Gait Analysis

1. Gait Definition

• Gait is the sequence of limb motions used to move the body forward while maintaining stability.
• During walking gait, one foot is always in contact with the ground; both feet are never off the ground simultaneously.
• It involves reciprocal floor contact patterns: one limb supports the body while the other advances, then roles reverse.
• Body weight transfer occurs with both feet in contact at some points, ensuring balance.

2. Relevance of Gait

• Gait is essential for locomotion and has a high functional impact on daily life.
• It is involved in day-to-day tasks, work environments, and sports/recreation.
• Deficits in gait can have a high impact on mobility and independence.
• Gait affects energy expenditure, influencing overall physical efficiency.

3. When to Analyze Gait

Gait analysis is crucial in various contexts, including:

Key point: Gait is a coordinated, stable, and energy-efficient pattern of limb movements essential for functional mobility and quality of life.

1. Gait Cycle Phases and Terminology

The gait cycle is the sequence of motions that occur from one initial contact of a foot to the next initial contact of the same foot. It consists of two main phases:

• Stance phase includes:
  • Single stance (40%): only one foot on the ground
  • Double stance (20%): both feet on the ground

2. Terminology Variations for Gait Phases

3. Spatiotemporal Parameters of Gait

Gait analysis involves measuring temporal and spatial parameters to assess rhythm, efficiency, and movement patterns.

• Temporal parameters: time-related measures (e.g., duration of phases)
• Spatial parameters: distance-related measures (e.g., step length, stride length)

4. Key Spatial Parameters

To remember:
One gait cycle equals one stride, which consists of two steps (one with each foot).

1. Spatial Parameters

• Walking base (base of support): lateral distance between the lines of the two feet, measured at the midpoint of the back of the heel or below the center of the ankle joint.
• Toe out angle (º): angle between the direction of progression and a reference line on the sole of the foot.

2. Temporal Parameters

• Stride time (s): duration of a full gait cycle (two steps).
• Step time (s): duration of a single step.
• Swing time (%): percentage of the gait cycle when the foot is in the air advancing forward.
• Stance time (%): percentage of the gait cycle when the foot is in contact with the floor, starting at initial contact.
• Single support (%): percentage of the gait cycle when only one foot contacts the floor; best index of limb support capability.
• Double support (%): percentage of the gait cycle when both feet contact the floor simultaneously.

3. Definitions of Gait Phases

4. Cadence and Cycle Time

• Cadence (steps/min): number of steps taken per minute.
• Cycle time (stride time, s): time for one full stride cycle.

Relationship between cadence and cycle time:

$$\text{cycle time (s)} = \frac{120}{\text{cadence (steps/min)}}$$

5. Relationship Between Stride Length and Cadence at Constant Speed

Key point: Walking speed is the product of stride length and cadence; adjusting one affects the other to maintain speed.

1. Velocity (Speed) in Gait

• Velocity (m/s) = distance covered by the whole body in a given time.
• Two formulas to calculate velocity:
  • $\text{speed} = \frac{\text{stride length (m)} \times \text{cadence (steps/min)}}{120}$
  • $\text{speed} = \frac{\text{stride length (m)}}{\text{cycle time (s)}}$

2. Key Spatiotemporal Parameters of Gait

3. Step Length

• Step length: Distance between successive heel strikes of opposite feet.
• Typical adult value: 70–80 cm.
• Shorter step length may indicate pathology or weakness.

> Velocity in gait is a product of stride length and cadence, and changes in spatiotemporal parameters reflect clinical conditions such as weakness, pain, or neurological disorders.

1. Key Temporal Parameters in Gait Analysis

2. Gait Development Across Lifespan

• Gait capacity matures around 7 years old.
• Step width decreases with age as balance improves.
• Cadence decreases while step length and walking speed increase with age.

3. Gait Changes in Older Adults

• Preferred walking speed decreases by 12–20%.
• Stance time increases to approximately 63% of the gait cycle.
• Step length and single support time decrease.
• Double support time increases by 18–26%.
• Decline in ankle plantarflexor function, hip extension, and flexion capacity.

To remember: Stride length and walking speed decrease with age and pathology, while base of support and double support time increase to compensate for balance and stability issues.

