History and Classification
Adaptive cycling has rapidly evolved around the world, both recreationally and as a competitive adaptive sport. Over approximately the last two decades, competitive rules and regulations along with avenues through which adaptive cyclists may compete have grown considerably. Today, cycling is now the third largest Paralympic sport, trailing only athletics (track and field) and swimming (1). Road paracycling first premiered at the Paralympic Games in 1984 (1,2). In 1988, the Paralympics added events for cyclists with visual impairments, and in 1994, the first paracycling world championship event was held (1). By 1996, 23 different paracycling events took place at the Paralympic Games in Atlanta, including the first formal Paralympic track events (1,2). Adaptive handcycling became recognized by the International Paralympic Committee (IPC) as a form of paracycling in 1999, and finally part of the Paralympic games for the first time in 2004 in Athens (1,3). Governance of paracycling was subsequently transferred from the IPC to Union Cycliste Internationale (UCI) in February of 2007 (1,4). As of January 2020, adaptive cycling has a total of nine UCI-designated events, including three road and six track races (Table 1) (5). Key international competitions for adaptive cyclists include the World Championships, Paralympic Games, and World Cup (3).
The four main types of cycles used in adaptive cycling are handcycles, tricycles, standard upright bicycles, and tandem cycles (1,5). Only certain cycle classes compete in certain events: adaptive cyclists competing on standard bicycles and tandem cycles may compete in both road and track events, whereas those competing on handcycles and tricycles may only compete in road but not track events (1). There are 10 eligible impairment types permitted to compete in the Paralympics; however, only eight qualify for inclusion in competition for adaptive cycling: impaired muscle power, impaired passive range of movement, limb deficiency, leg length difference, athetosis, hypertonia, ataxia, and visual impairment. However, as a sports medicine provider, it is important to be aware that there are numerous noneligible impairment types of adaptive cyclists who ride for recreation and not in competition. Therefore, a sports medicine provider may encounter a recreational adaptive cyclist with other impairments to include those with intellectual impairment, short stature, pain, low muscle tone, impaired muscle endurance, hearing impairment, joint instability, impaired cardiovascular, respiratory, and/or metabolic function, and hypermobility (5,6).
Handcycling has five classes (H1 to H5) (Table 2) (5,7). The classes are numbered with the lower number having a more severe level of impairment. H1 athletes are tetraplegic (C6 or above) and generally have severe upper-limb impairment with no ability to use their trunk or legs. H2 athletes also are tetraplegic (C7/C8) with severe athetosis, ataxia, and/or dystonia. H3 athletes may have spinal cord lesions anywhere from T1 to T10 (or equivalent injury) with limited trunk stability. H4 athletes will have impairment from T11 down, with normal or almost normal trunk stability, but be unable to kneel. Those competing in classes H1 to H4 compete in a reclined position and compete on a recumbent handcycle, whereas H5 class athletes are paraplegics (T11 or below) and limb-deficient athletes who distinguish themselves from H1 to H4 by being able to kneel and compete on a kneeling handcycle. Those competing in classes H1 to H4 compete in a reclined position, whereas H5 competitors can sit on their knees and may use both their arms and trunk. Examples of H1 to H4 athletes include those with spinal cord injury, cerebral palsy, or multiple sclerosis. H5 athletes have leg amputation or congenital limb deficiency, paraplegia, or ataxia (5,7).
Tricycling has two classes (T1 to T2) (Table 2) (5,7), again with the lower number corresponding to a higher degree of impairment. Adaptive cyclists will use a tricycle if their coordination or balance is affected enough to require the tricycle for stability while riding. T1 tricyclists have severe athetosis, ataxia, or dystonia, and generally with grade 3 spasticity or higher. T2 tricyclists have more moderate athetosis, ataxia, or dystonia with more fluent movements, grade 2 spasticity for hemiplegic and quadriplegic patients, and grade 3 spasticity for diplegic athletes.
