Ch 2: Biomechanics Flashcards
Synergist
Muscle that indirectly assists the agonist muscle and is required when the agonist muscle crosses 2 joints
1st class lever
Muscle force and restive force act on opposite sides of fulcrum
See-saw
Tricep pushdown
2nd class lever
Muscle force and resistive force act on the same side where the muscle force acts through a longer movement arm causing muscle force to be less than resistive force
Wheelbarrow
Calf raise
3rd class lever
Muscle force and resistive force act on the same side where the resistive force acting through a longer movement arm
Biceps curl
Tendon insertions and mechanical advantages
High insertions: Increase weight lifted due to increase in movement arm length but more contraction needed throughout a full ROM
Acceleration
Change in velocity / time
Work
Force x displacement
Power
work/time
Biomechanical factors of strength
- Neural Control
- Muscle CSA
- Arrangement of muscle fibers
- Length
- Joint angle
- Muscle contraction velocity
- Joint angular velocity
- Strength-to-mass ratio
- body size
Sources of resistance
- Gravity
- Inertia
- Friction
- Fluid resistance
- elasticity
What makes the back so vunerable to injury?
Compressive forces
Shoulder joint
Most ROM in the body, least stable
The classic formula
Load lifted divided by body weight to 2/3 power
Pennate muscle
Fibers align obliquely with the tendon and allow for more force production due to a greater amount of sarcomeres in parallel
Concentric muscle action vs. Isometric muscle action vs. Eccentric
Concentric: Muscle shortening
Eccentric: Muscle lengthening, produces most force
Isometric: no change in muscle length
