Biomechanical Differences: Male and Female Marathon Runner

Biomechanical Differences: Male and Female Marathon Runner More than by brain size or tool-making ability, the human species was set apart from its ancestors by the ability to jog mile after lung-stabbing mile with greater endurance than any other primate. The introductory quotation (Hotz, 2004) simply, yet vividly, expresses the results of a recent study completed by two American scientists, Dennis Bramble and Daniel Lieberman, and released in the journal Nature(2004). Bramble and Lieberman contend that the ability to run long distances was the driving force shaping the modern human anatomy.Hotz’s characterization of early humans as marathon men and women from the tips of their distinctively short toes and long Achilles tendons to the tops of their biomechanically balanced heads (emphasis added) sets the backdrop for this essay—an exploration of the biomechanical differences between male and female marathon runners. After a few additional historical comments, this essay opens with a presentation of anatomical differences between men and women with specific reference to running then continues with definitions and descriptions of the term marathon, as a form of organized running sport, and definitions for the term biomechanics in preparation for a discussion of how the field of biomechanics is applied to running. With this information as a foundation, the objective and scope will be articulated followed by presentation of previous methods and findings revealed from a search of the literature on the topic of biomechanical differences between male and female marathon runners and closely-related topics. These findings will be discussed and conclusions drawn. Finally, recommendations for further research will be presented. To return briefly to the research findings of Bramble, a paleontologist and biomechanics expert, and Lieberman, a physical anthropologist, to continue setting the backdrop for the essay, Bramble states: Running made us human, at least in an anatomical sense. We think running is one of the most transforming events in human history (Chui, 2004). Endurance running is an activity that is reserved for humans in the primate world and not common in other mammals with the exception of dogs, horses and a few others. Bramble and Lieberman contend that running permitted humans to scavenge and hunt for food over significant distances and that the high protein food they secured was instrumental in developing larger brains (Wilford, 2004). To facilitate running, humans developed several traits including large buttocks with strong muscles which connect the femur to the trunk of the body preventing the body from over-balancing with each step. In addition, humans have a lengthy arm-swinging stride and [l]ong ligaments and tendons—including the Achilles tendon—[which] serve as springs that store and release mechanical energy during running.(Hotz, 2004). Bramble’s reference to today’s running in the evolutionary context he and Lieberman established provides an appropriate introduction to the exploration of the biomechanical differences between male and female marathon runners (Wilford, 2004): Today, endurance running is primarily a form of exercise and recreation, but its roots may be as ancient as the origin of the human genus. The description of anatomical differences between men and women,which is focused on anatomical features that are involved in running,begins with a gender-neutral discussion to establish a foundation for the more gender-specific information. Rossi (2003) emphasizes the complexity of walking, a precursor torunning. He writes that half of the 650 muscles and tendons in thehuman body are involved in what most people consider to be the simpleact of walking. He suggests that, in the evolution of the human body,there were hundreds of adaptations that had to take place,adaptations that required repositioning of everything in the bodyover several million years. Rossi writes: The arms, no longer needed for branch swinging, became shorter, thelegs longer, the pelvis wider, the shoulders narrower, the neck longerand more slender, the spine changed from C-shape to S-shape. Majorchanges were required in the hip, knee and ankle joints. Hundreds ofmuscles, tendons, ligaments and joints gradually shifted in position,size and function. And of course, the new posture and gait requiredimportant changes in the size and position of all the organs of thechest and abdomen. Rossi suggests that some of these changes were extremely significantfrom a biomechanical perspective. For instance, he calls attention tothe blood pumping requirement of the upright human form: Daily in eachindividual, approximately 74,000 quarts of blood must travel through100,000 miles of blood vessels from the brain to the feet and legs in acircular pattern. Rossi emphasizes the human engineering challengethat was required to design a system that would counteract the effectsof gravity in moving blood vertically in this manner. Rossi’s commentsare particularly important in the context of the current discoursebecause they provide some insight into the current state of relevantanatomical features of today’s runners and how those features werederived. The anatomy of humans, unlike that of other living