1. Gait Parameters Across the Lifespan

Gait parameters evolve throughout life, reflecting changes in motor control, strength, and biomechanics.

a) Key Spatiotemporal Parameters

b) Joint Angles and Movements

• Joint angles refer to the angle between proximal and distal segments (hip, knee, ankle).
• Movements are analyzed in Open Kinematic Chain (OKC) and Closed Kinematic Chain (CKC) contexts.
• Major joint movements occur primarily in the sagittal plane during gait phases.

c) Gait Cycle Overview

• Defined as the period from heel strike to the next heel strike of the same foot.
• Divided into phases: stance (foot on ground) and swing (foot in air).
• Each phase has characteristic joint angles and muscle activations.

d) Stance Phase Subdivisions and Objectives

To remember: Gait parameters such as speed, cadence, and step width change systematically with age, reflecting adaptations in balance and motor control. Joint angles during gait phases remain consistent but may vary in amplitude across the lifespan.

1. Joint Angles During Gait Cycle

The gait cycle is divided into phases where joint angles of the hip, knee, and ankle change to enable efficient locomotion. Focus is often on the stance phase of the gray limb.

a) Key Joint Movements Summary

• Hip: Starts flexed during loading, extends through mid and terminal stance to prepare for swing.
• Knee: Flexed initially, then extends during stance to support body weight.
• Ankle: Brief plantar flexion at loading, dorsiflexes during mid and terminal stance to control forward progression.

During the stance phase, joint angles transition to support body weight, maintain stability, and prepare the limb for the swing phase.

1. Stance Phase Joint Movements

During the stance phase (50–62% of the gait cycle), the key joint positions are:

This phase involves the foot being in contact with the ground, supporting body weight.

2. Pre-Swing Phase (50–62% of GC)

• Hip: Less extended than stance
• Knee: Flexed
• Ankle: Plantar flexion

This phase prepares the limb for the swing phase by unloading the foot.

3. Swing Phase Overview

The swing phase occurs when the foot is off the ground and is divided into three sub-phases:

1. Initial Swing (62–75% of GC)
2. Mid Swing (75–87% of GC)
3. Terminal Swing (87–100% of GC)

Main task: Advancement of the swing limb.

4. Initial Swing (62–75% of GC)

• Begins: Foot lifts off the ground.
• Ends: Swinging foot is opposite the stance foot.
• Duration: One third of the swing phase.

Objectives:

• Clear the foot from the floor.
• Advance the limb from its trailing position.

Joint Movements:

5. Mid Swing (75–87% of GC)

• Begins: Swing foot opposite stance foot.
• Ends: Swing limb forward with vertical tibia.

Objectives:

• Continue limb advancement.
• Maintain foot clearance.

Joint Movements:

6. Terminal Swing (87–100% of GC)

• Begins: Vertical tibia position.
• Ends: Foot strikes the floor.

Joint Movements:

• Prepare for initial contact with the ground (not detailed here).

Key point: During the swing phase, the hip moves from extended to flexed, the knee remains flexed, and the ankle transitions from plantar flexion to dorsiflexion to ensure foot clearance and limb advancement.

1. Swing Phase Joint Movements

The swing phase completes limb advancement and prepares the limb for the next stance phase. Key joint movements occur primarily in the sagittal plane, with important contributions in frontal and transverse planes.

a) Hip Movements

b) Knee Movements

• Sagittal plane: Flexed during swing to allow foot clearance.
• Frontal plane: Stable with minimal movement; knee is slightly unlocked.
• Transverse plane: Small external rotation following hip rotation.

c) Ankle and Subtalar Joint Movements

d) Pelvis Movements

• Sagittal plane: Small movements close to neutral.
• Frontal plane: 10–15° movement coordinated with hip abduction/adduction.
• Transverse plane: Internal and external rotations related to step length.

e) Trunk and Head

• Serve as a reference for posture and movement control during upright gait.
• Together, the head and trunk represent more than 50% of body weight, influencing balance and coordination.

To remember: The swing phase involves coordinated flexion at the hip and knee, dorsiflexion at the ankle, and controlled movements in frontal and transverse planes to ensure smooth limb advancement and prepare for stance.

1. Trunk and Pelvis Movements

• The trunk acts as a key stability promoter during gait, serving as the central axis for both upper and lower limb movements.
• It functions like an inverted-pendulum model, allowing controlled oscillations that aid balance.
• Pelvis and trunk movements vary depending on the gait phase and environmental conditions, adapting dynamically to maintain stability.

2. Upper Limb Movements: Arm Swing

• Arm swing is an active movement, driven by muscle activation, not passive momentum.
• Importance of arm swing:
  • Optimizes gait stability
  • Minimizes energy consumption
• Mechanisms involved:
  • Muscle activation
  • Shoulder acceleration
  • Inertia effects

3. Muscular Activation and Segment Behavior in Gait

• Gait involves dynamic stability, meaning muscles and body segments are never completely static.
• Segments can be classified by their behavior during gait:

4. Integrative Approach to Muscle Biomechanics in Gait

Understanding muscle function during gait requires integrating:

• Motor control
• Motor learning
• Biomechanics
• Muscle function
• Muscular synergism

This integration is essential to analyze the muscular activation patterns throughout the gait cycle.

