Shoes in sports could be considered a modern phenomenon. Photographs from the first modern Olympic Games in 1896 show participants running barefoot. More recent barefoot athletes include Ethiopian runner Abebe Bikila, who won gold in Rome during the 1960 Olympic Games. Barefoot sports seem to have a surprisingly low number of injuries, sometimes even lower than the rates for athletes wearing shoes and doing the same or similar activities.
Even today, subsets of athletes believe barefoot running is the only way to train and compete. Advocates hypothesize that modern athletic footwear allows perceived impact to be lower than actual impact, which can result in injury. Others surmise that shoes decrease foot pain from poor technique, which leads to more serious injury by perpetuating poor mechanics. In either case, problems can then become disseminated along the kinetic chain.
Do barefoot athletes have an advantage over their shod counterparts? Observations of populations who run barefoot or are barefoot habitually point to lower injury rates versus the shod population, but prospective studies and randomized controlled trials are lacking (26).
So what then are the differences in shod and barefoot running? Numerous recent studies have sought to address this question and sort out the biomechanical differences that may lead to increases or decreases in injury rates. Results show that going barefoot may not be all that bad. Runners who have developed stride patterns that incorporate low levels of impact force and rapid pronation are at reduced risk for overuse running injuries (15). One study making a mechanical comparison found that barefoot running did lead to a reduction of impact peak with reduced mechanical stress and enhanced ankle extensor function (9). Although pronation can be protective, excessive pronation can lead to increased injury, including but not limited to first metatarsophalangeal joint (MTPJ) abnormalities, medial arch and plantar fascia strain, Achilles and tibialis posterior tendinopathy, patellofemoral joint dysfunction, and stress fractures (8). Another study produced results demonstrating that shod running decreased torsion and increased pronation significantly. These researchers surmised that the reduction of torsional movement due to stiff shoe soles could be a reason for running injuries caused by excessive pronation (32). Another study showed that peak load at hip and knee joints in participants with osteoarthritis was decreased significantly in barefoot walkers (30). These data support the concept that shoes may be increasing loads in poor physiologic patterns and perpetuating injury.
Shoe manufacturers recently have begun making and marketing shoes that mimic barefoot running. These shoes have no support and minimal cushion. They tout better feel, control, and natural motion, which they claim will produce stronger feet and decrease injury rates. Research is underway to assess the utility of these products.
Runners are prone to a multitude of foot and ankle injuries, from stress fractures and ankle sprains to plantar fasciitis. There is much more work to do sorting out the advantages and disadvantages of running barefoot, but there are a number of sports in which footwear is not an option. There are the more traditional barefoot sports like gymnastics, swimming, and diving. There are both traditional and newer mixed martial arts, and outdoor sports seem to have become more popular with beach volleyball and water sport participants dramatically increasing in number in recent years.
Surfing, windsurfing, kitesurfing, paddleboarding, bodyboarding, and skimboarding are a few of the boardsports that recently have seen a large number of new participants. While most of these are done barefoot, some boards require footstraps or foot booties, depending on conditions, although most athletes forgo the latter as they feel it impairs the "water feel" of the board. For surfing, the grandparent of all boardsports, quick and explosive movements are required, and improvements in design are increasing the speed and agility of the boards and the demands on the athlete. Injury rates reported in boardsports and surfing are conflicting. It is difficult to control for all conditions that may affect these results - wave size, crowd size (number of other surfers in the water), experience, type of board used, and environment, including vicinity to rocks and reefs. Head and lower extremity injuries usually predominate. Retrospective studies of hospitalized patients who were injured while surfing report 34% of surfing injuries to involve the craniosacral axis (2). However, increased percentages of chronic and acute injuries to lower limbs were reported in retrospective studies using questionnaires. In one study, questionnaires distributed to surfers who presented acutely to clinics or emergency departments reported numerous different types of lower extremity injuries, including lacerations, strains, and sprains, along with marine animal stings (27). In a second study, surveys were distributed to more than 600 surfers, and they were asked to recount injuries sustained during the previous 12 months. Acute foot and ankle injuries reported by surfers were close to 18% of total injuries reported. Foot and ankle injuries that were reported by surfers and managed in an emergency department were close to 13% of all injuries. Lacerations accounted for 46% of all injuries, sprains 28%, and fractures 9% (33).
