Kinesiology lecture 3

what is strength by academy sports medicine

Strength refers to the muscle’s ability to generate force at a given velocity

what is strength neumann text

maximal force or power produced by a muscle or muscle group during a maximal voluntary contraction.

what are the factors of muscle force that impact strength

number of motor units activated (recruitment)

frequency of activation (rate coding)

types of cross-sectional area

muscle length during activation

muscle contraction velocity

how does moment arm impact strength

there needs to be a mechanical advantage

moment arm needs torque at joint axis

how is strength measured?

manual muscle testing

dynometer

functional testing

how does strength vary?

age, gender, speed of contraction, length of muscle, joint , angle of joint, action

How to gain more strength?

resistance = high, reps= low , load= increase

how to gain more endurance?

resistance= low, reps=high, duration = increase

what is the percentage decrease after 1 week of immobilaization?

3-6% strength loss per day

which fibers are afeected the most when immobilized?

slow-twitch fibers

are all fibers affected when immobilized?

yes

What position are muscles immobilized experiencing the most loss of strength?

shortened position

single joint

antigravity muscles

what types of exercises can reverse loss of strength changes in a patient?

resistive exercises

eccentric movements

moving with gravity

what are examples of single joint/ antigravity muscles?

soleus, vastii, multidus, spine muscles

what barries in O&P can restrict strength gain?

phantom pain, wounds, injuries

what is the equation for equilibrium?

f1xd1=f3xd3

Can a force vector be changed into vertical and horizontal components and if so what are they?

yes, x and y

what direction of a component relating to a joint or surface indicated a compression force?

force directed toward the joint

what direction of a component relating to a joint or surface indicated a tension force?

away from the joint

what direction of a component relating to a joint or surface indicated a shear force?

parallel to force or joint

is clockwise torque positive or negative

negative

is counterclockwise torque positive or negative

positive

Consider the Posterior Deltoid muscle’s location at the glenohumeral joint. 1. Why can the Posterior Deltoid create Adduction motion in the frontal plane?

the weight of the forearm acts with gravity to adduct

Consider the Posterior Deltoid muscle’s location at the glenohumeral joint.What motion does the Posterior Deltoid create in the sagittal plane?

extension

Consider the Posterior Deltoid muscle’s location at the glenohumeral joint.Why is the Posterior Deltoid able to create motion in the sagittal plane?

there is a moment arm at the joint axis allowiing to create toque to create motion

internal forces> external forces

how do patients move when they lack strength

compensate for other muscles

use assistive devices

change of center of mass

how might moment arm change with amputation of disease?

moment arms are shorter making it more difficult to generate torque

what does the length of a force vector determine

magnitude of force

what are the steps of making a free body diagram

1. Identify and draw the segment of interest

2. Add coordinate reference axis (+x, +y, + torque)

3. Identify and draw the joint axis of rotation

4. Identify and draw the external forces on the segment

5. Identify and draw the internal forces acting on segment

6. Draw internal torque on joint

what is the right hand rule used to find?

z axis

what is a ground reaction force

equal and opposite

upward from ground

what is muscle force?

directed from origin to insertion or insertion to origin depending on action

what is joint force reaction?

draw as parallel and perpendicular forces at joint surface