Adaptive cyclists capable of riding a traditional upright bicycle will compete in one of five classes (C1 to C5) (Table 2) (5,7), once again with lower numbers corresponding to the highest degree of impairment. C1 cyclists have grade 3 spasticity in upper and/or lower limbs with poor strength in the trunk and/or extremities or can have single- or double-limb deficiency. C2 cyclists have grade 2 spasticity throughout with greater lower limb involvement. C3 cyclists will have less spasticity in the upper limb (grade 1) versus the lower limb (grade 2), and with less athetosis, ataxia, or dystonia than C1 or C2 cyclists. C4 cyclists generally have grade 1 spasticity with the lower limb more involved and mild to moderate athetosis, ataxia, or dystonia. C5 cyclists have minimal impairment, such as monoplegia spasticity with clear neurologic signs or single amputation. Classes C1 to C4 may include athletes with a limb deficiency, whereas these athletes would not qualify for a C5 rating. Overall, athletes in the C5 classification have only minimal impairments compared to the athletes in the C1 to C4 classes. Adaptive athletes who compete with an adaptive bicycle would include those with limb deficiency, impaired muscle power or range of motion, and coordination deficits (Table 2, Fig. 2).
Tandem cyclists are visually impaired, and ride with a sighted “pilot” cyclist, typically in the front, under a single classification (B) (Table 2) (5). The role of the sighted “pilot” cyclist will be for navigation and steering with contributions to power, whereas the competing impaired athlete will be sharing in the contributions to power. The pair of cyclists must cycle in sync with each other. All visually impaired tandem cyclists typically compete together in the same event(s). Professional cyclists who are current members of a UCI registered team, or those who have competed on a UCI world and/or professional team within the last 12 months, cannot compete as a tandem pilot. This is to avoid giving the visually impaired cyclist an unfair advantage in competition. Although there is one sport class in paracycling for visually impaired athletes, the athletes are designated B1, B2, or B3 in accordance with the International Blind Sports Federation visual acuity classes. B1 cyclists effectively have no sight, B2 cyclists have a visual field constricted to a diameter of less than 10 degrees, and B3 cyclists have a visual field constricted to a diameter of less than 40 degrees (5,8).
Cycle Design and Technology
Adaptive cycles come in many different styles to accommodate various impairments and for a corresponding variety of events. Cycle types include competitive and recreational handcycles, as well as adapted tricycles and bicycles. Examples of adaptive athletes include those with limb deficiency, hemiplegia, spinal cord injury, visually impaired athletes, and those with cerebral palsy/intellectual disability. Adaptive athletes using these types of adaptive cycles include those with limb deficiency (i.e., amputation or congenital deformity), spinal cord injury (paraplegia and quadriplegia), and hemiplegia from stroke/brain injury. Visually impaired athletes and those with cerebral palsy/intellectual disability ride with sighted, tandem cyclists trained in aiding such adaptive athletes (7).
Adaptive handcycles were first designed to help impaired military veterans navigate tougher terrains after World War I and are now used more recreationally and competitively. Two designs typically used in competitive handcycling are “kneeling” and “recumbent” handcycles (Fig. 1) (9). Handcycles are more efficient than standard push-rim wheelchairs or cycles used for track racing and are more ideally driven for road racing. Road racing handcycles are usually three-wheeled and can be front-wheel or rear-wheel–drive. Compared with the racing wheelchairs or track cycles, the adaptive athlete transmits power to the wheel/axle through the drivetrain (pedals, cranks, chainrings, chain, cassette/cog, or derailleur. Handcycles are operated by the adaptive athlete using their upper limb(s) and/or torso, contingent on their disability (7).
Tricycles and bicycles for adaptive athletes typically align in design with those for able-bodied individuals; however, tailored adaptations (i.e., attachment for lower limb prosthesis to foot pedal, etc.) are then installed. Considerations include cyclist size and body/cycle interface points (i.e., the perineum contact on the seat, the hand-grip point on the handlebars, and shoe/pedal interface), which may impact how the athlete can reach the cycle components. There are a vast variety of modifications to accommodate each individual athlete and their impairment and allow the adaptive athlete to cycle (Fig. 2). The UCI regulations also only allow a standard diamond-shaped frame for upright bicycles during competition with various more aerodynamically designed frames outlawed (7,10).