Lacerations to the foot and ankle can be from the ocean floor or beach, but most often are from contact with the surfer's own board. Some have postulated that increased leash length, blunting the nose of the board, or fitting the board with a nose guard may help prevent this. The demands of surfing make acute ankle injuries a possibility. The drop at takeoff or standing up on a fast steep wave can force the surfer's feet to leave the board, causing an off center landing. This can cause excessive rotational or medial and lateral force on the ankles (13).
While ankle dorsiflexion and extensor foot mechanisms are important in surfing stance, these can lead to injury in boardsports in which footstraps are used. In fact, one study reported that 36.5% of all injuries in windsurfers were to their feet, with bruises and wounds being most common (21). Another investigation found that the most common injuries to lower leg were ligament rupture as well as lacerations, contusions, and muscle strains (24). Case reports place windsurfers at increased risk for tendonitis of the extensor digitorum longus tendon, especially if they favor the footstrap at the MTPJ level where ankle dorsiflexion movement and toe extensors are responsible for reaction forces. If the strap is moved to the midfoot level, ankle dorsiflexion predominates. MTPJ placement is preferred by athletes because of better board control, but this places continuous compressive forces on the toe extensor tendons as well as tensile longitudinal stresses that can lead to tendonitis (14). Stretching ankle dorsiflexors and rehabilitation focusing on ankle stability and proprioception would benefit boardsport athletes for both the prevention and treatment of injuries.
Kitesurfing involves an athlete using a small board and large maneuverable kite to generate speed and lift. The most common injury site for this sport is the foot and ankle (23). The most common injury types are contusions, abrasions, lacerations, and joint sprains. Most of these are the result of an athlete kitesurfing in water that is too shallow, or the kite pulling the athlete against an obstacle after the athlete loses control of the kite or when landing from a jump. Risk of injury also increased during competition. Injuries can be prevented by ensuring an athlete is kitesurfing in deep water and at a safe distance from the beach, and using a kite system that enables the athlete to release the kite. Kite leashes should be encouraged; this allows the kite to collapse should the athlete lose the handlebar. Additionally, board leashes are useful for inexperienced surfers, but this increases the trauma kitesurfers sustain from their own boards.
Skimboarding is a beachside sport that also is gaining popularity. It involves a small board with no ventral fin. The skimboarder stands on land, runs to the water, drops the board on the ground, and rides on the board across a thin layer of water at the waters edge. Alternatively they may ride waves as they break on the beach. This is referred to as sand skimming or wave skimming, respectively. Injury happens when the trajectory of the board is out of sync with the rider. In one retrospective study (N = 61), 41% of skimboarding injuries referred for orthopedic evaluation were at the ankle; over 90% of these were fractures. Rotation about a planted lower extremity was the most common mechanism of injury (29). Another retrospective study of emergency department records (N = 79) reported 63% of injuries to be fractures in the lower extremity; 83% of these were ankle fractures (20). Rare cases of "skimboarder's toe" have been reported. This is caused by hyperdorsiflexion of the MTPJ, which results in hyperdorsiflexion of the extensor hallucis longus or extensor digitorum longus tendon, and subsequent tearing of the extensor expansion. The extensor expansion consists of a band of circumferential fibrous tissue that passes around the extensor hallucis longus tendon and helps hold it in place. While the mechanism is similar to that of turf toe, the skimboarder's toe injury occurs on the dorsal aspect of the toe, while turf toe involves injury to the plantar aspect of the joint (10). These cases were treated conservatively with relative rest. There was improvement, but symptoms persisted at 6 and 9 months.
The most common injury in gymnastics remains the ankle sprain. Lower extremity injuries usually result from landing and dismounting at the end of gymnastic routines (18). Gymnasts are susceptible to both traumatic and overuse injuries; their injuries range from strained and pulled muscles to dislocations and injuries to bone, although one must be suspicious of symptoms of common ailments - they could hide more serious injuries. If a presumed ankle sprain has not responded to appropriate rest and rehabilitation, reevaluation is warranted. Plain radiographs, bone scan, computed tomography (CT), magnetic resonance imaging (MRI), and even arthroscopy can be indicated in workup and treatment of a possible osteochondral defect (OCD). An OCD of the talar dome most commonly is caused by "landing short," which forces the ankle into extreme dorsiflexion and causes the tibia and talar dome to become compressed (8).
