Midterm 2 Flashcards
developmental changes
- changes are based on optimizing principles of motion and stability
- changes can be seen across a variety of motor skills
- changes often produce more force, velocity, or accuracy
- occur according to biomechanics principles
biomechanics
the study of forces acting on and generated within the body and the effects of these forces on the tissues, fluids, or materials used for diagnosis, treatment or research purposes
- motion and stability are two principles within the larger field of biomechanics, known as the physics of movement
force
strength or energy exerted, as an attribute of physical action or movement, measured in newtons
mass
the mass of a body refers to the amount of substance that it is made up of and is measure in weight
velocity
the rate of change of position of an object in a particular direction
acceleration
any time velocity changes, if you are not changing speed, you are not accelerating
inertia
- the idea that an object will continue its current motion (whether moving or stationary) until some force causes its speed or direction to change
- resistance to change in speed or to get moving
- opposing change in direction or speed
momentum
- the product of mass and velocity
- mass in motion
- how much motion something or someone has
we must exert force to
- move objects
- move ourselves
more inertia/momentum
- it is harder to move
- more force application is required
to move an object farther or faster
- increase the force delivered to the object
- increase distance over which force is applied
newton’s first law
- an object at rest stays at rest, and an object in motion stays in motion until acted upon by a force
- any object that is moving will continue moving unless an external force is applied to stop it from moving
- this law is about inertia
- once a ball is struck in tennis, its forward trajectory would continue indefinitely if the forces of gravity, friction from the air resistance or striking the ground and the force of the opposing player’s racket did not stop it
newton’s second law
- Force = mass x acceleration
- object’s acceleration is related to force applied and inversely related to mass
- acceleration is the rate of change of the velocity of an object with respect to time
- mass is how much matter the object contains
- tennis serve: the mass of the ball remains constant, therefore the more force you apply to the constant mass of the ball, the greater the acceleration of that serve will be until it reaches top speed
newton’s third law
- to every action, there is an equal and opposite reaction
- when you push on something, it pushes back on you
force and time
- to make an object move, increase force application for a given time
- to make an object stop, increase time over which a given force is applied
balance
- a person’s ability to control their equilibrium in reaction to gravity only
- equilibrium is a state of rest of the body either at a stationary or moving position
- equilibrium is a state of no acceleration and can be static or dynamic
stability
- your body’s ability to return to a desired position or trajectory following a disturbance to equilibrium
- if acceleration is occurring, we’re talking about stability
- as our body needs to respond to acceleration and return to a desired position or trajectory
increasing stability
- stability = ability to resist movement
- increase base of support
- lower center of gravity
increasing balance
- balance = ability to maintain equilibrium
- increase stability
- improve strength, coordination, and proprioception
proprioception
ability to sense movement, action and location
stability-mobility trade-off
- new movers adopt stability strategies that maximize stability and balance but hinder quick movement
- with development and improvement in ability to maintain upright posture during movement, movers shift to mobility strategies so they can move faster
what is locomotion?
