Biomechanics and Analysis of Running Gait

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608 DUGAN & BHATThe anatomic uniqueness of the plantar fascia also helps to create thesolid structural platform that is needed for propulsion. It originates fromthe medial tubercle of the calcaneus and inserts around the metatarsal headsto the base of the proximal phalanges. It crosses the transverse tarsaland metatarsophalangeal joints and serves as a passive restraint. At themetatarsophalangeal attachment, the Spanish windlass mechanism isformed (Fig. 3). As extension occurs at the metatarsophalangeal joint justbefore toe-off, the plantar fascia tightens and pulls the calcaneus andmetatarsal heads together [9]. This heightens the longitudinal arch of thefoot and forces the transverse tarsal joint into a forced flexion position, andthereby, creates a solid structural support. In addition, the intrinsic footmuscles actively contract to provide further stability of the foot.The ligaments within the foot also provide passive stability. Ligaments,along with muscular support and the unique bone architecture of the foot,form two longitudinal arches (medial and lateral) and a transverse arch. Themedial foot ligaments are thicker than the lateral ligaments. This designprevents hyperpronation during ambulation. The arches of the foot createweight-bearing points, primarily on the calcaneus and the metatarsal heads.The sesamoid bones decrease force on the plantar surface of the firstmetatarsal head just before toe-off. The unique configuration of these archesallows the foot to be mobile to adjust to the ground surface and rigid inpreparation to push off the ground for the sake of propulsion.Fig. 3. The windlass mechanism. After heel-off, metatarsophalangeal extension increasestension on the plantar fascia (converging arrows). The transverse tarsal joint is forced intoflexion (arrowhead), which increases stability as the foot prepares to push off. (From GeiringerSR. Biomechanics of the running foot and related injuries. Phys Med Rehabil State Art Rev1997;11(3):569–82; with permission.)
BIOMECHANICS & ANALYSIS OF RUNNING GAIT609The muscles of the lower leg and foot work in an eccentric and concentricfashion. Eccentric work is muscle contraction while fibers are lengthening;concentric work is muscle contraction while fibers are shortening. Withrunning, the greatest amount of muscle work is done in an eccentric fashion.The pronation phase of gait involves mostly eccentric contraction to providefor joint control and shock absorption. The supination phase of gaitinvolves mostly concentric contraction of various muscles, particularly thegluteals, to provide for acceleration and propulsion.Although muscles can work in all three planes, muscle fiber orientationoften dictates a preferred plane. For instance, the gluteus maximus hasmuscle fibers that are oriented in an oblique (transverse) fashion; therefore,this powerful muscle becomes an ideal leg external rotator (by way ofconcentric contraction) and controls leg internal rotation (by way ofeccentric contraction). Another key muscle in running is the gastrosoleuscomplex, commonly considered to be a pure plantarflexor. Yet, this complexalso contributes to the transverse plane motion of hindfoot inversionbecause of its location in relation to the STJ axis [8]. This allows thegastrocnemius-soleus to contribute to supination as the foot progressesthrough the gait cycle.Walking versus runningRunning, like walking, is a series of pronations and supinations. Runningis distinguished from walking by increased velocity, or distance traveled perunit time, and the presence of an airborne or float phase (Box 2). Judges inrace walking determine that participants are running illegally if they observea period of time when both feet are off the ground. During a running gaitcycle, there are two periods of float when neither foot is in contact with theground (Fig. 4). This results in decreased time in stance phase and increasedBox 2. Differences between running and walkingIncreased velocityIncreased ground reaction forcesFloat phaseNo double stance phaseDecreased stance phase and increased swing phaseOverlap of swing phase rather than stance phaseRequires more range of motion of all lower limb jointsRequires greater eccentric muscle contractionInitial contact varies, depending on speedDecreased center of gravity with increased speedDecreased base of support
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Biomechanics and Analysis of Running Gait

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