biomechanics Test 1

• Goal of most resistance training?

  Increase size and strength of target muscle group AND increase performance of a particular skill
• increase in strength substantially through weight lifting DOES NOT mean increase in performance of skills
• the training exercise should be as similar to that skill as possible
• similarities to increase skill?

  same range of motion, sequence of joint movements, direction (concentric or eccentric), posture, velocity, acceleration patter, power AND same muscles
• kitai and sale (2004) showed that 6 weeks of isometric exercises at one joint angle achieved significant strength gains at that angle and 2 adjacent angles (+-5 degrees) but not at other ones WITH NO changes when electrically stimulated
• isokinetic machine manufacturers claim that strength gains were speed specific
• Caizzo did a study that indicated that when individuals train at a slow velocity, they experience a strength gain at that velocity and lower (red line) but very little gain when tested at high velocity.  Those who trained at a high velocity had a greater strength gain at high velocity (blue line) but not as much at the low velocity.
• isometric and low velocity lifting = significant strength gains at low velocity but not when high velocity
• training with lighter weights at faster speeds or an isokinetic dynamometer at high speed= greater strength gains at high velocity and perhaps even a greater Vmax of the muscles
• acceleration that achieves the greatest final velocity is different than the acceleration that minimizes movement time

  
• large increases in spontaneous power are required for modest increases in velocity
• if peak force must be exerted at a higher velocity then it requires a higher instantaneous power
• rapid increase in strength is attributed to neural factors such as:
• rapid increases in muscle strength is attributed to neural factors such as:

  1. increased firing rate of MU
  2. increased recruitment of MU
  3. increases synchronization of MU firing
• sum of 2 unilateral lifts is greater than the amount that can be lifted bilaterally
• what activities are unilaterall?

  running, shot put
• what activities are bilateral?

  volleyball spike (Jump)
• specificity principle recommends that a unilateral exercise is used to improve a unilateral skill
• resistance exercise has been shown to not only increase the size of muscle, but to increase central motor drive, elevate motor neuron excitability, and reduce presynaptic inhibition
• Isometric training has been shown to decrease the recruitment threshold and increase the firing rates of motor units within only a few training sessions
• differences in force-length or force-velocity OR differences in neural drive can explain the relationship between strength and speed