Tandem cycles have two seats, one for a sighted “pilot” cyclist and another for the visually impaired cyclist. The tandem cycle has two wheels of equal diameter, with the front wheel steerable. Both riders face forward. The pilot, typically in front, controls steering, gear changing, and tactics, whereas the visually impaired cyclist must instantly react to cadence increases, as well as changes from standing to seated positions on verbal cue. The rear wheel is driven by both cyclists through a pedal and chain system. The visually impaired cyclist also must be able to remain calm and composed during sudden movements of the tandem cycle and changes in road slope or other race conditions. The tandem cycle also is ideally designed such that the sighted pilot cyclist and visually impaired cyclist are positioned as close as possible to optimize aerodynamics (5,7,10).
Saddle height, saddle setback, saddle tilt, the length of handlebar/hand control reach from the saddle, the handlebar height drop from the seat, crank length, and the saddle tube angle are important factors in cycle design and need to be optimally configured. Changes in cycle configuration influence trunk angle, which in turn influences muscle recruitment and kinesiology patterns, ultimately affecting power output and cycle speed (10).
Injuries and Medical Concerns
Adaptive cycling includes a diversity of athletes with varying disabilities, and there are an array of medical complications and injuries they may sustain. Injuries often mirror those seen commonly in able-bodied cyclists. However, there are diagnoses commonly encountered in adaptive athletes that are based on their preexisting condition.
Autonomic Syndromes, Environment, and Boosting
Patients with spinal cord injuries at the T6 level or above are at risk for autonomic dysreflexia (AD) as well as orthostatic hypotension (11). These athletes also are unable to maintain and regulate normal body temperature above the T8 level (11). Therefore, athletes with paralysis at the T8 level or above may be at increased risk for heat exhaustion or heat stroke. During competition, some adaptive cyclists also may be excessively sensitive to heat, cold, or altitude, particularly cyclists with higher-level spinal cord injuries whose autonomic function can be dysregulated. It also is important for the sports medicine provider to be aware of the race season, location, race distance, and duration when one is assessing athletes with environmental-related injuries and illnesses.
Cycling as a sport has been plagued with doping. However, in the adaptive athlete, there are concerns about a different type of doping. This doping, known as “boosting,” is a concern in spinal cord-injured athletes. These athletes try to self-induce AD (“boosting”) that could in turn enhance para-athlete performance. AD is a very potent sympathetic reflex caused by a massive release of noradrenaline (12). Boosting is often induced by bladder overdistention via ingestion of a large amount of fluid before competing (13). While this practice improves performance, it also can increase blood pressure substantially, potentially endangering the athlete's health. Deliberate attempts to boost by adaptive athletes are expressly prohibited by the IPC and, if detected, can lead to an investigation and disqualification (12). Only recently has testing for AD in handcycling competitions been implemented. They have yet to yield a positive test nor have any adaptive hand cyclists been disqualified. This potentially offers hope that testing can serve as a reliable deterrent to intentional boosting to induce AD (12,14).
Musculoskeletal, Neurologic, and Pain Syndromes
Adaptive cyclists, whether they have paralysis, hemiplegia, or limb deficiency, encounter many of the same musculoskeletal and neurologic complications as able-bodied cyclists. Adaptive cyclists may sustain injuries to their upper extremity including hands, wrist, shoulder, and elbow joints. Pain also can occur in the spine and pelvic region, as well as the lower extremities, such as the hip, knee, leg, ankle, and foot. There also may be an increased risk of compartment syndrome in the extremities of adaptive cyclists, especially if there is undue pressure from a prosthetic component or if they have difficulty moving their extremities leading to increased intracompartmental pressures and pain. If compartment syndrome is suspected, compartment pressure testing should be done as soon as possible (7).
Upper-extremity neuropathy, such as carpal tunnel syndrome or ulnar neuropathy, occurs in as many as two thirds of spinal cord patients, so even higher vigilance must be paid to adaptive cyclists in these regards (7,11). There also are other very common neurologic conditions that can be encountered in athletes with spinal cord injury to include myelopathy from syringomyelia, thoracic outlet syndrome, and spasticity (7,11).
