Sports Medicine 10 (I): 1-8. 1990 0112-1642/90/0007-0001/$04.00/0 © ADIS Press Limited All rights reserved. SPORT2293.
Running Shoes Their Relationship to Running Injuries Stephen D. Cook, Mark R. Brinker and Mahlon Poche Tulane University School of Medicine, Department of Orthopaedic Surgery, New Orleans, Louisiana, USA
It has been estimated that 25 to 40 million Americans participate in some form of running (Gudas 1980; Stanish (984) and that between 50 and 70% of them will suffer some type of runningrelated injury requiring medical treatment (Gudas 1980). Most injuries occur in the lower extremity, with the knee being the most common site of injury (Detmer 1980; Gudas 1980; James et al. 1978; Newell & Bramwell 1984; N utig 1981; Stanish 1984). Approximately 60% of running injuries result from training errors which include: rapid mileage increase, excessive interval training, excessive 'speed work' on hills, running on poor surfaces, poor flexibility training, ignoring a previous injury, failure to recognise physical limitations secondary to a biomechanical problem, excessive toe running, and old, worn or improper footwear (Johnson 1983). This review will focus on the mechanisms of injury with an emphasis on the effect of footwear. There are hundreds of models of running shoes available from dozens of manufacturers. A good running shoe must provide cushioning, support, and stability, yet maintain a reasonable degree of flexibility (Drez 1980). A poorly designed or illfitting shoe can be an underlying factor in overuse injuries. The understanding that poor shoes may contribute to running-related injuries has led manufacturers to design shoes with added stability and motion control through the use of various com-
ponents. These include last (upper shoe) design, heel counters, lacing systems, fibreglass midsole plates, and the use of combinations of materials of varying density in the midsole of the shoe (Radin et al. 1982). Thus, according to Stanish (1984), an athlete should always bring his/her footwear to a physician at the time of physical assessment to enable the physician to make a diagnosis or prescribe an appropriate orthotic device.
1. Epidemiology The number of running injuries in a population at a given point in time (prevalence) is directly related to the number of new injuries (incidence) [Powell et al. 1986]. Kaplan et al. (1982) observed that the incidence of annual running injuries per 100 runners increased linearly with increasing distance run per week. This work supports that of Pollock et al. (1977), who earlier concluded that the frequency and duration of training are related to the likelihood of injury. Training errors contribute to acute and chronic musculoskeletal pain and disability of runners, as well as metabolic abnormalities such as anaemia, amenorrhoea, and hyperthermia. Other causes of running injuries include hazards such as dog bites and collisions with vehicles (Kaplan et a1. 1982). These, of course, cannot always be controlled by the runner.
Powell et al. (1986) suggest that age, gender, speed and body build are not important predictors of running injuries. Several authors have suggested that biomechanical abnormalities are closely related to running injuries (Brody 1980; Clement et al. 1981; Grana & Coniglione 1985; James et al. 1978; Lutter 1980; Newell & Bramwell 1984; Pinshaw et al. 1984; Taunton et al. 1982). Abnormalities that have been implicated as a predisposing factor to running injuries include leg length discrepancy, genu valgum, genu varum, genu recurvatum, high riding patella (patella alta), pes cavus, pes planus, and structural abnormalities of the toes. New runners may experience significantly greater injuries than experienced runners because their tissues are weak and untrained (Clement et al. 1981) and because they have poor running technique (Glick & Katch 1970). A history of a previous injury appears to be a risk factor for the development of a subsequent running-related injury. An individual with a previous injury may be more likely to be reinjured because the original injury may remain, the repaired tissue may not function as well (or be less protective than) the original tissue, or the injury may not have healed completely. Runners with a previous injury are more likely to reinjure