Lecture 11 - Assessment of muscle strength & power

Question 1

How does training velocity effect improvements in strength and power

Answer 1

• Training a low velocity improves strength and power a low speeds only.
• Higher velocity only improved higher speed strength and power.

Question 2

How should the testing of strength be a specific as possible?

Answer 2

• Testing conditions should imitate the movement/activity & training conditions.

Question 3

What is isokinetic strength testing and how is it done ?.

Answer 3

• Dynamic movement testing done at set speeds but the load and resistance changes, e.g. cybex machine.

Question 4

What are some Mechanical and Performance Variables of vertical jump test?

Answer 4

• Impulse
• Take-off velocity
• Power (average/peak relative/absolute) Jump height (CoM displacement)
• Rate of force development
• Speed-Strength (SJ)
• Reactive Strength Index (RSI)

Question 5

What methods can be used to gain Isotonic strength of an athlete, how is this done, and what do you gain from it?

Answer 5

• Free weight or resistance machine testing 1RM, 3RM + 5RM.
• Done with constant load put the speed of the contractions changes
• Determination of critical mechanical factors affecting performance (e.g. CM acceleration, rate of force development)

Question 6

What are two types of jump that can be used to measure speed and power, and what do they assess?

Answer 6

• Either slow SSC jumps (>250ms) such as CMJ & squat jumps.
• Or fast SSC jumps (<250ms) such as Drop jumps
• All types measure leg extensor power

Question 7

How do measure isometric strength?

Answer 7

• Perform tests with fixed load and fixed speed (as weight does not move).

Question 8

To what speed can angular velocities reach during sprinting

Answer 8

• 1150 degrees / second during early and late swing phase.

Question 9

What are the pros and cons of isometric strength testing.

Answer 9

• Pros - Easily performed, isolates muscle group, accurate.

- Cons - Static movements, only measures strength at one position, difficult to elicit a true MVC.

Question 10

What are the application of lab based kinetics analysis ?

Answer 10

• Profiling, discriminative analysis, pre-post training adaptations.

Question 11

What are the strengths and limitations of isokinetic testing?

Answer 11

• Pros - Good for dynamic muscle testing and the ability to isolate the muscle, ensuring maximal resistance through ROM.
• Cons - Is not a real movement and cannot match the velocities attained during dynamic activities.

Question 12

What is the purpose of carrying out strength assessments?

Answer 12

• Ability to distinguish between athletes at different levels
• Indicator of ‘good’ athletic performance
• Correlation with athletic performance
• Sensitivity to training adaptations
• Availability of normative data for comparison
• Injury prevention

Question 13

What are the pros and cons of isotonic strength testing?

Answer 13

• Pros - easily performed, allows quantification of data
• Cons - Little scientific analysis, not as accurate as is only relates to the amount of torque produces by the weakest joint position.

Question 14

What variables are measured during isokinetics tests?

Answer 14

• Peak Torque: The maximal value of all torque values measured during an isokinetic test.
• Mean Torque: Average value from several repetitions
• Peak Torque to Weight Ratio: Peak moment compared to body weight
• Angle of Peak Torque
• Time to Peak Torque
• Total Work: Total amount of work produced during the Isokinetic exercise.
• Power: Relates to the average time rate of work.
• Reciprocal Muscle Group Ratio: Indicator of joint balance (agonists-antagonists).