MSK Flashcards
What language should be incorporated into every discussion about physical testing?
Every discussion about physical testing should incorporate the following: Safety, Validity, Reliability, Precision, Practicality, and Professionalism
What are the primary reasons for conducting physical tests?
The primary reasons to test are to:
* Identify strengths and weaknesses, and appropriate training loads.
* Monitor and evaluate progress, plateaus, and decline.
* Enhance the education process through prescription and feedback.
* Serve as a health status indicator
Define strength and muscular endurance
- Strength is ideally defined as the maximal weight you can lift once but not twice. It can also be considered the maximum force.
- Muscular endurance is the ability to perform more repetitions at the same load before the onset of fatigue, or to maintain a muscle contraction or continue repetitive muscle contractions for a prolonged period of time to a defined endpoint
What are the basic types of muscle contractions?
The basic types of muscle contractions are dynamic, isometric, and isokinetic. More specifically:
* Isometric: force generation without movement.
* Concentric: force generation when muscle shortens.
* Eccentric: force generation when muscle lengthens
What is isokinetic dynamometry?
Isokinetic dynamometry is a type of test that keeps velocity static to isolate changes in strength across a range of motion and controls the velocity of movement. It can be set to “0” velocity for isometric contractions. Examples of machines include Cybex, KinCom, and Biodex
Explain the relationship between muscle architecture and strength.
- Cross-sectional area (CSA) provides an indication of how many muscle fibers directly contribute to force production. Increased muscle mass generally means more muscle fibers. Larger fibers adapt more to strength training.
- Muscle length: longer, slender muscles are more conducive for faster contractions, while shorter, thicker muscles are more conducive for forceful contractions. Volume is length x CSA.
- Pennation: a greater degree of pennation directly impacts sarcomere fiber number per cross-section of muscle, leading to more force applied for a given anatomical cross-sectional area. Pennation sacrifices shortening velocity for increased force per volume of muscle.
What is Post-activation Potentiation (PAP)?
Post-activation potentiation (PAP) refers to short-term increases in maximal force following near-maximal contractions. However, measuring PAP at the muscle level is often not done, and confounding factors like muscle temperature are often not accounted for in studies. Performance improvements after a warm-up may simply be due to the warm-up itself, not necessarily PAP
How does joint position affect strength testing?
Joint position matters during strength testing, as the joint angle at each position will influence the force produced. Good overlap across different joint angles is beneficial for overall strength
Explain the role of neural drive in strength.
Neural drive influences strength through:
* Recruitment: the activation of motor units. Endurance training recruits a portion of muscle fibers, while maximal voluntary contraction (MVC) attempts to recruit as many motor units as possible.
* Rate coding: the frequency of action potentials sent by motor neurons. Untrained individuals adapt more quickly through neurological factors
Describe the relationship between contraction type and maximal force output.
While strength can be measured at any velocity, maximal (functional) force output will occur at a low velocity or during an isometric contraction. However, eccentric contractions will generally generate the most force
What is a motor unit and a motor pool?
- A motor unit is defined as a single alpha motor neuron (MN) and all the muscle fibers it innervates. Type II (fast fatigable) motor units have a high ratio of muscle fibers to a single nerve and are involved in strength, while Type I (slow oxidative) motor units have a low ratio and are involved in endurance.
- A motor pool is defined as all the alpha-motor neurons that innervate one muscle
What is Maximum Voluntary Contraction (MVC)?
Maximum Voluntary Contraction (MVC) is an attempt to voluntarily recruit as many muscle motor units as possible for the movement pattern to generate as much force as possible.
Why must extreme caution be undertaken when testing maximum strength?
extreme caution must be undertaken when testing maximum strength due to the potential for injury. Stability must precede force expression.
What are the three main categories of strength measurements based on contraction type?
strength measurements can be:
1. DYNAMIC (concentric and eccentric movement), e.g., 1 RM and mRM.
2. ISOMETRIC (static), e.g., Hand Dynamometry.
3. ISOKINETIC, e.g., Cybex, Kin-Com
Describe the 1 Repetition Maximum (1RM) test.
