Chapter 2 Flashcards
What is the origin of the muscle?
The proximal attachment, or the less mobile segment
What is the insertion of the muscle?
The distal attachment, the more mobile segment.
What do antagonist muscles do?
Aid in joint stabilization by providing a braking force at the end of motions.
What do synergist muscles do?
Aid indirectly with a movement, stabilize body movement when a muscle crosses two joints.
Describe a first class lever?
Muscle and resistance force act on opposite sides of the lever. Seesaw.
Describe a second class lever?
Muscle force and resistance force act on the same side of the lever, and the muscle has a longer moment arm and thus a greater mechanical advantage.
Describe a third class lever?
Muscle force and resistance force act on the same side of the lever, and the resistance force has a longer moment arm and thus a greater mechanical advantage.
What is a mechanical advantage?
When the applied force moment arm to resistive force moment arm is greater than 1.0. Allows muscle force to be less than resistive force.
What is a moment arm?
Perpendicular force from the line of action of the force to the fulcrum.
What is torque?
Degree of rotation about a fulcrum due to a force. T=force x moment arm.
What is the benefit of long moment arms? Short moment arms?
Long are good for generating high forces with low effort (mechanical advantage) but short are good for generating high velocities and are good for power but have a mechanical disadvantage.
Define strength
The ability to exert force
Define power
Explosive strength, change in velocity per unit time. Power = work/unit time
How can you fully assess strength?
Ability to exert force at various velocities. Use isometrics and different loads to assess sport specific abilities.
What is work?
work = force x displacement
What is negative power?
Eccentrics. When force is exerted in the opposite direction of the movement of a weight. The weight is working on the muscle.
What is angular displacement?
The angle about which an object rotates?
What is angular velocity?
The rotational speed of an object in radians per second.
What is the difference between work and torque?
Torque’s distance component refers to the length of the moment arm which is perpendicular to force, whereas the distance component of work is the distance moved along the line of action of the force.
What is rotational work?
torque x angular displacement.
What is recruitment?
Which and how many motor units are firing
What is rate coding?
The rate at which motor units are fired
When is force “greater”?
a) More motor units are involved with contraction
b) Motor units have a greater cross sectional area
c) The rate of firing is faster
What is the primary cause of early strength gains?
Neural adaptation
What occurs in muscles with great angles of pennation?
Greater force production due to increased # of fibers in parallel
What occurs in muscles with lesser angles of pennation?
Greater velocities, due to increased # of fibers in series
At what length can muscles generate the greatest force and why?
Resting length, due to overlap of actin and myosin.
Does torque very throughout ROM?
Yes, due to the alterations in moment arm length.
What is the relationship between the force capability of a muscle and the velocity of contraction?
Decreased force as contraction increases.
What type of muscle contraction can generate the most force?
Eccentric
What is the strength to mass ratio?
Ability to accelerate one’s body. You want a high ratio.
What is the classic formula?
Weight lifted divided by the body weight to the two-thirds power.
What are benefits of free weights?
- Whole body training
- Simulate real life actions
- More muscle groups involved
What are the benefits of machines?
Safety, ease of use, flexibility of design (can weight motions you can’t weight with free weights).
What is bracket training?
Trains acceleration. Use of low weight and then high weights to resist a motion.
What type of contractions do fluid resisted motions generate?
Alternating concentric, no eccentric. Higher velocity=higher resistance.
What is the relationship between stretch and resistance with elastic materials?
Greater stretch = greater resistance. More resistance at the end range of motions where there is the greatest stretch.
Would you recommend elastic bands for jumping resistance?
No the resistance is lower where muscle force can be greatest and vice versa.
Pros and cons of valsalva maneuver?
Pros: increased rigidity of torso. Cons increased compression of heart, impedes blood return possibly.
Should weight belts be used all of the time?
No, only during heavy sets that strain the low back. May decondition abdominal musculature.
