Kinetics

Question 1

Kinematics

Answer 1

Description of motion

Question 2

Kinetics

Answer 2

Causes motion
Ex: Force and Torque
Are important because it describes injury!

Question 3

Force

Answer 3

Vector

Push, pull, rub (friction) or blow (impact)

Causes a motion (acceleration) or a change in shape of an object

Question 4

Characteristics used to describe a Force

Answer 4

Magnitude

Direction

Point of Application

Question 5

What direction will this go? What happens with force?

Answer 5

Compression and rotation occurs because we strike the ground on the lateral side leads to pronation or eversion

Question 6

Force coupling associated with scapular motion

Answer 6

Muscle forces are internal forces that rotate the scapula
Force couple = more than one force to rotate scapula
Muscles = internal force
Gravity = external force

Question 7

Ground Reaction Force

Answer 7

All surfaces produce a reaction force

If you push against the ground the ground pushes back with equal and opposite direction.

GRF is commonly measured using a force platform

While walking, forces will be anterior posterior and vertical motions

Cutting will be three forces, Ant Post, Med Lat, Vertical

GRF are external forces

Question 8

Ground Reaction Forces during Walking Gait

Answer 8

Stance is 60%, Walking has no flight stage (Contact on ground load goes up, “load response”; peaks are typically about the same height; in the middle is called a trouf as a result of knee bent at midstance; Pushing off increases force; force decreases as the foot leaves the plate

Swing is 40% (No Force)

Deceleration creates a higher force

Flex knee reduce load on knee

We feel acceleration and deceleration (changes)

When accelerating force goes up.

Medial and Lateral is extremely variable

Breaking is negative and propulsion is positive typically

Question 9

Heel Strike Transient

Answer 9

Additional bump at the beginning og the heel strike (could mean no socks or shoe didn’t properly take the force)

Question 10

What is the force related to BW while walking?

Answer 10

1.5x

Question 11

What is the force related Bw while running?

Answer 11

2-4x

Question 12

Ground Reaction Forces in Heel Toe Running (Rearfoot Strike Running)

Answer 12

75% strike the ground with their heel

2-4x the body weight

Impact is lower than what the invididual actively puts into the ground

Question 13

How does injury relate to rearfoot strike running?

Answer 13

Too much force over many repitions during loading rate (first slope) is related to injury such as stress fractures and patellofemoral pain.

Forefoot runners have less of an initial slope and are therefore less at risk. Forefoot and rearfoot have the same amplitude at peak force.

Question 14

Vertical Ground Reaction Forces for Jumping and Landing

Answer 14

Time with no force is mean in the air. The longer in the air the higher the jump.

Steepness of landing curve is tough on bones, joints and ligaments.

Try to teach to touch with toes and bend knees on landing. Thus makes deloading peak less aka safer.

Question 15

Impulse

Answer 15

Impulse = Force * Time

Breaking impulse, vertical impulse, etc

Quantifies the magnitude of loading

Caused by a change in momentum when impacting the ground

Question 16

Anterior-Posterior Forces “Braking and Propulsion Impulses Speed Relation

Answer 16

Constant Speed: Breaking = Propulsive

Slowing down: Breaking > Propulsive

Speeding up: Breaking < Propulsive

Question 17

Joint Reaction Force (JRF)

Answer 17

Translate GRF to the joint

Doesn’t incorporate muscle necessarily

Requires force plate measurements and video analysis

Simple way to reduce force is going slower

Load transmission = off loading

Cushioned shoes dampen ground force

Long steps = more force

Question 18

Ground Forces and OA

Answer 18

Ground forces are different with people with OA. If we want to change force on a person we give them something to reduce it such as a cane or biking instead or walking.

Question 19

Ankle Forces and Shoes

Answer 19

Forces at a joint are not solely about muscles contracting but also cushion. Reaction force + muscle force = contact force. Contacr force is force between bony segments. Softer shoe puts less forces on it.

Question 20

Impulse Example: Helmet and no helmet, hit with a ball

Answer 20

Impulse is the same regardless of wearing a helmet or not when getting hit in the head. The magnitude will be of no helmet will be high with a small time which will be a high sharp peak. The magnitude with a helmet will be smaller and more averaged with a larger time.

Question 21

Injury Prevention

Answer 21

Decreased GRF

Therefore, decreases JRF
- Individuals with OA have altered forces due to no cartilage to dampen forces.

Can decrease GRF by:
- Leading with toes and bending knees to be able to slowly load forces
- Avoid repeated fast force changes as a steeper slope in loading is related to stress fractures and patellofemoral pain over a period of time.
- Wear cushioned shoes to reduce forces
- Take smaller steps
- Using biking, swimming or assistive devices to offload weight