Lecture 4 - Lucas Flashcards
4 types of contraction
concentric, eccentric, isometric, isotonic
explain concentric contraction
muscle shortens while generating force (contracts)
ex: a bicep curl towards your body (upward phase)
force is greater than resistance
explain eccentric contraction
Muscle lengthens while generating force (contracts).
Example: a bicep curl away from your body (downward phase), extends elbow
muscle force is less than resistance in order to control the descend
explain isometric contraction
muslce contracts (tension) but doesnt change length bc theres no movement
ex: quad muscles during a wall sit, holding a weight, use to test maximum strength
muscle force = resistance
isotonic contraction
a muscle contraction where the muscle length changes while the force remains constant (ex: concentric shortens or eccentric lengthens)
ex: Using a machine that applies a constant load (force) in a lab while the muscle shortens or lengthens
whole muscle length tension relationship
length of a muscle and the amount of force it can produce at that length. It’s a measure of how much tension a muscle generates as it contracts or shortens.
difference between sacromere length relationship and whole muscle length tension
sacromere = Optimal force occurs at a specific sarcomere length where thick and thin filaments overlap perfectly (21. to 2.2)
whole muscle = involves (passive) elasticity (e.g., tendons, connective tissue) and interactions between different muscle fibers.
Force is not solely based on sarcomere overlap but also on the passive stretch from elastic components.
explain the force velocity relationship
High force = low velocities (more cross-bridges attached).
High velocity = low forces (cross-bridges cycle rapidly but fewer are attached at any moment).
as velocity increases, forces decrease
why is eccentric on the left and concentric on the right in the force-velocity curve
Scenario: Lowering a heavy box after holding it.
Key Points:
The velocity is negative because the muscle is lengthening while resisting the load.
Force is greatest because the muscle must control the descent of the heavy box.
Example: Lowering a barbell in a controlled manner during a bench press (eccentric contraction of chest muscles).
isometric: holding the box steadily without movement
concentric: Lifting the box above your head.
Key Points:
The velocity is positive because the muscle is shortening to lift the load.
Force decreases as velocity increases:
If the box is heavy, you lift it slowly (lower velocity, higher force).
If the box is light, you can lift it quickly (higher velocity, lower force).
Example: Lifting a barbell during a bicep curl (concentric contraction of biceps).
sacromeres in series vs in parallel
parallel: More sarcomeres in parallel mean more cross-bridges generating force simultaneously.
series: sEach sarcomere adds its shortening rate, increasing total velocity.
Contraction definition
Generation of tension via cross-bridge cycling; does not necessarily involve shortening. (can shorten, can lengthen or stay the same)
definition of shortening
Muscle actively reduces its length by sliding filaments, always involves contraction (concentric)
relaxation definition
No cross-bridge activity; the muscle is at resting length.
residual force enhancement
When a muscle is actively stretched to a specific length and held isometrically, the force remains higher than expected compared to the same isometric contraction without prior stretching.
reasons:
some myosin heads may become strongly attached to actin in a stretched configuration.
titin adds passive elasticity force
benefits of residual force enahncement
rFE allows muscles to generate higher forces with less metabolic cost during dynamic activities.
