Muscle Activity During Gait

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Top Contributors - Wanda van Niekerk, Jess Bell and Lucinda hampton  

Breakdown of Gait Cycle Sub-Phases

Initial Contact (or Heel Strike) - 0%

The moment the foot touches the ground and begins the first phase of double support. Its function is to establish contact with the ground surface and initiate weight acceptance.

Kinetics at Initial Contact

Joint	Kinetics
Ankle	External forces	Internal forces/ Muscle Action
	GRF posterior to axis of ankle joint External plantar flexion moment created	Internal dorsiflexion moment Eccentric contraction of dorsiflexors: tibialis anterior extensor digitorum longus extensor hallucis longus
Knee	GRF anterior to axis of knee joint External extensor moment created	Internal flexion moment Concentric contraction of knee flexors: hamstrings Eccentric contraction of knee extensors: quadriceps (range of motion change in knee 0° - 15°, this results in the shifting of GRF from anterior to posterior - this will result in external flexor torque and knee extensors will work eccentrically to control the knee)
Hip	GRF anterior to axis rotation of hip joint External moment created	Concentric contraction of gluteal muscles (hip extensors): gluteus maximus

Foot Flat (Loading Response) - 0-10%

Begins with initial contact and continues until the contralateral foot leaves the ground. The foot continues to accept weight and absorb shock by rolling into pronation.

Kinetics at Foot Flat

Joint	Kinetics
	External forces	Internal forces/Muscle Action
Ankle	GRF posterior to axis of rotation of ankle joint External plantar flexion torque created	Concentric contraction of dorsiflexors Eccentric contraction of plantar flexors: gastrocnemius soleus Range of motion change in ankle 5° plantarflexion to 5° dorsiflexion, results in the shifting of GRF from posterior to anterior thus posterior musculature (plantarflexors) are used eccentrically to control dorsiflexion
Knee	GRF posterior to axis of rotation of knee joint External flexion torque created	Concentric contraction of knee extensors
Hip	GRF anterior to axis of rotation of hip joint	Concentric contraction of hip extensors

Midstance - 10-30%

Begins when the contralateral foot leaves the ground and continues until ipsilateral heel lifts off the ground. The body is supported by a single leg and begins to move from force absorption at impact to force propulsion forward.

Kinetics at Midstance

Joint	Kinetics
	External forces	Internal forces/Muscle Actions
Ankle	GRF anterior to axis of rotation of ankle External dorsiflexion torque	Concentric contraction of plantarflexors
Knee	GRF anterior to axis of rotation of knee joint External extension torque	Eccentric contraction of knee flexors
Hip	GRF posterior to axis of rotation	Eccentric contraction of hip flexors

Terminal Stance (or Heel Off) - 30-50%

Begins when the heel leaves the floor and continues until the contralateral foot contacts the ground. In addition to single limb support and stability, this event serves to propel the body forward. Bodyweight is divided over the metatarsal heads.

	Kinematics/Joint Motion	Muscle Action
Ankle	Gradual dorsiflexion until a maximum of 10° before beginning to plantarflex	Eccentric plantarflexors, then concentric plantarflexors
Knee	Continues extending until a maximum of 5° of flexion before beginning to flex	Concentric extensors, then eccentric extensors and concentric flexors
Hip	Extends until a maximum of 10° extension	Eccentric flexors

Pre-Swing (or Toe Off) - 50-60%

Begins when the contralateral foot contacts the ground and continues until the ipsilateral foot leaves the ground. Provides the final burst of propulsion as the toes leave the ground.

	Kinematics/Joint Motion	Muscle Action
Ankle	Begins to plantarflex rapidly before foot leaves the ground	Concentric plantarflexors
Knee	Begins to flex rapidly	Eccentric extensors
Hip	Begins to flex before foot leaves the ground	Concentric flexors

Early Swing - 60-75%

Begins when the foot leaves the ground until it is aligned with the contralateral ankle. This event functions to advance the limb and shorten the limb for foot clearance.

	Kinematics/Joint Motion	Muscle Action
Ankle	Continues to plantarflex until a maximum of 20° before moving back towards a neutral position	Eccentric dorsiflexors, then concentric dorsiflexors and eccentric plantarflexors
Knee	Rapid knee flexion until a maximum of about 60°	Eccentric extensors and concentric flexors
Hip	Gradually flexes	Concentric flexors

Mid-Swing - 75-85%

Begins from the ankle and foot alignment and continues until the swing leg tibia is vertical. As in early swing, it functions to advance the limb and shorten the limb for foot clearance.

	Kinematics/Joint Motion	Muscle Action
Ankle	Maintains a neutral position	Concentric dorsiflexors
Knee	Begins to extend	Eccentric flexors
Hip	Continues to flex until a maximum of just over 30°	Concentric flexors

Late Swing/Deceleration - 85-100%

Begins when the swing leg tibia is vertical and ends with initial contact. Limb advancement slows in preparation.

	Kinematics/Joint Motion	Muscle Action
Ankle	Maintains a neutral position	Concentric dorsiflexors
Knee	Extends until full extension, and flexes just slightly before initial contact	Eccentric flexors, then concentric flexors
Hip	Hip remains flexed to around 30 °	Concentric flexors and eccentric extensors, then concentric extensors

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