the same site (Caspersen 1985). The incidence of running injuries is associated with the distance run per week. While the rate of injury is higher among runners who run a greater distance per week (Blair 1985; Kaplan et al. 1982; Pollock et al. 1977), Kaplan et al. (1982) have suggested that the risk of injury per kilometre actually decreases as weekly distance increases. Therefore, those who run further are not necessarily more likely to be injured (Caspersen 1985). The stability of running habits seems to have a tremendous impact on running injuries. Along with anatomical factors, a sudden change in weekly distance or training habits has been implicated as a significant cause of running injuries (Brody 1980; Clement et al. 1981; Grana & Coniglione 1985; James et al. 1978; Lutter 1980; Newell & Bramwell 1984; Paglia & Jackson 1980; Paty & Swafford 1983; Taunton et al. 1982). Gradual changes, such as slowly
Sports Medicine 10 (1) 1990
increasing the distance of a jog, allow the body to adapt physiologically. An abrupt increase in stress on the musculoskeletal system is likely to produce an injury. The amount of stress needed to elevate the risk of injury is unknown; but the Guidance from Stress on Running (Henderson 1977) suggests that weekly mileage should not be increased by more than 10% per week. Poor running technique is another cause of running injuries (Brody 1980; James & Brubaker 1972) but is a complex matter since each unique technique leads to different stresses on a variety of the tissues. Stretching has been recommended as a method of reducing the incidence of running injuries, presumably by increasing the range of motion around the joints and, thereby, reducing the stress placed on the tissues around the joints during running (James et al. 1978; Shellock & Prentice 1985). A recent study by Blair (1985) found no association between stretching habits and the incidence of injury. Similarly, warming up has been recommended to reduce the incidence of musculoskeletal injury by improving muscle elasticity and joint range of motion (Shellock & Prentice 1985). Several reports, however, have suggested that those who warm up prior to running are more likely to sustain an injury than those who do not warm up (Kaplan et al. 1982). Offseason and inseason weight training programmes have been implemented to increase quadriceps strength. Weight-training has been advocated as a means of providing greater support and stability to the joints and surrounding tissues (Stanish 1984), especially the knee, in the hope of reducing injuries. Running up or down hills has been reported to produce inj ury (Brody 1980; Clement et al. 1981; James et al. 1978; Kirby & Valmassy 1983; Newell & Bramwell 1984; Pagliano & Jackson 1980; Taunton et al. 1982), but a confounding report by Blair (1985) suggests that no association exists between terrain and rate of running injury. It also has been suggested that surfaces that are hard or uneven cause more injury than soft or level surfaces (Brody 1980; Clement et al. 1981 ; James et al. 1978; Kirby & Val massy 1983; Pagliano & Jackson 1980), but Blair (1985) found no difference in the incidence
Running Shoes and Running Injuries
of injury between those who usually ran on an artificial surface and those who usually ran on the street. A recent study has suggested that morning runners are more likely to be injured than those who run at other times (Pagliano & Jackson 1980). Again, however, Blair (1985) found no association between time of day and running injuries. Finally, shoes without cushioning, support, or stability have been implicated as a cause of running injuries (Brody 1980; James et al. 1978; Newell & Bramwell 1984; Taunton et al. 1982).
joint, which works in harmony with the subtalar joint. The subtalar joint loosens the foot, and the midtarsal joint tightens it and supports the arch. Neutral position of the subtalar joint is the most advantageous because it is the position where the foot functions most efficiently with the least amount of stress on the joints, ligaments, and tendons (Drez 1980). Overpronation destroys the relationship of the 2 foot joints and the midtarsal joint does not have time to tighten the foot before propulsion (the final phase of the running gait) and a floppy foot results (Ellis 1985).
