Balance & Stability Flashcards
(32 cards)
What is balance and postural stability?
Balance and postural stability describe the dynamic process by which the body’s position is maintained in equilibrium. Balance is greatest when the body’s center of mass (COM) is maintained over its base of support (BOS).
What is the Centre of Mass (COM)?
The COM is the point that corresponds to the center of total body mass where the body is in perfect equilibrium. It is determined by finding the weighted average of the COM of each body segment.
What is the Centre of Gravity (COG)?
The COG is the vertical projection of the center of mass to the ground. In the anatomical position, the COG in most adults is slightly anterior to the second sacral vertebra or approximately 55% of a person’s height.
What is the Base of Support (BOS)?
The BOS is the perimeter of the contact area between the body and its support surface. Foot placement alters the BOS and changes a person’s postural stability.
What are Limits of Stability?
Limits of stability refer to the sway boundaries in which an individual can maintain equilibrium without changing their BOS. These boundaries change based on the task, biomechanics, and environmental aspects.
What is balance control?
Balance control is a motor control task that involves detecting and integrating sensory information to assess body position/motion in space and using musculoskeletal responses to control body position based on the task and environment.
What three systems interact to provide balance control?
- Nervous System
- Musculoskeletal System
- Sensory Systems – visual, vestibular, and somatosensory
What role does the visual system play in balance?
It provides information about:
a) The position of the head relative to the environment
b) Orientation of the head to maintain level gaze
c) Direction and speed of head movements
What does the somatosensory system detect for balance?
It provides information about the position and motion of the body and body parts relative to each other and to the support surface through:
• Muscle proprioceptors (muscle spindles and Golgi tendon organs)
• Joint receptors (position, movement, and stress)
• Skin mechanoreceptors (vibrations, touch, deep pressure, stretch)
What does the vestibular system detect for balance?
It provides information about head position and movement relative to gravity and inertial forces:
• Angular acceleration and fast head movements
• Linear acceleration and head position (gravity, slow movements)
Can the vestibular system alone determine body position?
No. It cannot differentiate between a head nod (head moving on stable trunk) and a forward bend (head moving with trunk). It must work with other systems.
How is sensory input processed for postural control?
Sensory input is integrated and processed through the cerebellum, basal ganglia, and supplementary motor areas for adaptive and anticipatory responses.
What happens if one sensory system is injured?
The CNS receives inaccurate input, which slows processing time. The CNS must suppress the faulty input and rely on other systems for correct information.
What musculoskeletal components contribute to balance?
• Postural alignment
• Musculoskeletal flexibility (joint ROM)
• Joint integrity
• Muscle performance
• Sensation
What are the three movement strategies the CNS uses to regain balance after perturbation?
• Postural alignment
• Musculoskeletal flexibility
• Muscle performance and coordination
What is the function of foot position and weight distribution in balance?
Foot arches help distribute weight and support postural stability. There are three arches: Medial Longitudinal, Lateral Longitudinal, and Transverse.
What is the function of the Medial Longitudinal Arch (MLA)?
It is the largest arch and supports the body during weight-bearing and compressive forces.
Bones:
• Calcaneus
• Talus
• Navicular
• Medial Cuneiform
• 1st Metatarsal
Muscles:
• Abductor hallucis
• Tibialis anterior
• Tibialis posterior
• Flexor hallucis longus (supports calcaneus and talus, • • stretches arch like bowstring)
• Peroneus longus
What is the function of the Lateral Longitudinal Arch (LLA)?
It is the lowest arch and is responsible for transmitting weight.
Bones:
• Calcaneus
• Cuboid
• 5th Metatarsal
Muscles:
• Peroneus brevis
• Peroneus longus
• Intrinsic foot muscles
What is the role of the Transverse Arch?
It is a non-weight bearing arch that provides stiffness to the foot during the gait cycle.
Bones:
• Metatarsals
• Cuneiforms
• Cuboid
Muscles:
• Adductor hallucis
• Peroneus longus
• Tibialis posterior (from medial side)
• Interosseous muscles
What are contextual effects in balance control?
Contextual effects are factors that interact with sensory and motor systems in balance control, including:
• Type of environment (CLOSED = predictable, no distractions; OPEN = unpredictable, with distractions)
• Support surface (firm vs. slippery, stable vs. unstable, type of shoes)
• Amount of lighting
• Effects of gravity and inertial forces
• Task characteristics (well-learned vs. new, predictable vs. unpredictable, single vs. multiple tasks)
What is a CLOSED environment in balance training?
A closed environment is predictable and free of distractions.
What is an OPEN environment in balance training?
An open environment is unpredictable and has distractions.
How can the support surface affect balance?
Balance can be affected by whether the surface is firm or slippery, stable or unstable, and by the type of shoes worn.
What task characteristics influence balance?
Whether the task is well-learned or new, predictable or unpredictable, and single or multiple tasks.
