Biomechanics of Resistance Exercise Flashcards
Proximal attachment
Muscle origin; point closest to the center of the body
Distal attachment
Muscle insertion; point farthest from the center of the body
Agonist
Prime mover; muscle most directly involved in producing a movement
Antagonist
A muscle that slows or stops a movement; may also assist in joint stabilization
Synergist
Muscles that assist indirectly in a movement; may also help to stabilize the bone
Advantage of a long lever
Smaller required muscle force
Disadvantage of a long lever
Reduced movement speed
Sagittal Plane
Divides body left to right; bicep curls
Frontal Plane
Divides body front to back; lateral shoulder raise
Transverse Plane
Divides body into upper and lower sections; internal and external rotation of the shoulder, hip, torso, etc
Newton’s 2nd Law: Force =
Mass x acceleration
Work Equation
Work = Force x Displacement (distance object travels)
Power Equation
Power = Work/time
What muscle action is indicated by negative (-) work or power
Eccentric muscle action; the weight being lifted is applying more force to the muscle than the muscle is applying to the weight
Equation for rotational work around a joint
Rotational work = torque x angular displacement
Biomechanical factors that affect strength
Neural control, muscle cross-sectional area, muscle fiber arrangement, muscle length, joint angle, muscle contraction velocity, joint angular velocity, and body size
In what position does a muscle have the greatest force-generating potential?
Resting position; this is where the maximal number of crossbridge sites between actin and myosin are available
What happens to the force capability of a muscle as the velocity of muscle contraction increases?
Force capability decreases
Is strength-to-mass ratio usually higher in smaller or larger athletes?
Smaller athletes; increases in body size exceed increases in muscle cross sectional area (strength)
When a weight is horizontally closer to a joint, it exerts more or less resistive torque?
Less torque
When a weight is horizontally farther from a joint, it exerts more or less resistive torque?
More torque; bicep curl is hardest when elbow is at 90 and weight is in a straight horizontal line from elbow joint
Inertial Force (Inertia) =
mass x acceleration
Based on the principles of acceleration, is resistive force greater at the beginning of the movement or at the end range of motion?
Greater at the beginning range of motion; smaller at the end range of motion
Bracketing Technique
Technique in which athlete performs the sport movement with both lower than normal and greater normal resistance
How does the amount of muscular force required for a friction-based exercise change throughout the movement?
More force is required to initiate movement between 2 surfaces in contact than to maintain movement (the coefficient of static friction is always greater than the coefficient of sliding friction)
Does friction resistance change as speed increases?
No (but power output does)
When using fluid-resisted machines, what muscle actions do the agonist and antagonist muscles perform?
Both act concentrically (agonist acts concentrically to move the weight; antagonist acts concentrically to return the weight to its original position)
85-90% of back injuries occur at which two spots in the vertebral column?
Between L4 and L5 and between L5 and S1
Resistance training exercises involving the back should be performed with the back in which position to reduce injury?
A moderately arched position (lordotic) which is the natural neutral position of the spine.
Kyphotic back position
Rounded back
Recommendations for wearing a weight belt during lifts
- A weight belt is not needed for exercises that do not directly affect the low back
- Refrain from wearing a belt during lighter sets (to help develop necessary abdominal musculature) but may wear one for near-maximal and maximal sets
- Belts are not needed if athlete takes the time to properly progress and build up abdominal/back muscle strength
What are the 3 components of a lever?
- Fulcrum (the pivot point)
- Moment arm of the muscle force. This equals the distance from the muscle insertion point to the fulcrum
- Moment arm of the resistive force (ex. dumbbell). This equals the distance from the position of the weight to the fulcrum.
Mechanical advantage (or disadvantage) is determined by what?
The ratio of the moment arm of the resistive force to the moment arm of the muscle force
Does a mechanical ratio of greater than 1.0 indicate mechanical advantage or disadvantage?
Mechanical advantage
Does a mechanical ratio of less than 1.0 (ex. 1/2, 1/3, etc) indicate mechanical advantage or disadvantage?
Mechanical disadvantage
Type of lever in which the muscle force and and resistive force act on opposite sides of the fulcrum
First class lever
Example of first class lever
The forearm in elbow extension (tricep extension)
Type of lever in which the muscle force and resistive force act on the same side of the fulcrum, with the muscle force having a longer moment arm than the resistive force (and thus a mechanical advantage)
Second class lever
Example of second class lever
The foot in a heel raise
Type of lever in which the muscle force and resistive force act on the same side of the fulcrum with the muscle force having a shorter moment arm than the resistive force (mechanical disadvantage)
Third class lever
Example of a third class lever
The forearm in elbow flexion (bicep curl)
How does the patella increase the mechanical advantage of the quadriceps muscle?
By increasing the distance of the quad tendon’s insertion from the knee’s axis of rotation (fulcrum)
True or False: The mechanical advantage or the ratio of the moment arm of the resistive force to the moment arm of the muscle force changes throughout the movement
True; as the angle of movement changes so does the relative mechanical advantage