The most common cause of heel pain in athletes is plantar fasciitis, although in gymnastics where repetitive bounding is part of the training regimen, calcaneal stress fracture also must be considered. Retrocalcaneal bursitis, Achilles tendonitis, subtalar synovitis, or plantar nerve entrapment are other possibilities (11). Barefoot athletes may be at increased risk for nerve entrapment, given that they are subjected to increased foot trauma, which may result in more scar tissue and perineurofibrosis.
SWIMMING AND DIVING
Diving is related closely to gymnastics. The complexity of both platform and springboard diving has increased rapidly over the past 100 yr. The distinction must be made between recreational and competitive diving. Medical literature on recreational diving reports head and neck injuries. Competitive diving injuries are much different. Injuries incurred to the foot and ankle during the three dive phases differ. On takeoff, posterior tibial and Achilles tendinosis secondary to eccentric overload, impact, and overtraining have been reported, in addition to ankle and foot sprains. During flight, the diver is at risk for striking the board or platform, resulting in contusion, lacerations, or fractures of the metatarsals and phalanges. Most diving injuries occur upon entry, but the lower extremity is not under high stress or impact during this phase. Foot and ankle injuries more commonly are associated with dives done in the pike rather than in the tuck position, and with reverse take-offs (28).
Swimming injuries to the foot and ankle are rare. A study of collegiate swimmers over 7 yr failed to find any injuries of the foot and ankle related to swimming (19). Explosive movement is required for starts and turns, and these subject the foot and ankle to significant force. Achilles injury may be a possibility, as with most strenuous forms of physical activity. Additionally, contusion to the ankle or foot may occur with a misplaced foot during a flip turn.
The sport of volleyball allows for a unique comparison in that it is contested at the elite level by athletes in shoes on hard surfaces indoors and barefoot in the sand. Overall injury rates actually have been found to be fourfold lower during competition on the sand compared with indoors (1,3,5). This may be related more to landing on a softer surface than to whether the athlete is shod. In particular, ankle sprains have been shown to occur less frequently in beach volleyball than indoors (3). An important factor here may be that beach volleyball is generally contested with two players per side at the elite levels that have been studied (3,5). The most common mechanism of ankle sprain is inversion when a blocker lands on the foot of an attacker (spiker) whose foot has come under the net. With fewer players on the court, there are fewer potential blockers on any given play, which may reduce the inherent risk of ankle injury.
Beach volleyball actually has a much more liberal center line rule than indoor volleyball. Indoors, a players foot may come in contact with the center line beneath the net, and may even cross this line, as long as some contact is maintained with the line. The player is only called for a foul if his or her foot has crossed completely over the line. Some data suggest that this rule is what puts blockers at risk for ankle sprain (25). However, on the beach there can be no center line. A player may go completely under the net as long as he or she does not make contact with an opponent and interfere with their attempt to play the ball. Nonetheless, ankle sprains are less common on the sand (3,5), so perhaps the softer surface is a more important variable in ankle sprain injury risk than the center line rule.
Lacerations and abrasions to the skin on the foot are another category of injury that is unique to barefoot sports that are played outdoors. (3) Such injuries typically occur in beach volleyball when a players foot comes in contact with a hard or sharp object in the sand, such as broken glass. It should be obvious that these injuries at least potentially are preventable. A reasonable recommendation to beach volleyball tournament organizers is to pay careful attention to sand hygiene before each event.
