The Gait Cycle

Original Editor - Karsten De Koster Top Contributors - Daphne Xuan and Tarina van der Stockt

The Gait Cycle

The action of walking may be summarised by the following sequence:

1. Registration and activation of the gait command within the central nervous system.
2. Transmission of gait signals to the peripheral nervous system.
4. Contraction of muscles.
5. Generation of forces across joints
6. Regulation of joint forces and moments by skeletal segments.
7. Generation of ground reaction forces (GRF).

Normal gait consists of two phases: stance phase; swing phase. These phases are further divided into a total of 8 sub-phases. The gait cycle involves a combination of open- and closed-chain activities.

Stance Phase

The stance phase occupies 60% of the total gait cycle, during which some part of the foot is in contact with the ground. It is further divided into five sub-phases:

1. Initial contact (heel strike)
2. Loading response (foot flat)
3. Mid-stance
4. Terminal stance (heel off)
5. Pre-swing (toe off)

Swing Phase

The swing phase occupies 40% of the total gait cycle , during which the foot is not in contact with the ground and the bodyweight is borne by the other leg and foot. It is further divided into three sub-phases:

1. Initial swing
2. Mid-swing
3. Late swing

In a complete two-step cycle both feet are in contact with the ground at the same time for 20% of the total gait cycle, 10%at the beginning of the stance phase and 10% at the end of the stance phase. These are termed 'double-support periods'. The rest of the time is spent in single support, when only one foot is in contact with the ground.

The 90-second video below gives the basics of this cycle:

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.

	Kinematics/Joint Motion	Muscle Action
Ankle	Neutral, 0°	Concentric to eccentric dorsiflexors
Knee	5° flexion	Eccentric extensors
Hip	30° flexion	Concentric extensors and eccentric flexors

Loading Response (or Foot Flat) - 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.

	Kinematics/Joint Motion	Muscle Action
Ankle	Rapid plantarflexion to 10°	Eccentric dorsiflexors
Knee	Flexes to 10-15°	Eccentric extensors and concentric flexors
Hip	Gradual extension	Concentric 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.

	Kinematics/Joint Motion	Muscle Action
Ankle	Gradual dorsiflexion	Eccentric plantarflexors and concentric dorsiflexors
Knee	Begins to extend	Concentric extensors
Hip	Gradual extension	Concentric extensors

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

Clinical Application

Understanding the gait cycle allows for effective gait analysis. When analysing gait, it should be done systematically, looking at each joint separately throughout the entire gait cycle and detecting deviations from normal. Injury or disease can alter any of the sub-phases of the gait cycle, resulting in distinct characteristics of the gait pattern.