Exam 2 Flashcards
describe longitudinal muscles
muscles with parallel or longitudinally arranged fibers
- some may not extend the full length of the muscle
- biceps muscle
describe pennated fibers
muscles with fibers oriented at an angle relative to the force generating axis
- vastus lateralis muscle
rationale for pennation
more fibers can be packed into a given area of muscle
Using similar numbers discussed in class, notate the the two diagrams to illustrate the difference between force output for longitudinal vs. pennated muscles.
- each rectangular prism = 1 muscle fiber (each muscle fiber has width of 1 muscle fiber = 1 cm)
- longitudinal: width = 6 fibers long = 6 cm
–> cross sectional area = 6 cm x 1 cm = 6 sq. cm - pennate muscle: cross sectional area made up of 2 sides that are each split between 3 different slices
–> cross sectional area = 2 (slice 1 + slice 2 + slice 3) = 16 sq cm - pennate muscle fibers: we can only calculate force of production in direction of force exertion –> only force going in same direction as muscle can be used to determine total force production of muscle (must use trig identity to find proportion of force that each muscle fiber is actually exerting for pennate muscle fibers)
describe how the the training portion of the curve demonstrates improvements in each of the 2 variables
- training improves the maximum force output at lower velocities and the ability to generate force at higher velocities, which shifts the entire curve to the right
- increasing the level of training will allow a trained individual to have greater power output at lower velocities/slower speeds and be able to generate more force at higher velocities/faster speeds than untrained individuals
list 2 different types of sports activities that these changes in the force velocity relationship reflect
- powerlifting improves maximum force at lower velocities
–> training focuses on maximum force output while doing slow and controlled movements, which in turn increases the ability to generate more force at slower speeds, allowing athlete to lift heavier with more control and improve strength - sprinting improves force generation at higher velocities
–> requires high velocity & explosiveness where athlete needs to generate force quickly at faster speeds
–> training increases ability to produce force at higher velocities, which improves power output during fast, dynamic movements
–> more trained –> more force at higher velocities –> improved performance in explosiveness –> shift curve to right
what must be true in terms of int/ext torque in order for motion to take place
- internal torque > external torque
- int force x int moment arm > ext force x ext moment arm
does a shorter or longer moment arm require more effort
shorter (more force needed to produce the same amount of torque)
how does pennation relate to force output
pennation = larger muscle cross sectional area = greater muscle size = more muscle fibers = increased strength/force output
explain internal torque
torque generated within the body
- in a human: torque produced by muscles around a joint during movement
- ex: leg muscles generate internal torque at the knee and hip to lift body
explain external torque
torque generated outside the body, often from external forces acting on body
- ex: when sitting, body is experiencing external force of gravity (body weight) & torque generated by gravity acting on your center of mass. seat surface creates external force that provides resistance to movement
why is a stool easier to rise from than a chair
- barstool: hips and knees higher than when in chair = moment arm (distance from center of mass to point where force is applied) is shorter = external torque is reduced (gravity acting on body) = less internal torque needed = less effort needed
- chair: hips & knees lower = center of mass farther from point of support = longer moment arm = gravity trying to pull body back down = more external torque acting on body = more internal torque needed to overcome resistance & stand up = harder
Describe in words, the anatomical measurements of the External moment arm when performing a “Push-up.”
- ext MA: distance from point of rotation to line of action of ext force
–> horizontal distance between the axis of rotation (elbow joint) and the line of action of the external force (gravity acting on the center of mass of body)
–> body lowered = elbows bent & COM farther from elbow joint = ext MA is longer = harder
–> pushed up = elbows extended & COM closer to elbow joint = ext MA is shorter = easier
Describe in words, the anatomical measurements of the Internal moment arm when performing a “Push-up.”
- int MA: distance between point of rotation & point where muscle force is applied
–> distance between axis of rotation (elbow joint) and the point where muscles generate force to perform movement (triceps, pect major, delts)
–> shorter when elbows are bent & body is closer to floor and longer when elbows are extended & body is higher off ground
–> shorter = more force necessary for same amount of torque = harder
–> longer = less force for same amount of force because force is spread over greater distance = easier
discuss the reason for the direction of the bulging of the IV disk being on the same side of spinal flexion (spine bending forward)
(points toward notches)
- the “other theory”: fibers on the expanded side tighten and push the nucleus pulposus to the concaved, compressed side
describe why labeling the spinal rotatores is now not accurate. Based on their composition, what are they more likely to accomplish?
- The moment arm they work from is very short, which limits the amount of twisting and bending torque
- There is no response from isometric contractions, but there is a major response when twisting in the opposite direction. This means that a response to position change rather than torque generation.
- it is more likely to accomplish the role of length transducer or vertebral sensor at each thoracic and lumbar motion segment
discuss the reason for the direction of the bulging of the IV disk being on the opposite side
balloon theory
- nucleus pulposus behaves like air inside of a balloon
- when force is applied to disc = pressure inside nucleus increases = nucleus shifts toward opposite side of applied pressure, where there is less resistance from surrounding annulus fibrosus
use the illustration to describe the forces acting on the different parts of the femoral head. also explain the arrows on the neck of the femur
- joint reaction force on the femur (J)
- bending moment (M)
- arrows pointing away: tensile forces
- arrows pointing in: compressive forces
explain text neck
- as flexion increases, the weight of the head moves progressively anteriorly
- as center of gravity moves forward, the ext torque increases
- extensor muscles provide forces for internal torque
why is this quote inaccurate (as the neck bends forwards & downwards, the weigh on the cervical spine begins to increase
- weight of cervical spine does not increase
- external MA becomes greater as neck bends forward = increase in ext torque (ext. torque = ext. MA * weight of head)
why are the postures assumed when using cel phones now a focus of concern
major concern bc it places a great load on neck as you look down to use phone
- as you increase degrees of flexion –> neck extensor muscles have to input a max of 60 lbs of force in order to maintain that posture
explain the flexion/relaxation phenomenon
- describes the relaxation of spinal muscles at full flexion of the torso, specifically the erector spinae
- support for the spine comes exclusively from the posterior spinal ligaments, which reduces the need for continued muscle contraction
explain asymmetrical frontal planar loading
List the prime movers for hip adduction, and contralateral lateral tilt of the pelvis
adductor magnus, adductor longus, adductor brevis
