Chapter 1 part 2- Muscular Control of Movement

motor units

the motor neuron and ALL the fibers it innervates

type 1 muscle fibers

slow twitch muscle making up about 50%

-contract slowly, mostly endurance

type 11a muscle fibers

fast twitch oxidative making up about 25%

more endurance (maintain force production)

type 11x muscle fibers

fast twitch glycolytic making up about 25%

anerobic- fatigue the quickest

motor neuron

determines the type of myosin ATPase that is produced

muscle force

the force generated by individual fibers is directly related to SIZE of fibers.

if a muscle fiber is the same size, it will generate the same force

power

involves both force and velocity

ForceXDistance/Time

motor units activation

more motor units will be activated the stronger the signal is.

more force will be produced the more motor units are activated.

rate coding

rate at which the motor units are fired.

more motor units fired, get to type 2 fibers quicker.

strengthen through resistance training

orderly recruitment and size principle

Recruit minimum number of motor units needed

Smallest (type I) motor units recruited first

Midsized (type IIa) motor units recruited next

Largest (type IIx) motor units recruited last

Recruited in same order each time

length-tension relationship

muscle is at optimal position when slightly stretched, producing the most force.

if too stretched or too short= little or no force development

optimal angle

angle with the highest torque production

concentric force

slower contraction speed = greater forces

isometric force

greater forces than concentric movements

eccentric forces

higher contraction speed= greater forces

speed-force relationship

- Concentric: max. force development decreases at higher speeds

- Eccentric: max. force development increases at higher speeds