2. The Running Cycle 3. Running Shoes A clear understanding of injuries related to running may be achieved if the biomechanics of the running cycle are examined. The running cycle may be broken into the support phase and the recovery phases. The support phase is broken into foot strike, midstance, and propulsion (take-oft) [Root et al. 1972]. Foot strike (heel strike) is the most critical stage of the running gait and has been shown to generate 2 to 3 times normal bodweight (Cavanagh & LaFortune 1980; Miller 1978). The first shock is absorbed as the foot makes contact with the surface. It has been suggested that the crucial pressure to the body is at the calcaneus, which accounts for most of the energy transfer (Misevich & Cavanagh 1982). A shock wave travelling in bone on heel strike has been reported by several authors as vibrations from 25 to 100Hz (Munro et al. 1975; Paul et al. 1978; Voloshin & Wosk 1980). These shock waves travel up the axial skeleton and are attenuated along the way, and their transmission through the skeletal system may playa role in various acute and chronic injury mechanisms (Dickinson et al. 1985). The second part of the shock phase deals with pronation which is essential for heel strike. Pronation is the runner's adaptive attempt to create better shock absorption. Pronation is present throughout 70% of the support phase (Drez 1980). Supination is present throughout 75% of the cycle (when the foot is airborne). During midstance the foot accepts all bodyweight and the arch does most of its work. During midstance, the arch is controlled by the midtarsal
Shock absorption and control and stabilisation are important running shoe design parameters (Bates et al. 1980). The running shoe support contends with 2 important impulse variables which must be tailored to the natural running cycle. First, the maximum vertical force related to the shoe's ability to absorb shock at impact and at forefoot loading. The average force is a composite rating of the shoe's ability to protect the foot from these 2 force components, which results in 85% of the total impulse applied to the foot during each step. Additionally, the medial-lateral force relates to the shoe's overall ability to control the foot and provide a stable base in the direction perpendicular to the path of motion. State of the art motion-control shoes are designed to limit overpronation, not eliminate all inward rotation (Ellis 1985). This is accomplished by the shoe's overall ability to control the foot and provide a stable base in the direction perpendicular to the path of motion. Support can be achieved by a heel counter structure (Bates et al. 1980). Overpronation leads to knee problems due to the knee's low capacity to absorb torsion (Ellis 1985). During running, each foot strikes the ground approximately 500 times/km. Each foot (of a 70kg man) receives approximately 70 tonnes offorce per kilometre while running. A good training shoe must provide cushioning, support, and stability, and must maintain reasonable flexibility, softness, and lightness. The shoe consists of the outsole, midsole,
wedge, insole, heel counter, quarterlining, heel counter support, upper (last), sockliner, ankle collar, heel tab, and lacing system. The outer sole is generally composed of a carbon rubber material with radial tyre-Iike toughness bars or studs for traction. Studs generally provide better traction on dirt surfaces, while low profile bars tend to wear longer on hard surfaces. The outer sole provides flexibility, durability, and shock absorption. The midsole of a shoe is located along the length of the outsole between the wedge and insole. The wedge begins at the metatarsal area and extends back to the heel and is considered a part of the midsole. The material that is used to construct the wedge and midsole of the shoe is ideally designed for shock absorption with a short memory after compression. This allows the midsole to rebound in preparation for each subsequent footstrike. This material is usually comprised of 2 or 3 different foam materials [either ethylene vinyl acetate (EVA) and/or polyurethane] of varying density. Because polyurethane is more expensive than EVA, shoes with this midsole are typically more costly than a shoe's midsole constructed with EVA. The midsole functions to absorb most of the shock during running. The insole is located in a position overlying the midsole. The wedge is designed for shock absorption and comfort. The heel counter must be firm in order to help stabilise the foot and prevent shoe breakdown. The heel counter is usually constructed of a stable thermoplastic and is the most important device for preventing overpronation. The quarterlining covers the heel counter. The heel counter support is another motion-control device. It supplies the heel counter with additional support in preventing roll over. The last or upper part of the shoe approximates the normal foot contour and should be tailored to prevent any minor alterations in the gait that might occur with the inflare that most shoes have built into them. The sockliner may be thought of as the skin of the inner shoe. It likely accounts for minimal shock absorption, but absorbs perspiration and prevents it from reaching the insole and wedge which pre-
Sports Medicine 10 (1) 1990
vents diminution of the shoe's overall ability to absorb shock. The ankle collar is usually heavily padded and provides comfort and fit, while the notched heel tab is padded and aids in reducing stress on the Achilles tendon. The lacing system is a vital component ofthe running shoe and supplies the final stability between foot and shoe.
4. The Role of the Running Shoe Dickinson et al. (1985) and Cavanagh (1980) have stated that running shoes reduce the initial heel spike compared with a bare foot run. The authors also have demonstrated the midfoot striking technique may eliminate the heel strike altogether. The latter may be part of the solution to many running-related injuries, because approximately 60% of running injuries are due to an error in training (Drez 1980). The magnitude of the heel strike increases as the runner becomes fatigued (Dickinson et al. 1985). Excessive wear of the sole must be avoided. This is particularly important at the outer edge of the heel because, when it occurs, imbalance results in
abnormal stresses transmitted to the foot and lower extremity during heel strike (Drez 1980). A shoe patch can prevent this. The material used to construct the midsole is the limiting factor in shoe performance and must be improved or replaced if proper long term protection is to be provided (Sohn & Micheli 1984). The ability of a shoe to retain the initial shock absorption or cushion ability decreases with increasing mileage (Cook et al. 1985). Likewise, rate of injury is higher among runners who run more miles per week (Blair 1985; Kaplan et al. 1982; Pollock et al. 1977). There is probably a relationship between decreased shock absorption of running shoes and increased mileage run per week. Mechanically-tested shoes of various brands and prices have showed no significant difference between ability to absorb shock (Cook et al. 1985). Thus, the price of shoes may not directly reflect the quality of the shoes.
