Gait and Gait Cycle Overview

Gait

• Gait is the study of human locomotion, including walking and running.
• Walking consists of a series of gait cycles, each cycle known as a stride.

Gait Cycle/Stride

• A single gait cycle or stride is the period when one foot contacts the ground until the same foot contacts the ground again.
• Each stride has two phases: stance phase and swing phase.
• Stance phase: the foot is in contact with the ground (approximately 60% of the gait cycle). Further divided into:
  • Heel strike to foot flat
  • Foot flat to mid-stance
  • Mid-stance to heel off
  • Heel off to toe off
• Swing phase: the foot is not in contact with the ground (approximately 40% of the gait cycle). Further divided into:
  • Initial swing
  • Mid-swing
  • Terminal swing
• Stride has two periods of double limb support (both feet on the ground)
  • Loading response (right) and toe off (left)
  • Loading response (left) and toe off (right)

Gait: Physiology

• Gait depends on the integrated function of bones, muscles, and the nervous system (Central and peripheral).
• The degree of integration determines the different gait patterns.
• Defects in any part of this system will lead to pathological gait.

Gait: Mechanical

• Gait is a form of bipedal locomotion achieved by rhythmic alternating actions between the lower extremities.
• One leg supports, restrains, and propels, while the other leg is in the swing phase to initiate the next step.
• Movements of the arms, legs, and trunk create the forward movement of the body.

Normal Walking Requirements

• Equilibrium: the ability to maintain balance and assume an upright posture.
• Locomotion: the ability to initiate and maintain rhythmic stepping.
• Musculoskeletal Integrity: normal bone, joint, and muscle function.
• Neurological control: must receive and send messages telling the body how and when to move (visual, vestibular, auditory, and sensorimotor input).

Nerve Lesions

• A neuron is the basic functional unit of the nervous system.
• In mature humans, if a neuron is destroyed, it is not replaced.
• Nerve injuries can be caused by cutting, crushing, pulling, or applying pressure.
• Nerve injuries are categorized by the extent of damage sustained.
• Seddon (1944) described 3 clinical types of nerve injury:
  • Neurapraxia (Class 1): a transient block; paralysis is incomplete; recovery is rapid and complete; no nerve degeneration. Pressure is a common cause.
  • Axonotmesis (Class 2): a nerve lesion with damaged axons but intact surrounding connective tissue; Wallerian degeneration occurs peripherally; functional recovery is more rapid than if the nerve trunk is completely severed. Crush injuries, traction, and compression are among the most frequent causes.
  • Neurotmesis (Class 3): complete section of the nerve trunk; typically caused by severe contusion, stretch, or laceration.
• Sunderland (1951) expanded the classification to 5 degrees, with some overlap with the Seddon classifications (first-degree = neurapraxia; second-degree = axonotmesis).

Types of Nerve Injuries (Sunderland Classification):

• First-degree: Similar to Seddon's neurapraxia; minimal damage, with rapid and good recovery
• Second-degree: Similar to Seddon's axonotmesis; axon damage with intact connective tissue; moderate recovery, but takes more time compared to first degree
• Third-degree: Lesion of endoneurium, with intact epineurium and perineurium; possible recovery with or without surgery
• Fourth-degree: Epineurium only remaining intact; surgical repair needed. Possible but often needing surgical intervention
• Fifth-degree: Complete transection of the nerve; complete loss of function, likely needing surgical intervention

Nerve Injury: Changes (general)

• Wallerian degeneration: distal changes in the injured axon
• Chromatolysis: changes in nerve cell body (nucleus shifted to the periphery, swelling)
• Regeneration considerations:
  • Peripheral nerves have good regenerative capacity due in part to the endoneurial tubes and Schwann cells.
  • CNS regeneration is less effective due to a lack of functional Schwann cell counterparts, and possible presence of growth inhibiting factors

Terminology

• Paralysis: complete loss of motor function.
• Paresis: incomplete loss of motor function.
• Anesthesia: loss of all sensation.
• Hyperesthesia: excessive sensory input.
• Hypoesthesia: diminished sensory input.
• Hyperalgia: excessive sensitivity to painful stimuli.
• Hypoalgesia: decreased sensitivity to painful stimuli.

Nerve Fiber Types

• A-alpha: largest fiber, fastest conduction, fine touch, position (balancing)
• A-beta: proprioception (balancing)
• A-delta: sharp pain, fast
• C fibers: slow pain

This quiz explores the fundamentals of human locomotion, focusing on gait cycles and strides. Learn about the phases of the gait cycle, including stance and swing phases, and their significance in walking and running.