As many SCI patients use a wheelchair for primary mobility, it is very frequent for persons with SCI to have upper-extremity issues. As many as 70% of chronic SCI patients will report pain in their upper limbs (7). Tetraplegic athletes will be at higher risk for upper-extremity pain than paraplegics. As such, it is important to have a high index of suspicion for common causes of upper-extremity pain in adaptive cyclists. The shoulder will be most affected because it is used as a weight-bearing joint, as well as for wheelchair propulsion in wheelchair athletes. Tendinitis (subacromial) bursitis, rotator cuff injury, capsulitis, myofascial pain, and cervical radiculopathy are common reasons for upper-extremity pain in these cases (7).
Heterotopic ossification (HO) often develops in those with SCI or other sedentary paraplegic/quadriplegic conditions. Therefore, the provider must be cognizant of this when evaluating adaptive athletes because they may have HO-related pain. Treatments for HO include physical therapy, modalities, dry needling, oral medications, including acetaminophen, nonsteroidal anti-inflammatory drugs, oral steroids, and bisphosphonates. It is important to be familiar with medication restrictions in and out of competition and may require the submission of a Therapeutic Use Exemptio. Physical therapy should focus on range of motion, scapular stabilization, and rotator cuff strengthening to promote stable, balanced shoulder, and upper-extremity movements, so that while cycling, the adaptive athlete has optimal posture and kinesiology. Functional electrical stimulation may be used to help conditioning and muscle bulk/strength as well. Stress or pathologic fracture also are a risk because such adaptive athletes may have decreased bone density in the setting of impaired ambulation, particularly in the athlete with a spinal cord injury (7).
For those patients with cervical spinal cord lesions, tendon transfer or nerve grafting procedures may be necessary to restore more optimal function to the upper extremity to allow better ability to control a handcycle.
Neuropathic pain, characterized more by burning, tingling, or shocking pain also can arise in such athletes and should be treated first with neuropathic agents, such as gabapentin or pregabalin, as well as tricyclics, such as nortriptyline or amitriptyline. One also may try treating neuropathic pain with anticonvulsants, such as carbamazepine, or even topicals, such as capsaicin, lidocaine, or diclofenac. Complex regional pain syndrome also can be seen in adaptive cyclists if they have a specific focal injury resulting in nerve damage (7,11).
Pudendal nerve entrapment has been more frequently seen in upright bicyclists, as well as those who use a stationary bike for exercise. This condition also is encountered in adaptive cyclists. Cyclists are at increased risk due to chronic perineal microtrauma resulting in inflammation and/or fibrosis in the pudendal canal and sacrotuberous/sacrospinous ligaments where the pudendal nerve lies (15). Treatments for pudendal nerve entrapment and nerve irritation include adjusting and/or changing the saddle as well as rider position, prescription of neuropathic agents as listed above, and image-guided pudendal nerve blocks with steroid and/or anesthetic.
Adaptive cyclists with spinal cord injury will commonly present with neurogenic bowel and bladder. These athletes typically already have interventions in place (i.e., suprapubic catheter, bowel program), and there is a potential that adaptations need to be made to the athlete's cycle to accommodate them. Neurogenic bowel and/or bladder dysfunction may occur by dysregulation and/or injury to both central and peripheral neural pathways that can affect innervation to the gastrointestinal tract and/or bladder (11).
Unfortunately, as noted previously, there exists a controversy with regard to “boosting” in Paralympic athletes in which adaptive cyclists intentionally avoid emptying their bladder to creating overdistention to activate AD. There also are athletes who will purposefully alter their bowel program to create bowel distention for a similar purpose. This doping method, previously noted as “boosting,” increases the sympathetic response just prior to competition, resulting in a noradrenaline surge (12,14). It is beneficial for the sports medicine provider covering adaptive racing to be aware of this potential practice, because AD can be a serious and deadly complication (12).