A 1 Rep Max (1RM) test measures the maximum amount of weight that can be voluntarily lifted once while the muscle shortens (concentric contraction). To truly measure concentric strength, a pause should be included, and the starting position standardized. It is often considered the gold standard for strength
Outline the N.S.C.A. 1RM Protocol.
The N.S.C.A. 1RM Protocol includes:
* Set 1: 8-10 reps of light load (~40-60% of estimated 1RM).
* Set 2: 3-5 reps of higher load (~70% of estimated 1RM).
* Set 3: 2-3 reps of higher load (~80-90% of estimated 1RM).
* Set 4: Increase load for a 1 rep max. Instruct the client to attempt a 2nd rep, and complete additional sets until failure on the 2nd attempt occurs. Continue doing 1 rep sets and adding weight until the lift cannot be completed.
Allow a minimum of 3 minutes rest between sets
What are some important protocol concerns for 1RM testing?
Protocol concerns for 1RM testing include:
* Accuracy of the weight of bars, collars, and plates.
* Standardized warm-up (general to specific).
* Avoiding “bouncing” or rebound effect.
* Controlled number of lead-up sets and reps to avoid fatigue but provide progressive overload.
* Adequate rest between sets (~3 min).
* Controlled range of motion, joint angle, posture, grip, timing, and time of day
What is the reliability and validity of 1RM testing? What are some cautions?
- Reliability is very good (e.g., U. of A. test-retest: r = .94 to .97; ICC = .87).
- Validity is very good, provided the amount of weight lifted once is relevant to the population.
- Cautions: Not recommended for certain groups, and it can be difficult to achieve a “true” 1 RM in untrained populations
Describe Multiple Repetition Maximum (mRM) testing.
Multiple Rep Max (mRM) testing is an alternative to 1RM testing where the maximum number of repetitions at a given load is determined. Reliability and validity are similar to 1RM testing. An example protocol includes sets at different percentages of estimated 1RM.
How can mRM results be used to predict 1RM?
Based on a reasonably linear relationship, 1RM can be predicted using formulas based on the number of repetitions completed at a given weight. For example, if 6 reps are completed with X lbs, and 6 reps correspond to approximately 85% of 1RM, then Estimated 1RM = X lb / (85/100). However, RM tables are not perfect, and the relationship can become curvilinear beyond 10 reps, especially for the bench press. Lower body exercises like the leg press may produce higher rep counts and have more variability compared to the upper body. Predictions are more accurate for single-joint exercises and heavier loads (>75% 1-RM).
Describe isometric strength assessment and some of the devices used.
Isometric strength assessment measures the maximum amount of muscle force with “no” movement. Devices include cable tensiometers, isokinetic dynamometers, and handgrip dynamometers. It is considered by some to be the gold standard technique for strength measurement
What are some protocol concerns for isometric strength assessment?
Protocol concerns for isometric strength assessment include:
* Body positioning and isolation of the movement pattern being tested are critical.
* Joint angle is critical; an isometric strength curve may need to be determined.
* Avoid “jerking” by gradually increasing tension development.
* Hold maximal contraction for 3 seconds, and repeat 3 times
Describe the handgrip dynamometer and its significance.
The handgrip dynamometer measures isometric grip strength. It has a moderate correlation with upper body strength in a large population and is used by CPT. It can be used for early screening of populations at higher risk for physical disability related to low muscle strength. A cutoff score of 21.0 kg for grip strength in older adults indicates an 8 times higher risk of developing muscular strength disabilities. It is a good indicator of high and low levels of health status. Test-retest reliability is high. Always take the highest number for strength tests
Describe isokinetic dynamometers and some of their considerations.
Isokinetic dynamometers keep velocity static to isolate changes in strength across a range of motion and control the velocity of movement (up to 400º/s, can be set to 0 for isometric). Concentric force will decrease with an increase in velocity, while eccentric contractions generate the most force. Max power generally occurs at ⅓ max velocity and ⅓ max force. They allow isolated single-joint testing, but multiple joint testing is difficult. Considerations include being expensive, requiring strict adherence to manufacturer control settings and calibration, and the need for familiarization due to a learning factor. Reliability is high