5. Example: Initial Contact Phase

• Hip: Flexion with a small movement toward extension
• Knee: Extended but not locked
• Ankle: Dorsiflexed to neutral position

Key point: The trunk and pelvis provide a dynamic, stable base for limb movements, while arm swing actively contributes to gait efficiency and stability through muscle-driven motion.

1. Muscle Activation During Gait

Muscle activation during gait varies according to the phase of the gait cycle and the joint involved (hip, knee, ankle). Muscles act concentrically, eccentrically, or isometrically to control movement and stabilize the body.

2. Initial Contact & Loading Response

• Body weight is transferred onto the forward limb.

3. Mid Stance

• Contralateral foot is lifted, body weight aligned over forefoot.

4. Summary of Key Muscle Roles During Gait Phases

> Muscle activation during gait is phase-dependent, with extensors and stabilizers acting concentrically or eccentrically to control joint motion and maintain balance.

1. Phases of Gait and Muscle Activation

Gait is divided into distinct phases, each characterized by specific joint positions and muscle activations essential for efficient locomotion.

2. Key Biomechanical Principles in Gait

• Muscle Activation Patterns: Different muscle groups activate concentrically or eccentrically depending on the phase to control limb movement and maintain stability.
• Joint Positioning: Hip, knee, and ankle positions change systematically to optimize energy efficiency and forward propulsion.
• Weight Transfer: Abrupt transfer of body weight occurs during pre-swing, preparing the limb for toe-off and swing phase initiation.
• Foot Clearance: Dorsiflexors are crucial during swing phases to lift the foot and prevent tripping.

To retain: Each gait phase involves a coordinated pattern of joint angles and muscle activations that ensure smooth, stable, and efficient walking.

1. Ground Reaction Forces in Gait

Ground Reaction Force (GRF) is the force exerted by the ground on the body during walking, crucial for understanding gait mechanics.

2. Key Phases of Gait & Muscle Activation

3. Muscle Actions During Stance Phase

• Hip Extensors: Act concentrically during early loading response to extend the hip.
• Hip Abductors: Stabilize the coxofemoral joint laterally during stance.
• Quadriceps: Control knee flexion eccentrically during weight acceptance; extend knee concentrically through early midstance.
• Tensor Fascia Lata: Posterior fibers activate at loading response onset; anterior fibers activate later into terminal stance.

4. Ankle Movement & Muscle Control

To remember: Ground reaction forces reflect the interaction between the limb and ground, with muscle groups activating in a coordinated sequence to control limb position, absorb impact, and propel the body forward during gait.

1. Instrumented Gait Analysis Methods

a) Gait Cycle Phases

• Stance Phase (0-62%)

  • Initial Contact (0-2%)
  • Loading Response (2-12%)
  • Mid Stance (12-31%)
  • Terminal Stance (31-50%)
  • Pre Swing (50-62%)

• Swing Phase (62-100%)

  • Initial Swing (62-75%)
  • Mid Swing (75-87%)
  • Terminal Swing (87-100%)

b) Muscle Activation Patterns During Gait

c) Key Functional Roles

• Hip flexors: Propel the limb forward in swing initiation.
• Hip adductors and hamstrings: Stabilize and control limb during stance-swing transitions.
• Knee flexors (hamstrings, gracilis, sartorius): Facilitate knee flexion during swing for foot clearance.
• Ankle dorsiflexors: Active concentrically in swing to dorsiflex the foot, preventing toe drag.
• Ankle plantarflexors: Act eccentrically during stance to control forward tibial progression.

To remember: Muscle activation during gait is phase-specific and coordinated to ensure smooth limb advancement and stability, with hip flexors initiating swing and ankle dorsiflexors ensuring foot clearance.

d) Summary Table of Muscle Activation by Gait Phase

e) Spatiotemporal Parameters (Overview)

• Instrumented gait analysis measures timing, joint angles, and muscle activation to assess gait quality.
• Typical gait cycle is divided into stance and swing phases, each with sub-phases critical for muscle coordination.

This concise framework of muscle activation and gait phases is essential for interpreting instrumented gait analysis data and understanding normal and pathological gait patterns.

