gait cycle

gait cy·cle

(gāt sīkĕl)

The gait cycle starts when one foot makes contact with the ground and ends when that same foot contacts the ground again. The cycle can be broken down into various phases and periods to determine normative and abnormal gait.

gait cycle

; walking cycle; locomotor cycle sequence of lower-limb events occurring during normal walking (on flat, level surface) and made up of alternating stance phase (itself divided into three periods, during which all or part of foot contacts the support surface) and swing phase (when limb swings forward between the end of one episode of ground contact and start of next); note: first 10% of stance phase is a period of double support, i.e. both feet are in contact with ground surface (Table 1and Table 2; Figure 1)

Table 1: Comparison of gait during walking and running

Walking	Slow running	Fast running
Contact phase (60%) Heel contact Midstance (flat foot) Propulsion (toe off)	Shorter contact phase (50%)	Short contact phase (40%)
5 cm base of gait (intermalleolar distance)	>5 cm base of gait
Short swing phase (40%)	Longer swing phase (70%)	Long swing phase (80%)
Short period of double support (10%)	40% of cycle without support (= airborne phase)	60% of cycle without support (= airborne phase)

Table 2: Foot events occurring during normal bipedal gait

Stance phase	Events/movements occurring
Leg 1
Heel strike (HS)	Leg 1 STJ slightly supinated, so that: • Posterior lateral area of the ‘plantar heel pad’ contacts the ground surface • Forefoot is inverted relative to the ground surface MTJ is also supinated, so that: • Tibialis anterior tendon is contracted and prominent • Limb decelerates Hallux slightly dorsiflexed due to contraction of EHL Leg 2 Knee of supporting leg is flexed Heel off on supporting leg
From heel strike (HS) to foot flat (FF)	Leg 1 STJ begins to pronate due to: • Internal rotations within the lower limb • Friction between the ground surface and the heel MTJ also begins to pronate as: • Tibialis anterior relaxes • Ground reaction forces act on the fifth and fourth metatarsals The plantar heel pad becomes weight-bearing The lateral area, then the whole forefoot, loads rapidly The hallux ceases to dorsiflex as soon as forefoot loading occurs Once forefoot loading in leg 1 is completed (and leg 2 has undergone toe off) the STJ should pronate no further Leg 2 Foot moving through propulsion phase, so that leg 1 loads fully as leg 2 undergoes toe off
From foot flat (FF) to midstance (MS)	Leg 1 The leg and pelvis undergo external rotation • STJ supinates The knee is extended • A bisecting line through the knee exits through the middle of the second metatarsal • Leg 2 begins its swing phase Midstance occurs when the leg is perpendicular to the ground • The leg is directly over the foot • STJ is neutral • Tibialis anterior is relaxed • Weight is evenly distributed across the heel pad • MTJ is fully pronated • Toes are flat to the ground surface, with no plantarflexion of the digits • Leg 2 is in the middle of the swing phase and passes leg 1
Midstance (MS) to toe off (TO)	Leg 1 As the body weight moves anteriorly over the foot, simultaneously: • The knee flexes rapidly • Gastrocnemius fires to bring about heel lift (just prior to heel contact of leg 2) • Body weight transfers to the forefoot The foot is supinating (due to the pull of gastrocnemius) • There is no movement of the STJ, only movement at the MTJ • MTJ locks to convert the foot to a rigid lever Propulsion begins • Body weight is distributed across the metatarsal heads • First MTPJ is dorsiflexed but both first and fifth rays are parallel to the support surface Propulsion continues • The body weight continues to moves further forward • First metatarsal plantarflexes and plantar aspect of first MTPJ becomes prominent • Remainder of the foot supinates relative to the first ray and the height of the MLA increases • Peroneus longus fires to stabilize the first ray (peroneus longus tendon becomes prominent) • Body weight transfers from the lateral to the medial side of the foot • Lateral aspect of the forefoot lifts (assists transference of body weight to leg 2) • STJ supination reduces as foot begins to unload
Swing phase	Events/movements occurring
Leg 1
Early swing	Plantar aspect of first MTPJ still prominent Toes dorsiflexed at MTPJs to allow ground clearance during swing
Midswing	Plantar aspect of first MTPJ no longer prominent
Late swing	STJ and MTJ supinated due to contraction of tibialis anterior, EHL and EDL muscles
STJ, subtalar joint; MTJ, metatarsal joint; EHL, extensor hallucis longus; MTPJ, metatarsophalangeal joint; MLA, medial longitudinal arch; EDL, extensor digitorum longus.

Figure 1: Gait cycle: B: heel contact; C: early foot flat; D: late foot flat; E: toe oll; F: trajectory of centre of pressure during stance phase the gait. This article was published in Neale's Disorders of the Foot, Lorimer, French, O'Donnell, Burrow, Wall, Copyright Elsevier, (2006).