L2 Movement mechanics and Contraction types

Actin is what kind of filaments

Actin is what kind of filaments

Thin

Myosin is what kind of filaments

Thick

Force output is related to what?

The number of cross bridges occurring at the same time.

Force output is related to

active and passive components

Explain active component

voluntary activation-the number of cross bridges occurring at the same time

Explain passive component

no voluntary activation

Looking at the force length at a single fiber where is tension maximal?

At intermediate lengths and decreases at shorter and longer lengths

Looking at the force length at a whole muscle where is tension maximal?

At longer length because of the contribution of active and passive components

Looking at the force length at the joint where is the tension maximal?

At intermediate lengths and decreases at shorter and longer lengths, however does not correspond to the whole muscle relations, rather mimics the single fiber force-length relation

Because cross bridges slide past each other, is their reattachment slower or faster. Is it a mechanical separation?

Faster, therefore is a mechanical separation and no need for ATP

Looking at force-velocity for the whole muscle when does force output decrease?

shortening contractions

Why does force velocity decrease during shortening contractions?

Because the binding sites are missed as the thick and thin filaments slide past each other at a fast speed.

Looking at the joint where does force velocity decrease?

During shortening contractions the force output decreases with velocity.

During lengthening contractions where is force output with velocity.

it is constant

Is the force output influenced by the design of the muscle?

Yes, each muscle is different

When a muscle is arranged in series what is the ROM

Greater ROM

When muscles are arranged in parallel what is the ROM

less ROM but greater force generation

When muscles are arranged in pennation angle what does this mean

Maximize number of fibers in a given volume and thus max force capacity.

Although muscles produce linear forces motions at joints are all…

rotary

What is the rotary torque

Product of the linear force and the moment arm or the mechanical advantage of the muscle about the joints center of rotation.

What is the Torque equation

Force (N) x Lever arm (m)

Why do we have a patella?

• It increases moment arm

• Increases angle of pull on tibia

Some muscles have short tendons, Why?

Shorter moment arm will result in better involvement through ROM

Some muscles have long tendons, Why?

Longer MA will result in greater muscle torque generation

Many muscles cross 2 joints instead of one. Why?

• Couple the movement of two joints, is better and more efficient for coordination

• The shortening velocity of a two-joint muscle is less than that of its one-joint synergist

• Redistribution of muscle torque, joint power, and mechanical energy throughout the limb

Explain concentric ROM

• Muscle torque is greater than the load

• Muscle shortens

• Load is lifted, think the way up of a bicep curl

Explain Eccentric ROM

• Muscle torque is less than load

• Muscle lengthens

• Load is lowered

Looking at an example recording of eccentric and concentric force output. What is the 2 y axis’s on the data chart

• Left: SD of Acceleration

• Right: AEMG

What happens to force output when we voluntarily shorten the muscle ?

Less Force

What happens to force output when we voluntarily lengthen the muscle?

Greater force