- the ability to move from one place to another
- often focus on early acquisition of locomotor skills
- locomotion is a lifelong movement activity
- changes occur in walking, running, galloping, and other motor skills as individual, environmental and task constraints change
senior runners
- at the 2018 USA Track ad Field Masters Championships, there were two world records set in the 60m dash
- in the women’s 100+ age group, Julia “Hurricane” Hawkins, at 102, set a new world record with a time of 24.79 seconds
- Orville Rogers set a world record in the mens 100+ 60m race with a time of 19.13 seconds, Rogers held seven world records in the 95-99 bracket
locomotion
- moving from place to place
- moving on one, two, or four limbs: crawling, walking, running, hopping, skipping, galloping, using other modes
constraints
- discourage or limit certain movements
- encourage or permit other movements
- “shape” movements, channel away from some movements while toward others
individual constraints
- unique physical, mental characteristics
- structural: related to the body’s structure: height, muscle mass
- functional: related to behavioural function: attention, motivation, fear
environmental constraints
- properties of the environment, external
- global, not task specific
- physical: gravity, surfaces
- sociocultural: gender roles, cultural norms
task constraints
- specific task requirements or goals, external to the body and not related to the individual
- related specifically to tasks or skills: goal of task, rules guiding task performance, equipment
rate controller/limiter
- an individual constraint or lack of development of a system that holds back the development of a motor skill
- a toddle may be strong enough to hold herself up, but its a lack of balance that limits the progression from standing to walking
- a 5 yr old shooting a basketball, lack of muscular strength to get it to the 10ft hoop, strength is then the system that is the rate limiter/controller
study of locomotion
- falls within many fields, from medicine to psychology
- across the lifespan, individuals use various methods of locomotion
- the type of locomotions they use depends on interacting constraints
locomotion across lifespan
- childhood years: height, weight, and lengths change dramatically and act as rate controllers
- during much of the lifespan, other types of constraints, such as motivation or even perceived gender association of a skill may encourage or discourage behaviour
- as one approaches old age, structural constraints such as physical characteristics may return as important rate controllers, however functional constraints such as fear of falling or loss of balance capability, may acts just as strongly to discourage locomotion
- environmental constraints such as weather changes (eg. ice and snow) also impact older adults
early locomotion of crawling
the following progression of skills leads to creeping and crawling:
1. crawling with the chest and stomach on floor, commando crawling
2. low creeping with the stomach off the floor but the legs working together symmetrically
3. rocking back and forth in the high creep position
4. crawling with the legs and arms working alternately
walking
- walking is the first form of upright, bipedal locomotion
- walking is defined by the following:
- 50% phasing between the legs, individuals alternate their legs so that the left leg is halfway through its motion as the right leg begins its own
- period of double support followed by period of single support
early walking
- stability and balance are maximized over mobility
- arms are in high guard
- feet are out-toed and spread wide apart
- independent steps are taken
- rate controllers are strength (to support body on one leg) and balance
rate limiters in early walking
- infants have the ability to move their legs in an alternating pattern from birth onward, yet they cannot walk for at least 7 months
- critical levels of development required to overcome these rate-controlling factors:
- legs must be able to move alternately, and must have enough strength to support themselves on a single limb -> muscle strength in the trunk and extensor muscles to allow them to maintain an upright posture on a small base of support
- must also balance on one leg while transferring weight to other foot
proficient walking (1)
- stability is traded for mobility
- stride length increases
- base of support is reduced
- pelvis is rotated
- opposition (arms to legs) occurs
- double knee-lock is adopted: knee extends at heel strike, flexes slightly as the body weight moves forward over the supporting leg, and then extends once more at foot push-off, because the knee extends twice in one step cycle we call this double knee-lock
proficient walking (2)
- by age 4, most children have the essential ingredients of an advanced walk
- the length of time for which one foot supports the body weight while the other swings forward increases, especially from 1.0 year to 2.5 years
- stride length increases throughout mid-adolescence, partly because of fuller ROM at the hips, knees, and ankles and partly because of the increase in leg length resulting from growth
- velocity of walk also increases, especially between 1.0-3.5 years of age
- rhythm and coordination of a child’s walk improve observably until age 5 or so, beyond this age improvements are subtle
developmental changes in walking in older adulthood
- stability is maximized
- out-toeing increases
- stride length decreases
- pelvic rotation decreases
- speed decreases
- objects are used as balance aids
rate controllers in later walking
- structural constraints may result from osteoarthritis in the joints or from a decline in muscle mass, a disease sate must progress to a critical level before it will discourage all walking
- more often, older adults modify their gait to accommodate pain or changes in balance
- functional constraints, such as balance and fear, can also affect walking patterns
- often, two types of individual constraints will interact, and their sum will act as a rate controller
- a decrease in walking leads to a decrease in muscle mass and flexibility, which in turn affects walking patterns
running
- occurs 6-7 months after walking starts
- for a gait to be considered a run it must include a flight phase
- an infant’s earliest attempts to run are actually fast walks
early running
- stability over mobility: return of old “behaviours”
- arms in high guard, limited ROM, short stride length, little rotation
- infants running for the first time may exhibit some of the characteristics of an early walk, even though the infant no longer uses these in their walk
rate limiters for early running
- running requires a flight phase
- strength: to propel themselves into the air, toddlers must have sufficient strength in each leg to lift themselves off the ground
- balance: once in the air, infants must catch themselves on the other leg and then balance on that leg while shifting their weight forward