creatures,provides for speed and endurance. The unique characteristics related torunning include (Science in Africa, 2005, citing University of Utah Public Relations, 2004): †¢ Skull features. These features, which include sweating from the scalp and face, cool the blood. †¢ A balanced head. This shape of head with a relatively flat face,small teeth, and short snout moves the center of the mass backwardwhich helps to counter the effects of moving upward and downward duringrunning. †¢ A ligament running from the rear of the skill and neck downward tothe thoracic vertebrae. This feature serves as a shock absorber thataids the arms and shoulders in counterbalancing the head during runningactivity. †¢ Shoulders decoupled from the head and neck. This feature allowsrotation of the body while the head faces forward during running. †¢ A tall body. This feature, which includes a narrow trunk, waistand pelvis, provides for increased skin surface allowing for enhancedbody cooling and permits the upper and lower body segments to moveindependently. †¢ Short forearms. This feature permits the upper body to act as acounterbalance to the lower body during running activity while reducingthe muscle power required for maintaining flexed arms. †¢ Large vertebrae and disks. This feature permits the human back to accepted heavier loads when runners impact the ground. †¢ Large, strong connection between the pelvis and the spine. Thisfeature supports more stability and shock absorbing capacity duringrunning activity. †¢ Large buttocks. This feature, and the muscles that form it,stabilize the body during running activity. The connection of thesemuscles to the femur prevents the body from pitching forward. †¢ Long legs. This feature allows humans to take large strides duringrunning activity. The tendons and ligaments permit the legs to belighter and less muscular thereby requiring a smaller amount of energyto propel them while running. †¢ Large hip, knee, and ankle joint surface areas. These featuresprovide enhanced shock absorption by reducing the impact in any onespecific area. †¢ Arrangement of bones in the foot. This feature provides for a morerigid foot by creating a stable arch, allowing runners to push off in amore efficient manner and to use ligaments located on the bottom of thefeet as springs. †¢ Large heel bone, short toes, and a big toe. These features providefor enhanced shock absorption and increased capacity to push off duringrunning activity. With the running-related anatomical features applicable to allhumans as a foundation, the focus now turns to the differences inanatomical features between men and women, specifically those featuresthat are involved in running activity. Holschen (2004) writes that,until puberty, males and females are equal in terms of strength,aerobic power, heart size, and weight; they also have similar amountsof body fat. Starting at puberty, according to Holschen (2004), male and female sexhormones begin affecting bone and lean body mass, circulation, andmetabolism in different ways. A female typically has a wider pelvis,femoral anteversion (inward twisting of the femur), genu valgum (kneestouch but ankles are separated), and external tibial torsion (feet donot line up in a straight manner because of out-toeing from outwardrotation of the large calf bone). Center of gravity differences betweenmen and women are minimal, correlating more by body type and heightthan with gender. (Atwater, 1985, cited in Holschen, 2004). Whencompared with males, females typically have smaller bones accompaniedby smaller articular surfaces. They also have proportionately shorterlegs with resulting decreased potential force in certain maneuvers.(Holschen, 2004). At puberty, girls gain both fat and lean muscle mass due to theinfluence of female hormones; boys lose body fat and add muscle massdue to the influence of male hormones (Holschen, 2004). Women inadulthood have about ten percent more body fat than do their malecounterparts (Greydanus, D. and Patel, D., 2002, cited in Holschen,2004). The basal metabolic rate is approximately ten percent lower inwomen than in men. The presence of female hormones mandates that womenrely more on fat metabolism at any given exercise level when comparedto men. In addition, glycogen uptake, storage, and use are increased.(Holschen, 2004, citing Bonekat, H. W. et al., 1987; Dombovy, M. L. etal., 1987; Frankovich, R. J. and Lebrun, C. M., 2000; Nicklas, B. J. etal., 1989; Tarnopolsky, L. J., 1990) Cureton and associates (1988,cited in Holschen, 2004) attribute the differences in muscle strengthbetween men and woman to skeletal and cardiac muscular hypertrophy andmuscle mass percentage; they contend that muscle mass in men is fortypercent compared to twenty-three percent in women. Changes in body composition and circulatory capacity beginning atpuberty result in approximately twenty percent highercardio-respiratory capacity in men. Men also have comparatively higheroxygen-carrying capacity, larger heart and lung mass, a higher strokevolume, and higher maximal cardiac output which result in greatereffectiveness in aerobic and anaerobic activities, although trainingcan overcome the inherent differences (Williford, H. N. et al., 1993,cited in Holschen, 2004). The results of the current research point