KNES 289 Study Guide - Fall 2018, Comprehensive Midterm Notes - Torque, Tendon, Nervous System
12 Oct 2018
School
Department
Course
Professor
KNES 289
MIDTERM EXAM
STUDY GUIDE
Fall 2018
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
find more resources at oneclass.com
find more resources at oneclass.com
○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
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Subsystems that produce human movement: nervous and sensory system--muscles---skeletons. 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. Vertical direction has to average out to your body weight. Phase that you use muscles to swing legs forward. You extend your knees and arrest the motion of the knee. 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. Muscle generates force in a active way. Tendon--rubber band--it can be stretched and generate force and has to retract. Muscle and tendon: muscle and tendon unit. 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.