Competing on a compliant sand surface in bare feet is a combination of risk factors that can result in a rare foot injury felt to be unique to beach volleyball. This is known among clinicians who care for beach players as "sand toe." The mechanism of this injury is a hyperplantarflexion sprain of the great toe MTPJ (12). This can occur if a player steps down awkwardly into the sand, then shifts his or her weight forward. The toe then "catches" in the sand, forcing the great toe underneath the foot. This stresses the superior (dorsal) capsule of the MTPJ, which gets sprained. This usually happens when playing defense; the weight is shifted to play a ball that has been tipped in an unanticipated direction. This injury essentially is the opposite of the turf toe, seen in American football players when they hyperdorsiflex the great toe MTPJ on an artificial turf surface. The diagnosis is made clinically, when a patient with a typical injury mechanism is noted to have tenderness at the dorsum of the MTPJ capsule and pain in this same area with great toe plantarflexion. Pain typically is worse with passive plantarflexion. Active or resisted dorsiflexion is not as painful, and dorsiflexion strength typically is intact. X-ray evaluation can be considered initially to rule out fracture. MRI evaluation should be reserved for situations where surgical correction may be indicated, usually if after 4-6 months of conservative management there has been no improvement in symptoms. The severity of this injury varies. Some players are able to continue playing, often with supportive taping, while others may be out of competition for as long as 6 months (12). Taping typically is continued for the remainder of that competitive season, or until the toe can be plantarflexed passively and fully without pain. Unfortunately, there are limited data on sand toe from which to make evidence-based recommendations regarding management. Other diagnostic possibilities might be extensor hallucis longus (EHL) rupture or subluxation. If there is no dorsiflexion strength, then refer for surgical EHL repair. Rupture of the dorsal hood resulting in EHL subluxation also may result in pain most prominent with resisted dorsiflexion and dorsiflexion weakness. This also may need surgical repair.
Even though ankle and foot injuries seem to be less frequent on the sand, these injuries do occur. There also are many elite beach players who have previously played indoors and may have suffered ankle sprains in the gym. Ankle rehabilitation is similar for indoor and beach athletes. The important focus is on neuromuscular retraining, using closed chain balance and strengthening exercises. Such a program results in the ankle everters firing more quickly and with greater force to resist inversion. Daily rehabilitation exercises for a total of 8 wk may decrease the ankle injury risk almost to the same level as that for an ankle that has never been sprained (25). Even for indoor players, this rehabilitation is best done barefoot. Beach players will probably benefit most if they do some portion of their rehabilitation on the uneven sand surface, since this is the surface on which they will be returning to play.
A final risk factor for ankle sprain on the beach is worthy of mention. A player who lands on a volleyball after jumping is likely to suffer an inversion injury, irrespective of footwear or playing surface. In practice and warm-up, frequently there are balls strewn about the court. Players and coaches should be instructed to take special care to be certain that no balls roll under the feet of hitters or blockers. If this does occur during competition or training, players should be coached to yell "Ball on!" or "Don't jump!" in order to protect their teammates.
Each martial arts discipline has a significantly different distribution of injuries. Martial arts appear to be safe for young athletes, particularly those at beginner or intermediate levels (34). The risk of injury from martial arts is low compared with other contact sports. Most injuries are to the limbs and are usually mild to moderate (16). Strains, sprains, and contusions or bruising are some of the more common injuries associated with practicing martial arts. Strains can occur in both muscles and tendons and are caused by sudden and extreme force (6).
The foot receives approximately 18% of the injuries in tae kwon do, usually during sparring. The toes are easily jammed, resulting in contusion, dislocation, or fracture (7). Metatarsalgia and metatarsal fractures can result from kicks, jumps, and sparring (4,31).
Injuries to ankles occur less commonly, although martial arts movements such as the stand and kick, step and punch, turn and throw, and shuffle and lunge may place the ankle at risk. The lateral malleoli are susceptible to contusion. Ankle sprains also are a relatively common occurrence and involve inversion injury to the lateral ankle ligaments as the participant bears weight on the outer edge of the foot. These ligaments also can be injured by striking the heel hard enough to push the foot into plantarflexion. This is referred to as "heel kicking" the floor as you land to break a fall, or by landing on an opponents foot. Forces that can sprain ankles also can break bones and injure hyaline cartilage within the ankle joint, foot, and the lower leg. As previously mentioned, it is best to treat all ankle sprains with a rehabilitation program; retraining the ankle muscles and enhancing proprioception will prevent future sprains. Novice martial arts practitioners often are afflicted with Achilles tendinosis secondary to overenthusiastic application of the various stances in the end range of dorsiflexion (7).