Running Shoes and Running Injuries
5. Running Injuries The most common running-related complaints are knee pain, posterior tibial syndrome (shin splints), achilles tendinitis, plantar fasciitis, stress fractures, and iliotibial tract tendinitis (N utig 1981). The knee is the largest joint in the body and is one of the most vulnerable to injury (Newell & Bramwell 1984). Most overuse injuries of the knee are in and around the extensor mechanism of the knee joint which is comprised of the quadriceps complex, the patella, and the patellar tendon and its insertion onto the tibial tubercle. Muscle loading causes the patella to track in the trochlear groove during the running cycle. Weakness in the quadriceps complex and variations in patellar alignment that lead to abnormal patellar tracking are 2 of the most common causes of extensor mechanism injuries (Newell & Bramwell 1984). From midstance to takeoff, the tibia rotates externally from its internally rotated position during midstance. The foot supinates to lock the midfoot so that it acts as a lever arm for takeoff (Root et al. 1977). A shoe with a poor heel counter and heel counter support may cause overpronation and result in internal tibial or femoral torsion, which can increase the risk of injury. Patellar pain is quite common in runners and is caused by retinacular strains, synovitis and irritation of intrasynovial plicas (Newell & Bramwell 1984). Posterior tibial compartment syndrome (shin splints) is the most common injury of the lower leg (Johnson 1983). It is characterised by pain in the medial lower two-thirds of the skin adjacent to the tibia. The pain initially occurs after a run or jog, but as the problem progresses, it occurs while running. Posterior tibial syndrome is seen more commonly in the ill-conditioned athlete (Andrish et al. 1974), but is rarely seen in the well-conditioned athlete (Detmer 1980). Posterior tibial syndrome is typically caused by running on hard surfaces or inadequate arch support, flat feet, or from excessive foot pronation. Pronation can be caused by running on banked surfaces and/or wearing running shoes that have improper shock absorption properties (Johnson 1983). A short period of rest for
the recreational runner with shin splints is a good treatment. Additionally, proper shoes, stretching, appropriate conditioning, and workouts on softer surfaces will prevent most recurrences (Detmer 1980). Achilles tendinitis is a common injury of the foot (Johnson 1983). Athletes complain of burning pain and swelling in the Achilles tendon area during the initial stages of running. Pain typically increases after exercise and increases after awakening. The causes of achilles tendinitis include running, the use of shoes with rigid soles, poor gastrocnemius-soleus flexibility, and excessive foot pronation. Most shoes are now built with a slightly raised heel which serve to eliminate overstretching the Achilles tendon (N utig 1981). Plantar fasciitis is the most common cause of heel pain (Ellis 1985). This injury is associated with excessive pronation of the foot while running, and the presence of 'flat feet' or feet with very high arches. The plantar fascia is stretched when the foot is flattened, resulting in pain. Pain occurs on the medial side of the calcaneus and radiates toward the toe. Pain is felt at the beginning of the run, but diminishes during the course of the run. The problem continues on a day-to-day basis and from training sessions. With time, an osteophyte or bone spur may arise at the insertion of the plantar fascia on the calcaneus. A shoe with poor or no arch support may allow the plantar aponeurosis to stretch and produce pain in a runner and result in plantar fasciitis. The condition of stress fractures was first described in the early 1900s by military physicians (Nitz & Scoville 1980). Stress fractures of running have been documented in virtually every bone in the lower extremity and pelvis (Blair 1980; Daffner 1982; Drez 1980; Editorial 1971; Latshaw et al. 1981; Schlefman 1981) with the tibia being the most common site (Sullivan et al. 1983). The mechanism of this injury was first described by Devas and Sweetnam (1956) who stated that stress fractures of the fibula in athletes most commonly arise from running on hard surfaces. Brahms et al. (1980) have suggested that the muscular system provides shock absorption, and when the system becomes fa-
Sports Medicine 10 (1) 1990
