Gait Cycle

Gait • Normal human gait repeats a basic sequence of limb motions that serve to progress the body along a desired path while maintaining weight-bearing stability, conserving energy, and absorbing the shock of floor impact.

Rancho Los Amigos National Rehab Center

Gait • Movements that produces locomotion • Characteristics: – Energy-economical, particularly walking – Flexibility to cope with different speeds, terrains etc. – Sophisticated control mechanisms (bipedal gait inherently unstable)

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Gait • Gait - manner or style of walking • Walking is a learned complex behavior involving the alternate balancing of the body’s weight over a single support while controlling forward motion • At least one foot is always in contact with the ground and the forward fall of the body weight is the major propelling force

Gait Cycle • Normal Gait – Series of rhythmical , alternating movements of the trunk & limbs which result in the forward progression of the center of gravity – Series of ‘controlled falls’

Gait Cycle • The time from the point at which the heel of one foot touches the ground to the time it touches the ground again

Gait Cycle • Objectives – Resist/Dissipate Forces – Maintain Balance – Move Body in Intended Direction – Conserve Energy

Resist/Dissipate Forces • Source of Forces – Gravity – Muscle Contraction – Inertia

Maintain Balance • Support • Keep upright • Avoid collapse • Obstacle avoidance and foot placement • Foot clearance • Negotiate your way through the world

Maintain Balance • Dynamic Movement • Influenced by external factors • Single versus Double Support • Depends on Multiple Systems • Adaptations in Base of Support

Move Body in Intended Direction • Safely move the center of mass (CM) forward • Turn when necessary • Maintain an oscillatory pattern • Re-Positioning of Center of Gravity • Re-Positioning of Limb Segments

Energy conservation • Smoothness • Minimize pain • Adapt gait to avoid painful forces or motions

Gait Cycle - Definitions:

Gait Cycle - Definitions: • Step Length – Distance between corresponding successive points of heel contact of the opposite feet

• Stride Length – Distance between successive points of heel contact of the same foot – Double the step length

Gait Cycle - Definitions: • Walking Base – Side-to-side distance between the line of the two feet – Also known as ‘stride width’

• Cadence – Number of steps per unit time – Cultural/social variations

Gait Cycle • During one gait cycle, each extremity passes through two phases • Stance phase - a given foot is in contact with the ground, heel-strike to toe-off, 60% • Swing phase - a given foot is in the air, toeoff to heel stride, 40%

Gait Cycle

Gait Cycle Initial Contact

Initial Contac t

Stride Stance (60%) Double Support

0%

10

Single Support

Swing(40 %) Double Support

50

60

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Gait Cycle • Stance phase – Contact Period • Heel strike to forefoot loading

– Midstance Period • Forefoot loading to heel raise

– Propulsive Period • Heel raise to toe off

Contact Period • Heel strike to forefoot loading • Foot pronates at subtalar joint • Only time (stance phase) normal pronation occurs • This absorbs shock & adapts foot to uneven surfaces • Ground reaction forces peak • Leg is internally rotating • Ends with metatarsal heads contacting ground

Midstance Period • Forefoot loading to heel raise • Foot stops pronating & starts supinating due to Tibialis posterior & Soleus contract • And external rotation of the leg • Other leg in swing phase – all weight on one foot • Vertical ground reaction forces decrease – body is directly over foot • Ends as heel leaves ground

Propulsive Period • Heel raise to toe off • Subtalar joint supination continues until just after toe off • Leg continues to externally rotate • Vertical ground reaction forces peak – forefoot only bearing weight on this side • Forces move from lateral to medial passing through the hallux • First MPJ must function correctly for maximum efficiency • Toes are loaded to stabilise MPJ’s

Gait Cycle

• Swing phase – Acceleration – Midswing – Deceleration

Swing Phase • Foot accelerates to “catch up” with body • Leg internally rotates (from external position) • Foot pronates to aid ground clearance • Foot decelerates and slightly supinates in preparation for heel strike

• Time Frame: A. Stance vs. Swing: • Stance phase = 60% of gait cycle • Swing phase = 40% B. Single vs. Double support: • Single support= 40% of gait cycle • Double support= 20%

Gait Cycle - Components:

• Support: (1) Single Support: only one foot in contact with the floor (2) Double Support: both feet in contact with floor