The various martial arts fall into one of two categories: percussive and nonpercussive. In percussive martial arts, such as karate and tae kwon do, physical strikes are made with the hands, feet, elbows, knees, and head. Nonpercussive martial arts involve movements that avoid physical strikes and rely on neutralizing the opponent by throwing and locking. Examples of nonpercussive techniques include judo and aikido. Percussive styles place the feet and toes at higher risk for injury, although injuries occur with nonpercussive techniques as well. For example, fractures result from entangled toes during full power judo throws (31).
Turf toe is possible in martial arts, most frequently tae kwon do, and sprains of the great toe are common to anyone training on cushioned mats. Originally named after the artificial turf injury experienced by U.S. football players, turf toe occurs when the first MTPJ is forced into dorsiflexion. Forced dorsiflexion can occur when toes are on the mat and an athlete drops to one knee during a throw. This forced motion causes injury to the plantar capsule and ligament of the first MTPJ. The athlete will complain of localized swelling and tenderness at the first MTPJ. Imaging is indicated if the injury was associated with a pop or if there is significant swelling and ecchymosis. Plain radiographs usually are negative unless there is a small avulsion or loose body. Additionally, one should look for proximal migration of the sesamoid bones. Imaging may need to be repeated as this is sometimes a late finding and may indicate a more severe injury, such as complete rupture of the plantar plate. If suspicion is high and an x-ray is negative, an MRI may be warranted. Most cases respond well to conservative management, which consists of ice, nonsteroidal antiinflammatories, and relative rest. Taping or a stiff soled shoe can be used to protect the injured area. Recovery usually takes 3-4 wk. More severe cases may require surgery. Chronic complications include the development of a hallux limitus, which results in restricted motion at the first MTPJ. In this case, cortisone injection, physical therapy, and surgery may be indicated (22). The interphalangeal joint also can be sprained, usually from a snagging mechanism like catching the toe on a soft mat and resultant forced plantarflexion (7).
Fractures of bones of the toes or feet can occur with any severe impact or prying motion. Foot pain that results in persistent swelling or that remains painful for several days to 1 wk should prompt consideration of radiologic evaluation (17).
Toenail avulsions and subungual hematomas can occur from direct or glancing nail hits. Hematomas are treated by creating a small hole in the nail to facilitate draining. Removal of the nail may be performed if the nail itself is disrupted.
Tendon sheath trauma on the dorsal aspect of the foot can occur with inadvertent trauma, such as kicking of an elbow or equipment buckle. The extensor retinaculum may become pinched and can rapidly swell and make ambulation painful. "Conditioning" or hardening of the skin over tendons and tendon sheaths is possible. This usually is done by striking bags or buckets filled with sand or beads. Padded surfaces may be used as well. Carefully practicing kick placement may be useful to prevent this injury (31).
A martial artist must be capable of exerting tremendous forces to perform kicking, punching, and blocking maneuvers. Strengthening the trunk and extremities improves the capacity to safely exert and absorb such forces (31). Lower extremity strengthening should consist of both closed kinetic chain (e.g., squats) and open kinetic chain exercises (e.g., isolated knee extension) to prepare for closed kinetic chain (e.g., stance leg) and open kinetic chain (e.g., kicking) activities. The lower extremity resistance-training program should include exercises for the hip flexors, hip abductors/adductors, hip extensors, quadriceps, hamstrings gluteus maximus, and the gastrocnemius-soleus complex (31).
FOOT AND ANKLE DERMATOLOGY
Dermatologic concerns in barefoot sports deserve to be mentioned. The absence of footwear places athletes at increased risk for lacerations, stings and bites, and contagious skin maladies such as plantar warts or fungal infections. However, without footwear, athletes are less prone to corns and calluses, which form from excess friction, and there is a decreased incidence of ingrown toenails and hammertoe, which can be the result of poorly fitting shoes.
Foot and ankle injuries in the barefoot sports are thankfully rare. In fact, there is some suggestion that barefoot activity actually may be protective from injury. In general, it makes sense to recommend that rehabilitation exercises and activities to decrease injury risk in the barefoot sports also should be done without shoes. Rapid evaluation of these injuries may help participants initiate rehabilitation in a timely fashion and allow for more rapid return to activity.
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