to fundamental anatomicaldifferences between men and woman, differences that largely begin toappear during puberty and which have some bearing on runningcapability. The term running can be defined as [moving] swiftly on foot sothat both feet leave the ground during each stride (American HeritageDictionary of the English Language, 2000). The research by Bramble andLieberman (2004, cited in Nature, 2004), which was presented earlier,seems to indicate that running has been part of human existence sinceits beginnings and, in fact, contributed significantly to developmentof human life today. Humans no longer require running for survival, atleast in their normal affairs; that is, typically, humans do not haveto run from danger or run in pursuit of animals to kill for food. Inmodern times, running has taken on a new form—competition foot racing.This competition racing can be against oneself to achieve one’s ownpersonal best or with others. Racing against others can take manyforms ranging from informal competitions between two young friendsracing against one another on a playground to very formal competitionssuch as those in the quadrennia l Olympics. The more formal runningcompetitions are typically classified by the length of the run: 100,200, 400, 800, 1500, 5000, and 10000 meters as well as marathons(Dollman, 2003). There are many terms that refer to specific forms of foot racing: run,dash, sprint, relay, meet, competitive trial of speed, footrace, andmarathon (Webster’s New World Thesaurus, 1997). Of these, the termsdash and sprint are typically used interchangeably to describe ashort, fast run or race (Webster’s New World Dictionary, 1988) or ashort, swift movement (Webster’s New World Thesaurus, 1997). Organizeddashes and sprints are commonly of 50 meters, 100 meters, 200 meters,50 yards, 100 yards, and 200 yards in length (Webster’s New WorldThesaurus, 1997). Marathons are a form of long-distance running, whichare on- and off-the-track competitions of more than 3000 meters (Hlus,1997). Specifically, a marathon is a footrace of 42 kilometers, 195meters (26 miles, 385 yards) run over an open course, or anylong-distance or endurance contest People who compete in marathons arecalled marathoners (Webster’s New World Dictionary, 1998).Physiologically, there is a fundamental difference between a sprint ordash and a marathon. According to Pritchard (1994), A sprinter canexert maximum force throughout the run, but this is not possible forlonger runs, where propulsive force must be reduced to match energyavailability. Historically, marathons are not new events. According to legend, thename marathon is derived from the Greek city, Marathon, to commemoratePheidippides’s run from that city to Athens to announce Greek victoryover the Persians. The marathon was introduced to the Olympics in 1896and today’s official distance was established in 1908. (Hlus, 1997; TheColumbia Encyclopedia, 2005) Today, in addition to marathon races inthe Olympics, many cities throughout the world serve as sites forannual or other periodic marathons (The Columbia Encyclopedia, 2005). A new form of marathon race has recently taken form—the ultramarathon,which is any organized footrace extending beyond the standard marathonrunning distance of 42 kilometers, 195 meters†¦[they] typically begin at 50 kilometers and extend to enormous distances (Blaikie, n. d.).Standard distances for ultramarathons are 50 and 100 kilometers and 50and 100 miles (Meyers, 2002) with the longest certified race being theSri Chinmoy, a 2092 kilometer race held annually in New York (Blaikie,n. d.). The research produced numerous and varied definitions for the termbiomechanics. The following are representative of the findings: †¢ The study of the mechanics of a living body, especially of theforces exerted by muscles and gravity on the skeletal structure. (TheAmerican Heritage Dictionary of the English Language, 2000). †¢ [The] application of mechanical engineering principles andtechniques in the field of medicine and surgery, studying naturalstructures to improve those produced by humans (The HutchinsonEncyclopedia, 2003). †¢ [A] science examining the forces acting upon and within a biologicalstructure, and the effects produced by those forces (The University ofCalgary, n. d.). †¢ [T]he science that deals with forces and their effects, applied to biological systems (Freivalds, 2004). †¢ [T]he application of the principles and techniques of mechanics to the human body in motion (Snowden, 2001). †¢ Biomechanics is a specific field which evaluates the motion of aliving organism†¦and the actions of forces on that organism†¦acombination of several different areas of study [including] anatomy andphysiology, kinematics (the study of motion without regard to itscauses), kinesiology (the study of human movement) and kinetics (thestudy of forces acting on a system) (National Endurance SportsTrainers Association, 2005). In furnishing a definition for biomechanics, the Quintic ConsultancyLtd. (2005) provides some additional insight into the origin anddetails of the term, stating that the name is derived from the Greekbios meaning life and mekhaniki meaning mechanics, adding that theseindividual terms are combined to mean the mechanics of life forms.The biomechanics discipline includes research into