Cycle Divisions • Stance Phase • Begins with heel strike and ends when the toe leaves the ground • Weight is transferred from the heel to the head of the metatarsals as the center of gravity passes forward over the foot • divided into 5 phases

Cycle Divisions • Initial contact – Beginning of Loading – Foot Position may vary, but is generally supinated – Represents end of single support on the opposite side

Cycle Divisions • Initial contact – Contact should be through lateral aspect of plantar surface – Opposite limb is ending with toe-off – Subtalar joint – supinated @ 5 degrees – Talocrural joint – dorsiflexed – Both limbs in contact with surface

Cycle Divisions • Loading response – The limb reacts to the weight of the body by rolling forward on the heel to sustain body momentum – The foot is brought into full contact with the ground – Maximum Impact Loading occurs

Cycle Divisions • Loading response – Response to absorption of body weight by initiating flattening of the foot – Subtalar joint – pronates • Unlocks midtarsal joints, allowing foot to become flexible • Tibial internal rotation – increased medial forces at foot, leg, knee

– Talocrural joint – plantarflexes – Foot rapidly moves into pronation

Cycle Divisions • Midstance – Begins the interval of single stance – An ankle rocking action occurs to bring the body weight over the planted foot this helps sustain the body’s forward momentum – All weight supported by single leg

Cycle Divisions • Midstance – Subtalar joint – supinates • Locks midtarsal joints, makes foot a rigid lever • Preparing for efficiency during propulsion

– Talocrural joint – dorsiflexes

Cycle Divisions • Terminal stance – Begins with raising the heel (heel-off) – The lower limb rolls forward on to its forefoot and the body advances ahead of the solesupporting foot

Terminal Stance • Terminal stance – Provides new base of support – Toes extended, tibia externally rotated – Subtalar joint – supinated – Foot remains pronated initially then resupinates

Cycle Divisions • Preswing – The lower limb is positioned to quickly swing forward beneath the advancing body – The body weight is unloaded from one limb and transferred to the opposite limb – Toe-off

Preswing • Transitional period of double support • Limb is uploaded and prepared to swing • Begins with initial contact of contralateral limb and ends with toeoff of stance limb

Cycle Divisions • Swing phase – Begins as soon as the toes leave the surface and terminates when the limb next makes contact with the surface – Momentum gained at toe-off helps carry leg through the swing phase – Consists of three phases

Cycle Divisions • Initial swing – The foot is pushed off the ground – The limb is accelerated forward helping to provide the force to sustain forward body movement – Femur advances – Ankle dorsiflexes, allowing toe clearance – Subtalar joint - pronation

Cycle Divisions • Midswing – The limb passes beneath the body to where the tibia is vertical – CG directly over opposite supporting foot – Propulsion continues – Talocrural joint – dorsiflexed to neutral or slight dorsiflexion

Cycle Divisions • Terminal swing – The limb decelerates forward motion in preparation for the initial contact (IC) of the stance to initiate a new step – Subtalar joint – supination – Foot supinated and positioned for foot strike

CG Excursion • Pelvic Rotation • Pelvic lateral tilt + drop • Knee, Ankle and foot interaction

Pelvic Rotation - Pelvic moves fwd with swing limb - Trials behind with the following limb - Flattens the arc of CM motion by increasing the effective leg-length at these times

Pelvic Lateral Tilt and Drop

Stance Knee Flexion - Shortens the leg during stance - Flexion at the beginning and end of stance smoothes the abrupt changes in CG - Flattens the arc

Pre-Requisites of Good Gait • Stability in stance • Foot clearance in swing • Pre-positioning of the foot • Adequate step length • Energy conservation

Stability in Stance • High neuro-muscular control required in single support phase of gait • Use of walking aids if neuro-muscular status is compromised – creates triangular base

Adequate Step Length • Ensures correct flow of momentum • Correct distribution of weight which helps with balance

Shock Absorption • 90% shock absorbed by quadriceps contraction during the weight acceptance phase of gait • 10% from: – Fat pad/ligaments providing elastic property and rheology (useful when 60% BW falls on heel at initial contact)

Shock Absorption – Synovial fluid with its viscoelatic properties which allow it to dissipate forces – Cartilage and Capsules absorbing synovial fluid – Bone trabecular formations and ability to bend

Forces • The principal forces are: – Body weight (BW) – Ground reaction force (GRF) – Muscle force (MF)

