft tissues of the perineum (24). The pudendal nerve arises from the sacral nerve roots, courses beneath the pelvis, passing through greater sciatic foramen, lateral to the ischial spine, through the lesser sciatic foramen into Alcock’s canal, where it is relatively fixed to the dorsal surface of the sacrospinous ligament (27). In this location, it is vulnerable to a variety of forces. The exact etiology of the neuralgia is not clear and may be related to pressure, traction, ischemia, or vibration.
Risk factors for pudendal paresthesias and neuralgia include poor bike fit, increased time in the saddle (time trialing and indoor riding), minimal position change, and increased body weight (4). Treatments aim to decrease pressure on the perineal tissues and pudendal nerve, and include time off the bike, modification of bike fit and saddle type, and incorporation of pressure reliefs. Physical therapy focusing on correcting strength imbalances and, in some cases, manual therapy or pelvic floor physical therapy may be helpful. In more recalcitrant cases, injections such as pudendal nerve blocks or pulsed radiofrequency lesioning of the pudendal nerve are available.
Ankle and foot pain
Through the use of stiff-soled cycling shoes, the cyclist’s foot becomes a rigid lever for power transfer to the pedal. Achilles tendon pain may develop with a softer shoe, more flat/flexible arch (pes planus), improper cleat position (foot posterior relative to pedal), or excessive ankle motion during the pedal stroke. A low saddle position increases dorsiflexion at the bottom of the pedal stroke to generate power, increasing tension on the Achilles tendon (42); excessive saddle height also may contribute to Achilles pain because of increased plantarflexion. Cleat position, typically anterior, may generate symptoms by increasing dorsiflexion. Adjustment of bicycle fit and use of cycling-specific orthotics (which correct foot position from the forefoot) may be helpful in correcting overuse injury of the ankle.
Cyclists are prone to discomfort and sensory changes in the foot, including metatarsalgia and interdigital neuralgia, often related to stiff-soled cycling shoes. Symptoms tend to be worse with longer rides or tighter fitting shoes. Cycling relies on forefoot and midfoot contact without weight in the heel; therefore, cycling-specific orthotics are constructed with all posting done in the forefoot, often through a varus wedge. Modification of cycling foot mechanics involves appropriate shoe sizing, toe box width, and cleat placement, and may include appropriate orthotics to assist in support and foot position. Foot orthotics have been found to increase midfoot contact area and peak pressures under the hallux, better perceived arch support, with no evidence of increased power generation (50).
Hand pain/numbness
Distal ulnar neuropathy has been described in the cyclist and is typically attributed to prolonged pressure on the handlebars causing injury to the ulnar nerve at Guyon’s canal in the wrist. The incidence of hand pain and numbness varies widely depending on study (19). Electrophysiologic changes have been shown after a long-distance multiday cycling event, including prolonged motor latencies of the deep branch of the ulnar nerve to the first dorsal interosseous muscle. Although worsening of median neuropathy was not generally seen, the cyclists that had prolonged baseline median motor latency did display worsening, and one did develop carpal tunnel symptoms (3). Contributing factors include suboptimal weight distribution, which increases hand pressures, longer rides, and lack of appropriate padding in handlebars or gloves. Frequent changes in hand position are helpful in providing pressure relief (Fig. 3).
Evaluation of the Cyclist
Effective rehabilitation of the cyclist involves identification and correction of contributing biomechanical factors in both the cyclist and the bicycle. In our Cycling Medicine Clinic, evaluation of the cyclist begins with a detailed history of the injury or discomfort and presence of symptoms off the bike, on the bike, or both. There must be inquiry regarding cycling activities, such as climbing, sprinting, long distances, or specific gears, which provoke symptoms. Degenerative joint disease or spondylosis can affect the cyclist’s mechanics and may require accommodations on the bicycle. A full cycling history also should include the athlete’s disciplines of cycling, training, and racing schedule, cross-training, as well as prior crashes, injuries, and treatments. For athletes with neurologic symptoms, questions regarding head injury and a brief concussion screen may be appropriate. In our clinic, all patients are asked about helmet use, including whether their helmet is still under warranty. Prior imaging is reviewed, and for patients with complaints of fatigue or declining performance, a review of their HR and power data, if available, may be helpful.
The cycling-specific physical examination should clearly be tailored to the athlete’s complaint; however, there are certain tests that may be helpful in a number of different scenarios. The single-leg squat test is a simple and very useful in-office test for weakness or decreased recruitment of hip abductors and may show contralateral pelvic tilt or ipsilateral medial knee deviation, frequently seen in cyclists (5) and in individuals with patellofemoral or lumbar spine complaints (8,13). Assessment of lumbosacral and hamstring flexibility is useful in determining how much forward flexion an athlete is prepared to tolerate on the bicycle. For lumbar spine complaints, assessment of directional preference and dural tension (seated slump test) is often useful. Cyclists with anterior knee pain may show a positive J-sign, tenderness over the patellar facets, or positive patellar compression maneuvers. A foot and ankle examination to identify foot flexibility, ligamentous laxity, and position in weight bearing (i.e., degree of navicular drop) may illuminate a potential culprit for more proximal problems.
If available, the third part of the cycling-specific evaluation should include an assessment of the cyclist’s position and biomechanics on the bicycle. This requires relatively little in equipment, a stationary bike trainer, and a keen eye for mechanics. The physician should not double as a bike fitter without the appropriate training and certification; however, the physician should be familiar with the basic principles. A collaborative evaluation with a certified bike fitter, as is done in our Cycling Medicine Clinic, is extremely helpful in making specific recommendations regarding modifications to fit or components.
Depending on diagnosis, the plan of care may involve acute treatment to decrease pain, followed by correction of the underlying imbalances and adjustment of fit. Using the common scenario of patellofemoral pain or chondromalacia as an example, medical management may start with pain control, ice, and taping strategies. Any medications or procedures prescribed for competitive cyclists should be scrutinized to ensure compliance with the World Anti-Doping Agency guidelines (2). Medications also may be checked with the online portal http://www.globaldro.org to ensure they are not prohibited in or out of competition. Physical therapy should incorporate a focused strengthening and flexibility program for the lower extremity and hip abductors. A certified bike fitter should assess cleat position, saddle position (typically too low or anterior), and knee tracking while pedaling. The patient may need to temporarily modify their training to reduce hill climbing and incorporate lower-resistance, high-cadence cycling. In more severe cases, injection-based therapy may be useful, and in recalcitrant cases, surgical consultation may be indicated.
Beyond the physical rehabilitation, there may be fear and avoidance issues surrounding the return to cycling. Because a serious injury or crash is both physically and emotionally traumatizing, psychological factors, including fear of riding in groups or returning to racing, are frequently seen and uncommonly addressed. Advances in sports medicine have allowed athletes to return to play more quickly, which may not allow adequate time for psychological recovery. Further research is ongoing to address this issue and its impact on cyclists’ health and return to sport.
Conclusion
The evaluation and management of cycling injury is a collaborative process involving athletes, physicians, physical therapists, bike fitters, and, for some, athletes or coach. Correction of anatomical factors, technique errors, training habits, and bike fit can all improve comfort and enjoyment on the bicycle. Where the human body is limited, the machine can be adapted to the rider. A team of knowledgeable clinicians and fitters, with open communication and common language, can help athletes with nearly any injury, limitation, or disability enjoy the exhilaration and freedom of cycling.
Dr. Kotler and Dr. Babu declare no conflicts of interest and do not have any financial disclosures.
Greg Robidoux is the director of education for Serotta International Cycling Institute and cochair of Medicine of Cycling.
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