Muscle Activity During Gait

Original Editor - Wanda van Niekerk based on the course by Alexandra Kopelovich
Top Contributors - Wanda van Niekerk, Jess Bell and Lucinda hampton  

Gait Kinetics and Joint Moment

Gait kinetics investigates the forces and moments of the gait cycle. This includes the study of ground reaction forces (GRF), joint torque, plantar pressure distribution and muscle activity. The body should be in equilibrium during gait, therefore, the external ground reaction forces (GRF) (external moment) should be balanced by the internal muscle forces (internal moment). Different muscles perform different actions at every phase to create an internal moment against the external joint moment. Ground reaction force vectors create the direction of moment and the muscle will act in the opposite direction. If the ground reaction force falls anterior to the axis of the joint, the proximal segment of the joint will move anteriorly; if the ground reaction force falls posterior to the axis of the joint, the proximal segment of the joint with move posteriorly. Muscles can contract concentrically or eccentrically to overcome the external moment. During a concentric muscle contraction, the muscle shortens and there is movement at the joint, whereas during an eccentric contraction the muscle lengthens while producing force.

Read more:

• Types of Skeletal Muscle Actions
• Ground Reaction Forces

Breakdown of Kinematics and Kinetics During the Gait Cycle

Stance Phase

Initial Contact (or Heel Strike)

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.

Kinematics and Kinetics at Initial Contact

Joint	Kinematics	Kinetics
		External Forces	Internal Forces/ Muscle Action
Ankle	Ankle moves from 0° neutral at initial contact to 5° of plantarflexion at foot flat	GRF posterior to axis of rotation of the ankle joint External plantar flexor moment created	Internal dorsiflexor moment Eccentric contraction of dorsiflexors (tibialis anterior, extensor digitorum longus, extensor hallucis longus)
Knee	Knee moves from 0° extension at initial contact to 15° flexion at foot flat	GRF anterior to axis of rotation of the knee joint External extensor moment created	Internal flexor moment Concentric contraction of knee flexors (hamstrings) Eccentric contraction of knee extensors (quadriceps) The range of motion change in the knee joint (0° - 15°), results in the shifting of GRF from anterior to posterior - this will result in external flexor torque, and the knee extensors will work eccentrically to control the knee
Hip	Hip moves from 20° flexion at initial contact to 15° of flexion at foot flat	GRF anterior to axis of rotation of the hip joint External flexor moment created	Internal extensor moment Concentric contraction of hip extensors (gluteus maximus)

Foot Flat (Loading Response)

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.

Kinematics and Kinetics at Foot Flat

Joint	Kinematics	Kinetics
		External Forces	Internal Forces/Muscle Action
Ankle	Ankle moves from 5° of plantarflexion during foot flat to 5° of dorsiflexion at midstance	GRF posterior to axis of rotation of ankle joint External plantar flexor moment created	Internal dorsiflexor moment Concentric contraction of dorsiflexors Eccentric contraction of plantarflexors (gastrocnemius, soleus) The range of motion change in the ankle from 5° plantarflexion to 5° dorsiflexion results in the shifting of GRF from posterior to anterior, thus the posterior musculature (plantarflexors) is used eccentrically to control dorsiflexion.
Knee	Knee moves from 15° flexion at foot flat to 5° flexion at midstance	GRF posterior to axis of rotation of the knee joint External flexor moment created	Internal extensor moment Concentric contraction of knee extensors
Hip	Hip moves from 15° flexion at foot flat to 0° at midstance	GRF anterior to axis of rotation of the hip joint External flexor moment created	Internal extensor moment Concentric contraction of hip extensors

Midstance

Begins when the contralateral foot leaves the ground and continues until the 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.

