General Questions Flashcards
Define a concentric contraction
MTU shortens
Positive mechanical work is performed
Cross bridges are formed and myosin exerts a force on the actin filament creating movement towards teh centre of sarcomere (power stroke)
Cross bridges are broken and reform at a point further along the actin filament, sarcomere shortens
Define eccentric muscle activity
Muscle attachemmets move away from each other and MTU lengthens
Work occurs as force moves through a distance - muscle is active in order to resist an external force = negative mechanical work
Cross bridges are formed, myosin filament exert a force (power stroke) on actin filament creating movement, cross bridges break and reform at a different point making the sarcomere longer - direction of movement is reversed from concentric movement
MTU is active whilst lengthening in a controlled manner - eccentric contraction is used to decelerate movements
How is torque related to a concentric contraction
Intrinsic torque is greater than the extrinsic torque and so muscle attachments approach each other
As MTU shortens
How is torque related to an eccentric contraction
Extrinsic torque is greater than intrinsic intrinsic torque
Muscle attachments move away from each other as the MTU lengthens
What is torque
Tendency of a force to cause rotation around an axis / the effectiveness of a force in causing rotation
Torque = force X perpendicular distance from axis of movement
Intrinsic torque VS Extrinsic torque
E = I - isometric contraction
E > I - eccentric contraction
E < I - concentric contraction
What is eccentric loading
Exercise that focuses on the the eccentric phase of muscle contraction
(The weight is typically greater that what can be lifted concentrically - in an exercise athlete focuses on controlling the lowering phase of movement)
It increases muscle strength and size
More tension is produced during an Eccentric contraction (so you can lower a greater load than you can lift - eccentric loading is more effective as a strengthening exercise than other types of muscle activity)
Can lead to greater muscle growth and strength gains
^ lengthening a muscle to generate maximal muscle tendon = sports where the MTU is actively stretched eccentrically prior to explosive activity
The passive tension produced by MTU lengthening acts like a spring which recoils the MTU - generating increased force
Explain length tension relationship
What is the optimal length?
Relationship between the length at which an MTU is active and the amount of tension the MTU can generate
Explained though actin and myosin cross bridge formation
Short position = no more room for cross bridges to slide to generate tension
Lengthened position = reduced overlap of myosin and actin so less cross bridges formed and less tension generated
Optimal length at which it can generate maximum force is mid range but slightly elongated
What is origin-insertion reverse
Example
When a muscle moves it point of origin towards its point of insertion
The line of pull is changed and muscle moves through its range of motion in a way that puts the muscle on a stretch
Always in closed kinetic chain
Occurs when insertional attachment is more stable
Tib ant, when foot is stable on floor and push knees over foot
Push up, biceps,
What is active insufficiency
What range does it happen in
When does it affect 2 joint muscles
What part of MTU is affected
Inability of MTU to generate sufficient tension to respond to demands placed on it, because it has been placed in a inefficient position
Insufficient cross bridges formed to cope with demands and muscle therefore cannot generate sufficient tension
Happen in inner or outer range
Affects 2 joint muscles more commonly when they are required to do all there actions at all joints
The contractile elements of MTU is affected because it relates to generation of tension
What is passive insufficieny
What range does it oocur in and what part of an MTU does it affect
When does it occur In 2 joint muscles
Inability of MTU to lengthen adequately to allow full range of motion to occur.
Affects non-contractile elements and occurs when MTU is relaxed while being lengthened - can be due to another muscle activity or an external force
Happens in outer range muscle if both ends are elongated
What is the Clinical significance of active and passive insufficieny
In muscle testing and exercise prescription
Working muscles hard in actively or passive insufficient ranges may cause injury
What is active tension
What’s it influenced by
Tension generated by contractile elements of the MTU
Influenced by -
Num and frequency of motor units firing
Num of muscle fibres in the cross section
Type of muscle activity
Num of corss bridges formed in sarcomere
What is passive tension
Generated by non-contractile elements of the MTU
Tension develops when MTU is lengthened
What is a first class lever order
What are the functions in the body and give an example
What is the mechanical advantage
The fulcrum is positioned between the force and the load
For balance - generally isometric - equilibrium between force and effort
Change in direction - direction of effort force applied to one end of the lever may be reversed at other end
Sit to stand
F = Cx spine
E = extensors
L = wieght if head
What is a 2nd class lever
What are the functions in the body and give an example
What is the mechanical advantage
Load is in the middle
For strength increasing force, allows us to increase torque with little force - a small force applied at one end of lever and at a large distance from axis
Generally eccentric contractions
MA > 1
> effort is further away than load arm to fulcrum so less load is required to move more resistance
Heel raise
Fulcrum = 1st MTP
Load = gravity
Effort = muscle power from Gastroc
Bicep curl
Fulcrum = elbow
Load = gravity down
Effort = brachioradialis