tigued, it loses its efficiency and allows the biomechanical forces to be transmitted to the bone more readily. On a molecular level, a stress fracture is believed to be an example of accelerated bone remodelling (Hajek & Noble 1982); Shoes lose their shock-absorbing abilities with perspiration and may lead to an increased risk of stress fracture over the course of a long run. Additionally, a new pair of running shoes may not be sufficiently 'broken in' to be comfortable for the runner. This may result in an unconscious muscular effort to protect the footfall (Daffner 1982). Symptoms are exacerbated by stress and relieved by inactivity. Patients typically present with bone tenderness and positive findings on a radiograph (Dugan & D'Ambrosia 1983). Treatment consists of rest ranging from 2 weeks to 1 year before running again. Patients should also decrease their distance prior to a change of running surface and should use shock-absorbing shoes (Sullivan et al. 1983). Iliotibial band syndrome causes pain in the lateral aspect of the knee. The literature contains no evidence supporting the theory that this injury may be caused by running shoes. As reported by Nutig (1981), this syndrome is seen after running up hills or climbing stairs. The patient typically reports that walking with the knee in full extension relieves the discomfort. On physical examination, there is tenderness over the lateral epicondyle. The symptoms are most likely due to repeated rubbing back and forth over the epicondyle. It is often seen in tibia vara (genu varum or bowleg). Treatment consists principally of rest and oral anti-inflammatory medication. On occasion, steroid injection may be helpful. Orthotics may also be beneficial in conjunction with a well fit shoe. Anterior compartment syndrome and lateral compartment syndrome are not as frequent as the preceding running injuries, but quite possibly may be related to running shoes. In anterior compartment syndrome, the patient perceives pain in the upper half to two-thirds of the anterolateral upper leg. Pain may also extend to the dorsiflexor tendons of the foot. Problems involved with this syndrome include changing from flatfooted to toe-running, initiating excessive interval or speed training
on a track or hill, and running in shoes that have too much flexibility in the sole. In lateral compartment syndrome, pain occurs around the ankle and lower lateral leg. The sensation of this injury is either pain along the outside of the ankle or the ankle weakness during heavy activity. This occurs in athletes with excessive pronation, or rolling of the foot and arch, when running. Again, if the athlete has proper foot stability while running, such as a good heel counter and heel counter support that prevents overpronation, this injury may partially be alleviated.
6. Conclusion Degenerative changes in bone and cartilage (Radin et al. 1982; Sohn & Micheli 1984) as well as low back pain have been related to impulse loading in the musculoskeletal system (Voloshin & Wosk 1982). The incidence of stress fractures has also been demonstrated to significantly increase as running distance is increased (Sullivan et al. 1984). Along with the physical 'pounding' of the musculoskeletal system and the injuries related to it, it has been suggested that the effect of wet (perspiration or rain) shoes severely lowers the shock absorption of the shoe, thus suggesting greater forces being transmitted to the body (Cook et al. 1985), and greater susceptibility to injuries to the lower extremities. All running shoes lose between 30 and 50% of their shock absorbency characteristics after as little as 400km of running. This number of miles is rapidly reached by serious runners and within 3 or 4 months by less serious runners. The loss of shock absorbency in worn shoes must certainly play a role in overuse injuries. Motion control features in running shoes, particularly the heel counter, play an important role in injury prevention by stabilising the foot during the gait cycle. One must be cautious, however, in the use of shoes with motion control features such as heel wedges intended to prevent overpronation or supination. Many runners do not understand the normal gait cycle and may purchase inappropriate shoes resulting in injury. The decision on the use of such devices is better left to the medical professional.
Running Shoes and Running Injuries
On the positive side, long distance runners, both male and female, have approximately 40% more bone mineral content than matched controls (Panush et al. 1986). This could perhaps be a prophylactic treatment for women who are susceptible to osteoporosis; however, women have more sclerosis and spur formation in their spine and weight-bearing knee x-ray films (Panush et al. 1986). Long and intermediate distance runners who are susceptible to injuries must take all factors into consideration when weighing their overall health status.