Sedentary or impaired individuals are commonly at higher risk of deep vein thrombosis or pulmonary embolism, and this is of concern in paraplegic/tetraplegic athletes. Adaptive cyclists also can have (exercise induced) asthma requiring intermittent or chronic treatments, including inhalers and nebulizers, as well as rescue inhalers available. Limb-deficient athletes are known to have higher-energy consumption than able-bodied athletes so cardiopulmonary demand in those cyclists also are higher (7,11). Arrhythmias, coronary artery disease, and heart failure can be seen in adaptive cyclists with associated physical decompensation. Adaptive cyclists also may have peripheral vascular disease resulting in claudication and decreased functionality of their extremities (7,11).
Dermatologic and Skin Conditions
Careful attention should be paid to areas where an adaptive cyclist may place excess pressure or friction while cycling leading to weight bearing and/or overuse injuries. In cycling, the gluteal and buttock regions could be unusually susceptible to pressure ulcers or friction abrasions, depending on positioning and stress while cycling. The upper and lower extremities also could be susceptible to blisters and friction abrasion. Areas of increased pressure on the body of adaptive cyclists can be niduses for skin breakdown, infection, and systemic disease. Particularly regarding athletes with paraplegia or tetraplegia from spinal cord injury, it is important to be vigilant about skin care in these athletes. The adaptive cyclist may or may not have sensation, depending on whether they have a spinal cord lesion and the location. The athlete's decreased sensation could decrease awareness by the athlete regarding skin breakdown. Lacerations, pressure ulcers, rashes, and callous formation could all lead to skin breakdown in the sensate or insensate athlete, particularly at the seat of the cycle where there would be prolonged pressure on bony prominences (i.e., the ischial tuberosity) where the athlete sits (7,11).
Dermatologic conditions also are of heightened importance in limb-deficient athletes: folliculitis, boils, abscesses, verrucous hyperplasia, lichinification, tinea corporis and cruris, epidermoid cysts, contact/allergic dermatitis, and excessive sweating can lead to skin lesions, infection, and further systemic complications if not controlled. Verrucous hyperplasia is the development of “warty” verrucous plaques that develop over the distal limb of an amputation. Lichinification is the development of a leathery appearance of the skin in the residual limb. The pathophysiology of these complications is due to a poor fitting prosthesis, suction socket prosthesis, venous stasis, excessive sweating, and friction (7,11).
For any open or exposed wounds, traditional wound healing measures would include cleaning and irrigating the affected area (usually with isotonic saline) and applying the appropriate dressing. It also would be beneficial in taking antibiotics if there is suspicion for bacterial infection. Vitamin supplements (multivitamin, zinc, vitamin C, copper, arginine) may be taken for severe cases. Also, if the wound fails to heal by conservative measures a wound vacuum and/or surgical intervention may be necessary (7,11).
Diabetes or thyroid disease could affect neurologic function and/or cause skin breakdown in adaptive cyclists. Adaptive cyclists with decreased mobility could have decreased bone density and osteoporosis. In these regards, vitamin D and calcium levels should be monitored and appropriate patients sent for bone density scans to assess the degree of bone loss. Adaptive cyclists with traumatic brain injury also may suffer from hypopituitarism/hypogonadism which in turn can promote osteoporosis (7,16).
Hand cyclists with spinal cord injury, amputations, traumatic brain injury, or other impairments are already facing psychological challenges intrinsically associated with their impairment(s). Engaging in adaptive handcycling can help such athletes cope in these regards. Simultaneously, they also are susceptible to any range of depression, anxiety (posttraumatic), stress, or other emotional dilemma (possibly preexisting prior to their impairment) that could require counseling or management with psychotropic medications. A psychiatrist should be consulted for any adaptive cyclist with suicidal ideation, psychotic features, or lack of response to multiple psychotropic medications. Also, adaptive cyclists may require intervention by a sports psychologist just as an able-bodied athlete would (7,11).
Globally embraced and experiencing rising popularity, adaptive cycling continues to see a rise in athletes participating both recreationally and in formal competition. The emergence of adaptive cycling has allowed men, women, and children with various disabilities to discover a new arena for athletic activity, capable of improving their physical, emotional, and cognitive well-being. More research and study are needed to better understand the medical and technological needs of these athletes and how to provide adaptive cyclists with the best support possible.