factors that affect muscle tension
What are the factors that affect muscle tension ?
motor units recruitment,
Length-tension relationship,
Muscle Force - Velocity Relationship,
Angle of pull and.
Active and passive insufficiency.
How does motor unit recruitment affect muscle tension ?
• Difference between lifting a minimal, vs. maximal resistance is the number of muscle fibers recruited.
• The number of muscle fibers recruited may be increased by
• activating those motor units, containing a greater number of muscle fibers.
• activating more motor units
• increasing the frequency of motor unit activation.
• the more motor unit we recruit or engage will determine the amount of tension we will generate
What is • Tetanus ?
results if the stimuli are provided at a frequency high enough, that no relaxation can occur between contractions- therfore Increasing the frequency will result in a sustain muscle contraction.
What is the lenght tension relanship?
• sarcomere contains thick and thin filament actin(thin) and myosin (thick) proteins.
• Tension is develop when the cross bridges on the actin and myosin hook up and energy is released and the cross bridge will pull the actin over the myosin and cause contractions.
When can a muscle attain the greatest tension?
• Muscle can generate greatest tension at
• its resting length
• when a muscle is shorten their isn't enough tension
• when the sarcomer is shorten their isn't enough tension
• when the sarcomere is lengthen the sarcomer will generate more tension
• in order to bulk up you have to stretch
When does a muscle decrease its ability to attain tension ?
- Greatest amount of tension can be developed when a muscle is stretched between 100% to 130% of its resting length
- Stretch beyond 100% to 130% of resting length significantly decreases the amount of force muscle can exert
• A proportional decrease in ability to develop tension occurs as a muscle is shortened
• When shortened to around 50% to 60% of resting length ability to develop contractile tension is essentially reduced to zero
What is Muscle Force - Velocity Relationship?
When muscle is contracting (concentrically or eccentrically) the rate of length change is significantly related to the amount of force potential
When contracting concentrically against a light resistance muscle is able to contract at a high velocity
When contracting concentrically against a light resistance muscle is able to contract at a high velocity
Slight increases in load results in relatively low velocity of lengthening
As load increases further the velocity of lengthening will increase as well
Eventually, load may increase to point where muscle can no longer resist, resulting in uncontrollable lengthening or dropping of load
What is Angle of pull?
• Angle between the line of pull of the muscle & the bone on which it inserts. (angle toward the joint)
What is - Rotary component?
component of muscular force that acts perpendicular to long axis of bone. (lever)
When the line of muscular force is at 90 degrees to bone on which it attaches, all of the muscular force is rotary force, (100% of force is contributing to movement)
All of force is being used to rotate the lever about its axis
The closer the angle of pull to 90 degrees, the greater the rotary component
What are the secondary componets of angle of pull?
- Secondary force component is the horizontal, or nonrotary component and is either a stabilizing component or a dislocating component, depending on whether the angle of pull is less than or greater than 90 degrees.
• If angle is less than 90 degrees, the force is a stabilizing force because its pull directs the bone toward the joint axis.
• If angle is greater than 90 degrees, the force is dislocating due to its pull directing the bone away from the joint axis.
What is Active and passive insufficiency ?
• As muscle shortens its ability to exert force diminishes
- Active insufficiency is reached when the muscle becomes shortened to the point that it can not generate or maintain active tension
- Passively insufficiency is reached when the opposing muscle becomes stretched to the point where it can no longer lengthen & allow movement
• Easily observed in either biarticular or multiarticular muscles when full range of motion is attempted in all joints crossed by the muscle
One joint muscle don't maintain tension(powerful)
2 joint muscle maintain tension they are efficient