⛹️‍♂️Motor Learning and Control Unit 15 – Gait and Locomotion

Key Concepts and Definitions

• Gait refers to the manner or pattern of walking or running, involving the coordination of the musculoskeletal system
• Locomotion is the act of moving from one place to another, which includes walking, running, and other forms of movement
• Stride is a complete gait cycle, from the initial contact of one foot to the subsequent initial contact of the same foot
  • Stride length measures the distance covered during one stride
  • Stride frequency or cadence is the number of strides taken per unit of time
• Step is the distance covered from the initial contact of one foot to the initial contact of the opposite foot
• Kinematics involves the study of motion without considering the forces causing the motion (joint angles, velocities, and accelerations)
• Kinetics is the study of forces acting on the body during motion (ground reaction forces, joint moments, and powers)

Biomechanics of Walking and Running

• Walking and running are distinct gaits characterized by different biomechanical patterns and energy expenditure
• During walking, there is always at least one foot in contact with the ground, and the center of mass (COM) reaches its highest point at midstance
• Running involves a flight phase where both feet are off the ground, and the COM reaches its lowest point at midstance
• Ground reaction forces (GRF) differ between walking and running
  • In walking, there is a double peak in the vertical GRF, representing the weight acceptance and push-off phases
  • Running exhibits a single peak in the vertical GRF, indicating the absorption of impact forces during the stance phase
• Joint angles, moments, and powers vary between walking and running, reflecting the different demands placed on the musculoskeletal system

Phases of the Gait Cycle

• The gait cycle consists of two main phases: stance phase and swing phase
• Stance phase is the period when the foot is in contact with the ground, making up approximately 60% of the gait cycle in walking
  • Stance phase is further divided into initial contact, loading response, midstance, terminal stance, and pre-swing
• Swing phase is the period when the foot is not in contact with the ground, making up approximately 40% of the gait cycle in walking
  • Swing phase is further divided into initial swing, mid-swing, and terminal swing
• Double support occurs when both feet are in contact with the ground simultaneously (initial contact and pre-swing)
• Single support occurs when only one foot is in contact with the ground (midstance and terminal stance)
• The timing and duration of these phases differ between walking and running gaits

Neural Control of Locomotion

• Central pattern generators (CPGs) in the spinal cord produce the basic rhythmic patterns for locomotion
• Supraspinal centers, such as the motor cortex, cerebellum, and brainstem, modulate and refine the output of the CPGs
• Sensory feedback from proprioceptors (muscle spindles and Golgi tendon organs) and cutaneous receptors provide information about the position and movement of the limbs
• Reflexes, such as the stretch reflex and the crossed extensor reflex, contribute to the regulation of muscle activity during locomotion
• Descending pathways, including the corticospinal tract and the reticulospinal tract, transmit commands from the brain to the spinal cord
• The coordination of muscle activity during gait involves the precise timing of agonist, antagonist, and synergist muscles

Factors Affecting Gait

• Age-related changes in gait include reduced stride length, decreased walking speed, and increased double support time
• Neurological conditions (Parkinson's disease, stroke) can lead to gait disturbances such as shuffling, freezing of gait, and asymmetry
• Musculoskeletal disorders (arthritis, fractures) can cause pain, stiffness, and altered joint mechanics, affecting gait patterns
• Environmental factors, such as uneven surfaces or obstacles, require adaptations in gait to maintain balance and stability
• Footwear and orthotics can influence gait by altering the interaction between the foot and the ground
• Cognitive factors, such as attention and executive function, play a role in gait control, particularly in challenging environments

Gait Analysis Techniques

• Observational gait analysis involves the visual assessment of gait patterns by trained clinicians
• Instrumented gait analysis uses technology to quantify gait parameters
  • Motion capture systems (optical or inertial) track the movement of markers placed on the body to determine joint angles and segment positions
  • Force plates measure ground reaction forces and moments during stance phase
  • Electromyography (EMG) records the electrical activity of muscles during gait
• Spatiotemporal parameters, such as stride length, cadence, and walking speed, can be measured using gait mats or wearable sensors
• Pressure mapping systems provide information about the distribution of pressure under the foot during gait
• Three-dimensional (3D) gait analysis combines kinematic, kinetic, and EMG data to provide a comprehensive assessment of gait

Pathological Gait Patterns

• Antalgic gait is characterized by a shortened stance phase on the affected limb to minimize pain (hip or knee osteoarthritis)
• Trendelenburg gait involves a drop of the pelvis on the swing side due to weakness of the hip abductors (gluteus medius)
• Steppage gait is marked by excessive hip and knee flexion during swing to compensate for foot drop (peroneal nerve palsy)
• Scissoring gait is characterized by a crossing of the legs during swing due to adductor spasticity (cerebral palsy)
• Parkinsonian gait features short, shuffling steps, reduced arm swing, and difficulty initiating movement (freezing of gait)
• Ataxic gait is characterized by a wide base of support, irregular step length, and difficulty with coordination (cerebellar disorders)

Practical Applications and Exercises

• Gait training exercises can be used to improve gait patterns and reduce the risk of falls in various populations
  • Treadmill training with or without body weight support can improve gait speed, endurance, and symmetry in individuals with neurological conditions
  • Overground gait training using visual or auditory cues can help regulate step length and cadence
• Strengthening exercises targeting key muscle groups (hip abductors, ankle dorsiflexors) can improve gait mechanics and stability
• Balance and proprioceptive training can enhance postural control and reduce the risk of falls during gait
• Functional electrical stimulation (FES) can be used to assist with muscle activation and improve gait patterns in individuals with paralysis or weakness
• Assistive devices, such as canes, walkers, or orthoses, can provide support and stability for individuals with gait impairments
• Gait analysis can inform the design and evaluation of interventions aimed at improving gait function and quality of life