References Andrish JT, Bergfeld JA, Walheim J, A prospective study on the management of shin splints. Journal of Bone and Joint Surgery 56A: 1679-1700, 1974 Bates BT, Osternig LR, Sawhill JA, James SL. Design of running shoes. International Conference on Medical Devices and Spons Equipment, ASME Centennial Program Century II, Emerging Technology Conferences, San Francisco, CA, August, 1980 Blair SN. Risk factors and running injuries. Medicine and Science in Spons and Exercise 17(2): xii, 1985 Blair WR. Stress fracture of the proximal fibula. American Journal of Sports Medicine 8(3): 212,1980 Brahms M, Fumick R, Ippolito V. Atypical stress fracture in the tibia of a professional athlete. American Journal of Spons Medicine 8: 131-132, 1980 Brody DM. Running injuries. Clinical Symposia 32(4): 1-36, 1980 Caspersen CJ. Epidemiology of running injuries one year following a 10 km road race. Presented at the 1985 Annual Meeting of the American College of Sports Medicine, Nashville, TN, May 26, 1985 Cavanagh PR, laFortune MA. Ground reaction forces in distance running. Journal of Biomechanics 13(5): 397-406, 1980 Clement DB, Taunton JE, Sman GW, McNicol S. A survey of overuse running injuries. Physician and Sponsmedicine 9: 397406, 1981 Cook SD, Kester MA, Brunet ME. Shock absorption characteristics of running shoes. American Journal of Spons Medicine 13(4): 248-253, 1985 Crossman J. Psychosocial factors and athletic injury. Journal of Spons Medicine and Physical Fitness 25: 151-154, 1985 Daffner RH. Stress fractures in runners. Journal of the American Medical Association 247(7): 1039-1041, 1982 Daffner RH. Stress fractures of proximal tibia in runners. Radiology 142(1): 63-65, 1982 Detmer DE. Chronic leg pain. American Journal of spons Medicine 8(2): 141-144, 1980 Devas M, Sweetnam R. Stress fractures of the fibula. Journal of Bone and Joint Surgery 38B: 818, 1956 Dickinson JA, Cook SD, Leinhardt TM. The measurement of shock waves following heel strike while running. Journal of Biomechanics 18: 415-422, 1985 Drez D. Metatarsal stress fractures. American Journal of Spons Medicine 8(2): 123, 1980 Drez D. Running footwear: examination of the training shoe, the foot, and functional onhotic devices. American Journal of Spons Medicine 8(2): 140-141, 1980 Dugan RC D'Ambrosia R. Fibular stress fractures in runners. Journal of Family Practice 17(3): 415-418, 1983 Editorial. Anicular canilage. Lancet (2): 81-85, 1971
Ellis J. The match game: finding the right shoe for your biomechanics and running gait. Runner's World (October): 66-71, 1985 Galloway JF. Galloway's book on running, Running Advice, Atlanta, 1983 Glick JM, Katch VL. Musculoskeletal injuries in jogging. Archives of Physical Medicine 51: 123-126, 1970 Grana WA, Coniglione TC Knee disorders in runners. Physician and Sponsmedicine 13: 127-133, 1985 Gudas 0. Patterns of lower extremity injury in 224 runners. Comprehensive Therapy 6: 50-59, 1980 Hajek MR, Noble HB. Stress fractures of the femoral neck in joggers: case repons and review of the literature. American Journal of Spons Medicine 10(2): 112-116, 1982 Henderson F. Jog, run, race, p. 155, World Publications, Mountain View, CA, 1977 James OL Brubaker CEo Running mechanics. Journal of the American Medical Association 221: 1014-1016, 1972 James SL, Bates BT, Osternig LR. Injuries to runners. American Journal of Spons Medicine 6: 40-50, 1978 Johnson R. Common running injuries of the leg and foot. Minnesota Medicine: 441-443, 1983a Johnson R. Spons medicine, fitness and nutrition corner: common running injuries of the leg and foot. Minnesota Medicine 441-443, 1983b Kirby KA, Valmassy RL. The runner-patient history: what to ask and why. Journal of the American Podiatry Association 73: 39-43, 1983 Kaplan JP, Powell KE, Sikes RK, Shirley RW, Campbell CC An epidemiological survey of the benefits and risks of running. Journal of the American Medical Association 248: 3118-3121, 1982 Latshaw RF, Kantner TR, Kalenak A, Baum S, Corcoran JJ. A pelvic stress fracture in a female jogger: a case repon. American Journal of Spons Medicine 9( I): 54, 1981 Lutter L. Injuries to the runner and jogger. Minnesota Medicine 63: 45-51, 1980 Miller DI. Biomechanics of running - what should the future hold? Canadian Journal of Spons Science 3: 229-236, 1978 Ellis J. The match game: finding the right shoe for your biomechanics and running gait. Runner's World (October): 66-71, 1985 Misevich KW, Cavanagh PRo Material aspects of modeling shoet foot interaction. Symposium on biomechanical propenies of spon shoes and playing surfaces, Hotel Val Monte, Nifmegen, The Netherlands, Jan 20, 1982 Munro MB, Abernethy PJ, Paul IL, Rose RM, Simon SR, et al. Peak dynamic force in human gait and its attenuation by the soft-tissues. Onhopaedic Research Society 21: 65, 1975 Newell SG, Bramwell ST. Overuse injuries to the knee in runners. Physician and Sponsmedicine 12: 81-92, 1984 Nitz A, Scoville C Use of ultrasound in the early detection of stress fractures of the tibial plateau. Military Medicine 145: 844-846, 1980 Nutig MH. Onhopaedic injuries in runners. Onhopaedic Review 10: 97-100, 1981 Pagliano J, Jackson D. The ultimate study of running injuries. Runner's World (November): 42-50, 1980 Panush RS, Schmidt C Caldwell JR, Edwards NL, Longley S, et al. Is running associated with degenerative joint disease? Journal of the American Medical Association 255(9): 1152-1153, 1986 Paty JG, Swafford D. Adolescent running injuries. Journal of Adolescent Health Care 5(2): 87-90, 1983 Paul IL, Munro MB, Abernethy PJ, Simon SR, Radin EL, et al. Musculo-skeletal shock absorption: relative contribution of bone and soft tissues at various frequencies. Journal of Biomechanics II: 237-239, 1978 Pinshaw R, Atlas V, Noakes TD. The nature and response to
therapy of 196 consecutive injuries seen at a runners' clinic. South African Medical Journal 65: 291-298, 1984 Powell KE, Kohl HW, Caspersen CJ, Blair SN. An epidemiological perspective on the causes of running injuries. Physician and Sportsmedicine 14(6): 100-114, 1986 Pollock ML, Gettman LR, Milesis CA, Bah MD, Surstine L, et al. Effects of frequency and duration of training of attrition and incidence of injury. Medicine and Science in Sports 9: 3136, 1977 Radin EL, Orr RB, Kelman JL, Paul IL, Rose RM. Effect of prolonged walking on concrete on the knees of sheep. Journal of Biomechanics 15: 487-492, 1982 Root ML, O'Brien WP, Week JH. Normal and abnormal function of the foot, Vol. 2, Clinical Biomechanics Corp. Los Angeles, 1977 Root ML. O'Brien WP. Week JH. et al. Biomechanical examination of the foot. Clinical Biomechanics Corp. Los Angeles. 1971 Schlefman BS. Recurrent tibial fractures in a jogger. Journal of the American Podiatry Association 71(10): 577. 1981 Shellock FG. Prentice WE. Warming-up and stretching for improved physical performance and prevention of sports related injuries. Sports Medicine 2: 267-278. 1985 Sohn RS. Micheli U. The effect of running on the pathogenesis
Sports Medicine 10 (1) 1990
of osteoarthritis of the hips and knees. Medicine and Science in Sports and Exercise 16(2): 150, 1984 Stanish WD. Overuse injuries in athletes: a perspective. Medicine and Science in Sports and Exercise 16: 1-7. 1984 Sullivan D. Warren RF. Pavlov H. Kelman G. Stress fractures in 51 runners. Oinical Orthopaedics and Related Research 187: 188-192. 1983 Taunton JE, Oement DB. McNicol K. Plantar fasciitis in runners. Canadian Journal of Applied Sport Sciences 7: 41-44, 1982 Voloshin A. Wosk J. An in vivo study oflow back pain and shock absorption in the human locomotor system. Journal of Biomechanics 15: 21-27, 1982 Voloshin A, Wosk J. Shock absorbing capacity of the human knee (in vitro properties). Proceedings of the Special Conference to the Canadian Society for Biomechanics on 'Human locomotion (', London, Ontario, pp. 104-105, 1980
Correspondence and reprints: Professor Stephen D. Cook. Director. Orthopaedic Research, Department of Orthopaedic Surgery, School of Medicine, Tulane University. 1430 Tulane Avenue, New Orleans. LA 70112, USA.