Body Weight • Always acts vertically downwards from the CG • If its line of action does not pass through a joint, it will produce a torque about that joint • The torque will cause rotation at the joint unless it is opposed by another force (e.g. muscle, or ligament) • BW contributes to GRF

Ground Reaction Forces (GRF) • “Reaction” force • Forces exerted between the body and the ground during ambulation • GRFs are composed of vector forces acting in vertical, fore-aft, and mediallateral directions

Ground Reaction Force • Push exerted by ground on foot, as a consequence of Newton’s 3rd Law. • Equal magnitude, opposite direction, same point of application as action force. • If line of the reaction force does not pass through a joint, it will produce a torque about that joint

Muscle force • • • • •

Contribute to ground reaction force Ensure balance Increase energy economy Allow flexible gait patterns Slow down and/or prevent limb movements

Muscle Activity in the Gait Cycle

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Muscle Activity in the Gait Cycle Stance Phase: • The gluteus maximus and hamstrings extend the hip early in the stance phase • The hip flexors check this movement before toe-off • The gluteus medius and minimus abduct the hip • The hip medial rotators act in the first half of the stance phase • Late in the stance phase the adductors and lateral rotators check the momentum generated by the former muscles

Muscle Activity in the Gait Cycle Stance Phase: • The quadriceps femoris acts at the beginning of the stance phase extending the knee • The hamstrings flex the knee just before toe-off • The dorsiflexors of the foot act immediately after heel strike to check plantar flexion under the force of gravity and bring the foot into full contact with the ground

Muscle Activity in the Gait Cycle Stance Phase: • The plantar flexors act throughout the second half of the stance phase powering the forward thrust of the body using the thigh and leg as a single unit • The body is powered forward by the plantar flexors and hip extensors • As the body weight comes onto the foot the intrinsic foot muscles contract to support the plantar ligaments

Muscle Activity in the Gait Cycle Swing Phase: • The hip flexors already function at the end of the stance phase continue into early swing phase along with the adductors and lateral rotators • They are essentially silent in midswing relying on momentum of the thigh mass to bring the thigh forward

Muscle Activity in the Gait Cycle Swing Phase: • Thigh momentum is checked at the end of the swing phase by the hip extensors • The hamstrings function late in the stance phase and continue into early swing phase to flex the knee • The forward momentum of the limb in the swing results in the transition from flexion to extension at the knee with some assistance from the quadriceps muscles

Muscle Activity in the Gait Cycle • This momentum is checked by the hamstrings prior to heel strike • Dorsiflexors and the ankle act throughout the swing phase

Muscle Activity in the Gait Cycle

Eccentric Concentric

Muscle Activity in the Gait Cycle • Pretibial Muscles – Anterior tibial, EDL, EHL – Prior to and during heel strike • Eccentric contraction - lowers foot to the ground

– Prior to and during preswing • Concentric contraction – DF foot, clear toes off ground

• Calf Muscles – Gastrocs, Soleus (FDL, FHL, Posterior tibial) – Foot flat • Eccentric contraction - control of tibia over the foot

– Heel off • Concentric contraction – ankle plantarflexion

Muscle Activity in the Gait Cycle • Quadriceps – Vastus medialis/lateralis/intermedius, RF – Before Heel Strike • Concentric contraction – initiate knee extension

– Swing phase • Eccentric contraction – slow down leg (tibia)

• Hamstrings – Biceps, Semitendinosus, Semimembranosus – Heel strike • Eccentric contraction - HS peaks – protects knee from hyperextension

– Swing phase • Concentric contraction – knee flexion, hip extension

Muscle Activity in the Gait Cycle • Hip Abductors – Gluteus medius, Gluteus minimus, TFL – Stance phase • Concentric contraction - stabilize pelvis

• Hip Adductors – Adductor longus/brevis, Gracilis, Adductor magnus (horizontal and vertical heads) – Early and late stance • Concentric contraction –stabilize pelvis

Muscle Activity in the Gait Cycle • Gluteus Maximus – Stance phase • Eccentric contraction – decelerate forward momentum – Pre-Swing phase • Concentric contraction – hip extension

• Erector Spinae – Heel strike through Toe-off – Maintain trunk posture

• Foot Intrinsics – Stance phase • Concentric contraction – support plantar fascia