Week 6 - Balance, Agility, and Aqua Therapy

Question 1

Center of mass (COM)

Answer 1

Is a point that corresponds to the center of the total body mass and is the point at which the body is in perfect equilibrium. It is determined by finding the weighted average of the COM of each body segment.

Question 2

Center of gravity (COG)

Answer 2

Refers to the vertical projection of the COM to the ground. In the anatomical position, the COG of most adult humans is located slightly anterior to the second sacral vertebra or approximately 55% of a person’s height

Question 3

Momentum

Answer 3

Is the product of mass times velocity. Linear momentum relates to the velocity of the body along a straight path, for example, in the sagittal or transverse planes.

Question 4

Angular momentum

Answer 4

relates to the rotational velocity of the body

Question 5

Base of support (BOS

Answer 5

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. A wide stance, such as is seen with many elderly individuals, increases stability, whereas a narrow BOS, such as tandem stance or walking, reduces it. As long as a person maintains the COG within the limits of the BOS, referred to as the limits of stability, he or she does not fall.

Question 6

Limits of stability

Answer 6

refers to the sway boundaries in which an individual can maintain equilibrium without changing his or her BOS. These boundaries are constantly changing depending on the task, the individual’s biomechanics, and aspects of the environment.

Question 7

Static balance

Answer 7

control to maintain a stable antigravity position while at rest, such as when standing and sitting

Question 8

Dynamic balance

Answer 8

control to stabilize the body when the support surface is moving or when the body is moving on a stable surface, such as sit-to-stand transfers or walking

Question 9

Ground reaction force

Answer 9

the reaction from the contact between our bodies and the ground due to gravity (action forces)

Question 10

Center of pressure (COP)

Answer 10

the location of the vertical projection of the ground reaction force. It is equal and opposite to the weighted average of all the downward forces acting on the area in contact with the ground. If one foot is on the ground, the net COP lies within that foot. When both feet are on the ground, the net COP lies somewhere between the two feet, depending on how much weight is taken by each foot. When both feet are in contact, the COP under each foot can be measured separately.

Question 11

Balance

Answer 11

a complex motor control task involving the detection and integration of sensory information to assess the position and motion of the body in space and the execution of appropriate musculoskeletal responses to control body position within the context of the environment and task. Thus, balance control requires the interaction of the nervous and musculoskeletal systems and contextual effects

Question 12

Ankle balance strategy

Answer 12

movements at the ankle act to restore a person’s COM to a stable position

Question 13

Weight-shift balance strategy

Answer 13

movement strategy utilized to control mediolateral perturbations involves shifting the body weight laterally from one leg to the other

Question 14

Suspension balance strategy

Answer 14

is observed during balance tasks when a person quickly lowers his or her body COM by flexing the knees, causing associated flexion of the ankles and hips.

Question 15

Hip balance strategy

Answer 15

uses rapid hip flexion or extension to move the COM within the BOS

Question 16

Stepping balance strategy

Answer 16

a forward or backward step is used to enlarge the BOS and regain balance control

Question 17

Feedforward (open loop motor control)

Answer 17

is a type of balance control that is utilized for movements that occur too fast to rely on sensory feedback (e.g., reactive responses) or for anticipatory aspects of postural control.

Question 18

Anticipatory control

Answer 18

is a type of balance control that involves activation of postural muscles in advance of performing skilled movements, such as activation of posterior leg and back extensor muscles prior to a person pulling on a handle when standing or planning how to navigate to avoid obstacles in the environment.

Question 19

Closed loop control

Answer 19

is a type of balance control that is utilized for precision movements that require sensory feedback (e.g., maintaining balance while sitting on a ball or standing on a balance beam).

Question 20

Aquatic exercise

Answer 20

the use of water (in multidepth immersion pools or tanks) that facilitates the application of established therapeutic interventions, including stretching, strengthening, joint mobilization, balance and gait training, and endurance training

Question 21

Buoyancy

Answer 21

the upward force that works opposite to gravity

Question 22

Archimedes’ principle

Answer 22

states that an immersed body experiences upward thrust equal to the volume of liquid displaced

Question 23

Hydrostatic pressure

Answer 23

the pressure exerted by the water on immersed objects

Question 24

Pascal’s law

Answer 24

states that the pressure exerted by fluid on an immersed object is equal on all surfaces of the object. As the density of water and depth of immersion increase, so does hydrostatic pressure

Question 25

Viscosity

Answer 25

friction occurring between molecules of liquid resulting in resistance to flow

Question 26

Surface tension

Answer 26

surface of a fluid acts as a membrane under tension. Surface tension is measured as force per unit length.

Question 27

Hydromechanics

Answer 27

comprise the physical properties and characteristics of fluid in motion

Question 28

Laminar flow

Answer 28

hydrodynamic movement in which all molecules move parallel to each other, typically slow movement

Question 29

Turbulent flow

Answer 29

hydrodynamic movement in which molecules do not move parallel to each other, typically faster movements.

Question 30

Drag

Answer 30

the cumulative effects of turbulence and fluid viscosity acting on an object in motion

Question 31

Specific heat

Answer 31

the amount of heat (calories) required to raise the temperature of 1 gram of a substance by 1°C

Question 32

Center of buoyancy

Answer 32

rather than center of gravity, is the reference point of an immersed object on which buoyant (vertical) forces of fluid predictably act