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KNES 289 Study Guide - Fall 2018, Comprehensive Midterm Notes - Torque, Tendon, Nervous System


Department
Kinesiology
Course Code
KNES 289
Professor
Time Kiemal
Study Guide
Midterm

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KNES 289
MIDTERM EXAM
STUDY GUIDE
Fall 2018

Only pages 1-3 are available for preview. Some parts have been intentionally blurred.

Only pages 1-3 are available for preview. Some parts have been intentionally blurred.

8/31/18
Subsystems that produce human movement: nervous and sensory
system--muscles---skeletons
All it is a closed loop
For running and walking there are two phases
Phase that foot is in contact with ground so the stance phase
Muscles are used to support body weight
Accurate body forward in late stance
Vertical direction has to average out to your body weight
Phase that you use muscles to swing legs forward. This is the swing phase
You extend your knees and arrest the motion of the knee
You aren't on the ground
Difference between running and walking you spend both feet on the ground
more when walking
In running the stance phase is less than half the duration of one stride
All these forces comes from muscle
Muscle tendon unit
Muscle generates force in a active way
Tendon--rubber band--it can be stretched and generate force and has to retract.
Cannot create net energy
Muscle and tendon: muscle and tendon unit
Tendon attaches to the bone
Kinematics is the description of movement
Any time you move those muscle tendons have to change length
One implication is that if you have fast movement you will have fast changes in
length
The muscle tendon unit does it produces force
It produces force by
We know that the nervous system has some control over muscle force but it
does not direct how much force to produce
Does not direct desired length either it is not that simple
There are two things that force depends on
The neural command of the nervous system
The muscle tendon length from the skeletal system
two inputs to the system and we have to know oth to know what force is
being produced
Muscle -tendon is a input-output system
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Needs to know the history of the neural command and the length up to the
present time that determines the force at the present time
Muscle tendon compliance
Means external force can change its length
That means you do not know the muscle tendon length because you do not
know the external force
This is a good thing because bend don't break
Robotic controllers are not compliant
Muscle approximation--static input and output system
Dependa on the present time of activation, length and velocity to get the
muscle force of the present time
Contraction: muscle is producing force
In order to sprint you have to move quickly and the muscle tendon units have
to change quickly
But if length changes quickly you can only produce weak force
So how do you produce strong force
The key is that force velocity relationship describes muscles but it does not
describe the muscle tendon unit
The reason we can sprint is because of tendons. The achilles tendon is very
long so it can stretch a lot
Achilles tendon has short moment arm
Distance from tendon to joint
Short for such a big muscle
Distance where the rotation is taking place is the moment arm
Force that leads the rotation
If you have a large moment arm, the muscle tendon unit changes a lot
If its small moment arm there is less muscle tendon unit length change
Sprinters have short moment arms
Proportion of fast twitch fibers
They generate force more quickly and they make more force so they are ideal
for sprinters
Your speed is a combination of stride length times frequency
You can go faster by taking longer strides
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