various life formsincluding plants, insects, reptiles, birds, fish, humans, and others.Within the human specialty, topics include mechanics of bone, tooth,muscle, tendon, ligament, cartilage, skin, prostheses, blood flow, airflow, eye movement, joint movement [and] whole body movement (TheQuintic Consultancy Ltd., 2005). Historically, according to Knudson (2003), the study of humanbiomechanics has alternated between emphasizing each of its twocomponents—the biological and the mechanical. Atwater (1980, cited inKnudson, 2003) claims that, during the first half of the twentiethcentury, scholars emphasized medicine and anatomy under the termkinesiology. The distinct field of biomechanics was born from the workof biomechanists in the 1960s and 1970s. From that point the fieldbegan to emphasize mechanics over biology. Today, the competing forcesto move the discipline either toward a biological emphasis or toward amechanical emphasis continue (Knudson, 2003). The field of biomechanics, already narrowed in a previous sectionfrom consideration of all life forms to only humans for the purpose ofthis essay, can be focused even further to a sub-field called sportsbiomechanics (The Quintic Consultancy Ltd., 2005): Sports biomechanics uses the scientific methods of mechanics tostudy the effects of various forces on the sports performer. It isconcerned, in particular, with the forces that act on the humanneuromusculoskeletal system, velocities, accelerations, torque,momentum, and inertia. It also considers aspects of the behavior ofsports implements, footwear and surfaces where these affect athleticperformance or injury prevention. Sports biomechanics can be divided upinto two sections: performance improvement [and] injury prevention. The Australian Sports Commission (n. d.) furnishes additionaldescriptive information on the application of biomechanics to sports,using a term the Commission calls applied sports biomechanics whichincorporates techniques from physics, human anatomy, mathematics,computing and engineering to analyse technique to prevent injury andimprove performance. The Commission’s division of sports biomechanicsinto two categories—performance improvement and injuryprevention—echoes the classifications offered by The QuinticConsultancy Ltd. Williams (2003) describes how biomechanics can help runnerperformance, specifically that of the marathoner. Leading into hisrecommendations, he describes how marathon runners use a simplebiomechanical strategy known as drafting off another runner whenrunning into the wind to reduce the adverse effects of air resistanceand reduce oxygen consumption for the latter part of the race. Hewrites: The goal of the sport biomechanist is to improve movement efficiency,mainly by maximizing propulsive forces and minimizing resistive forces,and thus provide the athlete with a mechanical edge. Using high-speedcinematography, the biomechanist can analyze a runner’s form and detectproblems in running form that may be inefficient, such as overstriding,and that may waste energy. Although most elite and experiencedmarathoners have developed efficient running styles, even a smallimprovement in running efficiency may make a significant differenceover the duration of a marathon. In addition to the strategy of drafting off another runner,Williams offers several other biomechanical strategies includingselecting the proper sportswear (i.e. uniform and shoes) and optimizingbody weight and composition. Thus far the topics of anatomical differences between men and womenwith specific reference to running; definitions and descriptions of theterms marathon (as an organized, competitive form of running) andbiomechanics; and the application of biomechanics to running have beenpresented and discussed. With this as a foundation, the focus of thediscourse now turns to the topic of biomechanical differences betweenmale and female marathon runners and closely-related topics. The objective of this portion of the essay will be to explore thebiomechanical differences between male and female marathon runnersthrough a review and analysis of selected literature on the topic andrelated issues. The scope of the literature review will include marathon running withspecific reference to available information on the differences betweenmales and females. Although running of shorter distances (e.g. sprintsand dashes) and longer distances (e.g. ultramarathons) as well as othersports activities are excluded from the specific scope of this essay,references will be made to these activities when they related tomarathon running. Performance improvement and injury prevention werementioned as the two primary areas addressed by applied sportsbiomechanics. Gender-specific issues in each of these areas will beexplored briefly as well. REVIEW OF EXISTING RESEARCH ON METHODS AND FINDINGS One researcher who has studied gender differences in enduranceperformance, including marathon running, is Stephen Seiler (1996) ofThe Institute for Sport, Agder College in Kristianstad, Norway. Hewrites: Some years ago it was proposed by some that women wouldactually perform better [than men] at ultra-endurance type activities.This theory has been disproved in the laboratory and in practice. Aslong as women are women, I don’t think they will surpass men, statesNorways