Kinematics and Kinetics at Midstance

Joint	Kinematics	Kinetics
		External Forces	Internal forces/Muscle Actions
Ankle	Ankle moves from 5° dorsiflexion at midstance to 0° of dorsiflexion at heel off	GRF anterior to axis of rotation of the ankle External dorsiflexor moment	Internal plantarflexor moment Concentric contraction of plantarflexors
Knee	Knee moves from 5° flexion at midstance to 0° flexion at heel off	GRF anterior to axis of rotation of the knee joint External extensor moment	Internal flexor moment Eccentric contraction of knee flexors
Hip	Hip moves from 0° flexion at midstance to 10° - 20° of extension at foot flat	GRF posterior to axis of rotation of the hip joint External extensor moment	Internal flexor moment Eccentric contraction of hip flexors (iliopsoas)

Heel Off (or Terminal Stance)

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 and Kinetics at Heel Off

Joint	Kinematics	Kinetics
		External Forces	Internal Forces/Muscle Actions
Ankle	Ankle moves from 0° at heel off to 20° plantarflexion at toe off	GRF anterior to the axis of rotation of the ankle External dorsiflexor moment	Internal plantarflexor moment Concentric contraction of plantarflexors
Knee	Knee moves from 0° at heel off to 30° flexion at toe off	GRF anterior to the axis of rotation of the knee External extensor moment	Internal flexor moment Concentric contraction of knee flexors
Hip	Hip moves from 10° extension at heel off to 20° extension at toe off	GRF posterior to the axis of rotation of the hip joint External extensor moment	Internal flexor moment Eccentric contraction of hip flexors

Toe Off (or Preswing)

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 and Kinetics at Toe Off

Joint	Kinematics	Kinetics
		External Forces	Internal Forces/Muscle Actions
Ankle	Ankle moves from 20° plantarflexion at toe off to 10° plantar flexion at early swing	GRF anterior to the axis of rotation of the ankle joint External dorsiflexor moment	Internal plantarflexor moment Eccentric contraction of plantarflexors Concentric contraction of dorsiflexors to propel the foot up
Knee	Knee moves from 30° flexion at toe off to 60° flexion at early swing	GRF posterior to the axis of rotation of the knee joint External flexor moment	Internal extensor moment Eccentric contraction of knee extensors Concentric contraction of knee flexors
Hip	Hip moves from 10° - 20° extension at toe off to 20° flexion at early swing	GRF posterior to the axis of rotation of the hip joint External extensor moment	Internal flexor moment Concentric contraction of hip flexors

Swing Phase

Ground reaction forces are not applicable to the swing phase as there is no contact with the ground. However, the muscles still contract concentrically or eccentrically as needed.

Early Swing

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.

Muscle Actions at Early Swing

	Kinematics/Joint Motion	Muscle Action
Ankle	Ankle moves from 20° of plantarflexion at toe off to 10° of plantarflexion at early swing	Concentric contraction of dorsiflexors
Knee	Knee moves from 30° flexion at toe off to 60° flexion at early swing	Eccentric contraction of knee extensors and concentric contraction of knee flexors
Hip	Hip moves into flexion	Concentric contraction of hip flexors

Mid-Swing

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

Muscle Action at Mid-Swing

	Kinematics/Joint Motion	Muscle Action
Ankle	Ankle moves from 10° of plantarflexion at early swing to 0° of plantarflexion at mid-swing	Concentric contraction of dorsiflexors
Knee	Knee moves from 60° flexion at early swing to 30° flexion at mid-swing	Eccentric contraction of knee flexors
Hip	Hip moves from 20° flexion at early swing to 30° flexion at mid-swing	Concentric contraction of hip flexors

Late Swing/Deceleration

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

Muscle Action at Late Swing

	Kinematics/Joint Motion	Muscle Action
Ankle	Maintains a neutral position	Concentric and isometric contraction of dorsiflexors
Knee	Knee moves from 3o° flexion at mid-swing to o° flexion at late swing	Eccentric contraction of knee flexors, then concentric contraction of knee flexors
Hip	Hip moves from 20°-30° flexion at mid-swing to 30° flexion at late swing	Concentric contraction of hip flexors