1. Common Gait Abnormalities and Clinical Cases

a) Key Gait Determinants Throughout the Gait Cycle

Gait is governed by coordinated movements of the pelvis, hip, knee, and ankle joints, which optimize step length and energy efficiency. The main determinants are:

b) Summary of Joint Movements by Gait Phase

• Pelvic rotation: Alternates between forward (medial) and backward (lateral) rotation to increase step length and smooth movement.
• Hip: Cycles between flexion and extension to propel and prepare the leg for the next step.
• Knee: Flexes during swing for foot clearance and extends during stance for support.
• Ankle: Moves from dorsiflexion (lifting foot) to plantarflexion (push-off) and back to dorsiflexion for clearance.

Key point: Efficient gait depends on the precise timing and amplitude of pelvic rotation combined with coordinated hip, knee, and ankle joint movements.

c) Clinical Relevance

• Abnormalities in any determinant (e.g., reduced pelvic rotation, limited hip flexion, or impaired dorsiflexion) can cause gait deviations.
• Understanding these determinants helps diagnose specific gait pathologies and tailor rehabilitation strategies.

This concise overview of gait determinants provides the essential framework to analyze common gait abnormalities and clinical cases.

1. Running Cycle and Biomechanics

a) Ground Reaction Forces (GRFs) in Running

• GRFs vary in direction and intensity throughout the running cycle, changing vector orientation relative to each joint.
• GRFs are three-dimensional:
  • Vertical component: related to weight acceptance (absorption) and push-off (propulsion).
  • Anteroposterior component: controls braking (deceleration) and propulsion (acceleration).
  • Medio-lateral component: manages side-to-side balance by controlling center of mass displacement, linked to hip adduction during stance phase.

b) Key Phases and Forces

• Toe-off occurs at approximately 57% of the running cycle, marking transition from stance to swing phase.

c) Joint Biomechanics and Force Interaction

• At each joint (e.g., knee), the torque generated depends on:
  • The magnitude of the GRF.
  • The lever arm, i.e., the perpendicular distance between the GRF vector and the joint axis.
  • The joint angle, which influences lever arm length and force direction.
• This interaction produces joint moments (torques) critical for movement control and stability.

d) Instrumented Gait Analysis

• Combines video capture and instrumented measurements (force plates, motion sensors) to quantify:
  • Joint angles
  • GRFs in 3D
  • Timing of gait phases
• Provides detailed reports for clinical or research use, enabling precise assessment of running biomechanics.

Key point: Ground reaction forces are vector quantities that change in magnitude and direction during running, directly influencing joint torques and overall gait mechanics.

1. Running Joint Angles

Running involves distinct joint angle patterns compared to walking, characterized by greater ranges of motion to accommodate higher speed and impact.

• Hip: Greater flexion during swing to advance the leg and extension during propulsion.
• Knee: High flexion during swing allows foot clearance; moderate flexion during stance absorbs shock.
• Ankle/Foot: Dynamic plantarflexion at toe-off and dorsiflexion at initial contact manage ground reaction forces.

2. Foot Strike Patterns in Running

Foot strike refers to the part of the foot that first contacts the ground during running. It influences joint angles, loading patterns, and injury risk.

Key point: Running joint angles and foot strike patterns are adapted to optimize propulsion and shock absorption, influencing performance and injury risk.

3. Running Cycle Phases and Joint Behavior

• Contact Phase: Foot strikes the ground; joints absorb impact.
• Braking Phase: Deceleration occurs; knee flexion increases to absorb force.
• Propulsion Phase: Extension of hip, knee, and ankle generates forward thrust.
• Flight Phase: No ground contact; joints prepare for next step with flexion to clear the ground.

Understanding these joint angles and foot strike types is essential for analyzing running mechanics and addressing gait abnormalities or optimizing performance.

1. Running Ground Reaction Forces (GRF)

Ground Reaction Force (GRF) during running varies significantly depending on the foot strike pattern and footwear.

2. Foot Strike Types

3. GRF Characteristics by Foot Strike

4. Phases of Running GRF

1. Braking Phase

   • Occurs immediately after foot contact
   • GRF vector directed backward relative to the runner
   • Decelerates forward motion

2. Acceleration Phase

   • Follows braking phase
   • GRF vector directed forward
   • Propels the runner forward

5. Key Quantitative Observations

• Force magnitude can exceed 2 to 3 times body weight during running.
• Rearfoot strike shows a distinct initial impact peak in GRF, associated with heel contact.
• Forefoot strike produces a more gradual force increase, reducing impact transient.
• Footwear modifies GRF magnitude but not the fundamental pattern of foot strike.

To remember:
The foot strike pattern (rearfoot vs. forefoot) fundamentally alters the shape and magnitude of the running ground reaction force, influencing impact loading and injury risk.