perennial marathon winner Grete Waitz (quoted in Holden,2004). The anatomical differences between females and their malecounterparts, specifically those that affect running, were presented inthe introduction. Now an attempt will be made to show that the generalanatomical differences between men and women extend to biomechanicaldifferences that affect marathon running performance and injury. Holschen (2004) writes that [T]he female athlete remains less wellunderstood and less well studied compared with male athletes,especially in the areas of performance factors, repetitive stress, andacute injuries. She continues: Logical reasons for this include: (a)a limited two-generation span of the high-profile elite female; (b)fewer females involved in coaching, research, and sports medicine; and(c) limited areas of female youth sports historically (gymnastics,swimming, dance). The reality of Holschen’s findings proved to be truein the current research activity. There were remarkably few availablesources on the biomechanics involved in women’s marathon running. Mostof the research either applied to males or did not identify the gender.Results from a review of selected research literature will be presentedin this section beginning with gender-differentiated research resultson running performance. Following this, results of research into thetwo applied sports biomechan ics specialties will be presented with afocus on studies concerning footwear and injuries. Holden (2004) writes about performance in running with specialattention to female runners. She quotes physiologist Henrik Larsen ofthe Copenhagen Muscle Research Centre in explaining women’s marathonperformance vis-à  -vis men: Women had not developed long distance;that’s why the improvement is much greater on the marathon. Larsen,who seems to attribute the performance improvements of femalemarathoners to focused training instead of anatomic factors, claimsthat [w]e don’t see any higher oxidative capacity in women. Holdenalso offers comments by exercise physiologist Timothy Noakes of theUniversity of Cape Town, South Africa who agrees with Larsen’sassessment: A smaller body frame gives women an edge on endurance†¦butmen can run 10% faster even when the difference in body size iscontrolled for. Stephen Seiler (1996), who was quoted at the start of this sectionstating that the proposal that women could perform better inultra-endurance activities has been disproved, confirms that there aresome physiological differences between the sexes that impactperformance in females independent of age. He notes that there is aten percent difference in marathon times between men and women, addingthat this difference is the same across the distance runningperformance spectrum. He attributes this difference, not to adifference in training, but to physiological differences. He studiedmaximal oxygen consumption, the lactate threshold, and efficiency toanalyze the differences between men and women as these factors mightaffect long-distance running performance: †¢ Maximal Oxygen Consumption. There is a 43 percent differencebetween men and women with men possessing a VO2 max (oxygen-deliveringcapacity measure) of 3.5 liters per minute and women with a capacity of2.0 liters per minute. Seiler attributes this in part to male size; menare larger. But, even when size is factored in, male oxygen consumptioncapacity is still fifteen to twenty percent higher. Males have agreater capacity to deliver oxygen to their muscles and organs. †¢ The Lactate Threshold. This is the point at which lactic acidbegins to accumulate at higher than normal levels in the blood streamindicating an exercise intensity boundary at which the level ofintensity can be maintained over a long period and that which willresult in quick fatigue. Seiler does not believe that lactatethresholds are different for men and women as a percentage of their VO2max. †¢ Efficiency. After finding conflicting information comparing theefficiency of males and females—revealing that females are lessefficient, more efficient, or the same as males in terms ofefficiency—Seiler believes that differences in efficiency do notaccount for the differences in endurance performance. Seiler concludes with his determination that the ten percentperformance difference between men and women in endurance running canbe attributed to the first of the three physiological factors hestudied—maximal oxygen consumption. Another researcher who explored gender differences in athletics,and especially in endurance events, is Dollman (2003). Citing Shepard(2000), Dollman writes that there is consistent evidence, based onobservations, that males possess larger measures of the following(quoted): †¢ Heart volume, even when corrected for stature. †¢ Haematocrit, which gives males a 13 percent greater oxygen-carrying capacity than females. †¢ Plasma volume. †¢ Total muscle mass, which means that females perform the sameabsolute task at a higher percentage of maximum voluntary contraction,with concomitant vascular impedance limiting cardiac ejection and peakcardiac output. In addition, male skeletal muscles may have a higher succinatedehydrogenase (an integral membrane protein) concentration (Dollman,2003, citing Costill, et al., 1987). Males may produce bettermechanical efficiency during running (Dollman, 2003, citing Miura,1997) although this is arguable as it may be rooted in cultural origins(Dollman, 2003, citing Shepard, 2000). Now attention will turn briefly to a review of selected researchinto the two primary application areas addressed by applied sportsbiomechanics: running performance and injuries. Regarding performance,footwear will be discussed followed by a presentation of selectedfindings on research into injuries. Gender issues will be introduced. Lipsky (2001, citing Hennig, 2001) presented research findings ongender-specific requirements for athletic footwear designed forrunning. The research experiment involved fifteen women and seventeenmen of the same body weights, heights, and ages. Each subject wore thesame shoe size and each tested five types of shoes which included threestyles of men’s shoes and two styles for women. Using Kistler forceplatforms at a set velocity, ground force reactions, tibialacceleration, angular foot motion, and plantar pressures at eightstrategic locations on the foot were measured. According to Lipsky, theexperiment revealed that none of the variables demonstrated asignificant interaction among gender and footwear type meaning, Lipskycontends, that women had the same biomechanical dilemmas in men’sshoes as they did in their own footwear. Despite similarity in thetest subjects’ weight and other factors, men exhibited higher pressurerates in all regions of the foot. Men had sig nificantly higher heelloads, but less midfoot loads, indicating that the arches of women donot support the middle of their feet. According to Lipsky, theseresults support the conclusions that women have a stronger collapse ofthe longitudinal arch†¦during weight bearing and have an increasedtendency of pronation and the smaller amount of pressure to theground. The recommendation from this study is that women should selectrunning shoes that protect against overpronation. This, according toLipsky, will help prevent knee injuries. Bartold (2004) adds to the literature on the differences inrequirements for athletic shoes for men and women. He claims thatrunning footwear is largely designed and manufactured for malerunners, making little recognition that women have significant injuryissues compared to men. Although Bartold acknowledges that reasons forinjuries are not scientifically established, he indicates thatproposals have been made that known differences in structure maypredispose female athletes to differences in running mechanics, andthese differences may lead to specific injuries, continuing by statingthat [a]necdotally, we have excellent evidence [that] the particularbiomechanics of female athletes and the way they run predisposes themto specific injury patterns. With regard to injuries, Parfit (1994) compared running injuries ofmiddle distance runners and marathon runners, concluding that thelatter incur more injuries when compared to the former (approximatelyeighty-two percent for middle distance runners compared to ninety-sevenpercent for marathoners). Acknowledging validity questions due to smallrunner populations studied and lack of injury definitions, Parfit foundthat whilst marathon runners suffered from back problems and hipailments, middle distance runners were more susceptible to kneeproblems, stress fractures, and shin splints. Certain types of knee, shoulder and back injuries are more commonin females and can in part be attributed to differences in body shapeand biomechanics, reports Glasgow, Scotland’s Daily Record (2004).Taunton et al. (2002) found that there were significant differencesbetween running injuries incurred by men and women. According to thisstudy, knee injuries seemed to be the most common injury in both sexeswith men experiencing higher incidences of the following injuries (thefirst percentage shown in parenthesis is for men; the second forwomen): †¢ plantar fasciitis, an injury to the fascia connective tissue on the bottom of the foot (54%/46%); †¢ meniscal injury, a condition in the knee cartilage that acts ascushion between the thigh bone (femur) and shin bone (tibia) (69%/31%); †¢ patellar tendinopathy, a rupture in the tendon that connects the kneecap to the tibia (57%/43%); †¢ Achilles tendinopathy, tendon pain or dysfunction in the muscle that connects the calf to the heel of the foot (58%/42%); †¢ gastrocnemius injury, a condition in the largest, most prominentmuscle in the calf which allows for extending the foot and bending theknee (70%/30%); †¢ adductor injury, a condition, such as a tear, in the muscle in the inner thigh (68%/32%); and †¢ osteoarthritis of the knee, a degenerative joint diseasecharacterized by breakdown of the articular cartilage in the joint(71%/29%). The study by Taunton et al. (2002) revealed that women experiencedhigher incidences of the following running injuries (the firstpercentage shown in parenthesis is for women; the second for men): †¢ PFPS, or patellofemoral pain syndrome, a pain behind the kneesometimes known as runner’s knee (62%/32%, does not add to 100%); †¢ ITBFS, or iliotibial band friction syndrome, a conditioncharacterized by injury to the thick band of fibrous tissue that runsdown the outside of the leg beginning at the hip and extending to theouter side of the shin bone just below the knee joint (62%/32%, doesnot ad