Muscular Strength

Question 1

muscular strength

Answer 1

– Greatest amount of force that a muscle or muscle group can produce in a single maximal effort. (units: Kg)

Question 2

muscular endurance

Answer 2

– Ability of a muscle group to perform repeated contractions against a light load for an extended period of time. E.g. Push ups

Question 3

muscular power

Answer 3

– Ability to produce force quickly. (units: Watts, Kg m min-1) Eg. Vertical jump

Question 4

isotonic (dynamic) contraction

concentric contraction

eccentric contraction

Answer 4

– Iso (same) tonic (tone / force / weight) tension is the same throughout the range of motion.

– Muscle shortens with varying tension as it lifts a constant load.

– Muscle lengthens while developing force as the external resistance (weight) exceeds the muscle force, usually used in resisting gravity.

Question 5

isometric contraction

Answer 5

– Iso (same) metric (length) static contraction.

– Tension is developed but there is no change in the angle of the joint or the length of the muscle.

Question 6

isokinetic contraction

Answer 6

– Iso (same) kinetic (velocity) the muscle is shortened at a constant velocity determined by computer instrumentation which allows a person to exert maximal force throughout the full range of motion.

Question 7

5 Purpose of Strength Assessment

Answer 7

1. Assess muscular fitness
2. Identify specific areas of weakness
3. Monitor progress in a rehabilitation program
4. Measure effectiveness of a resistance training program
5. Motivation for training

Question 8

Strength Assessment Techniques [1/3]

a. One Repetition Maximum (1 RM)
b. Variable Repetition Maximum

Answer 8

a. Maximum amount of weight lifted once.

b. Estimation of one repetition maximum from repetitions to failure.

Question 9

Strength Assessment Techniques [2/3]

Dynamometer Techniques

Answer 9

– Strength testing dynamometer; usually consists of a spring of some type which is deformed a certain amount when a specific force is applied to it. (e.g. hand grip dynamometer, Jackson Strength Evaluation System)

Question 10

Strength Assessment Techniques [3/3]

Computer-Assisted, Isokinetic Methods

Answer 10

– Equipment such as Biodex, and Kin-Com.
– Test strength in isometric, concentric, and eccentric modes
– Can be programmed at any initial and final force, angle, velocity, or number of repetitions.
– Measure peak torque using a force transducer and joint angle using an electrogoniometer.
– Extensive manipulations can be performed on collected data using computer software.
– Accurate and reliable, but expensive.
– Used for research and elite athlete assessment.

Question 11

7 Strength Assessment Considerations (In addition to validity, reliability, etc.,)

Answer 11

1. Standardized instructions prior to testing.
2. Uniform duration and intensity in warm-up.
3. Consistent angle of measurement on the limb or test device among subjects.
4. Consider individual differences in body size and proportion when evaluating strength scores.
5. Test and training mode specificity are important for optimal expression of true strength gains.
6. Safety is an important consideration.
7. Test administrators should be well trained and have a thorough understanding of all testing procedures and protocols.

Question 12

Effect of Various Factors on Strength [1/5]

Muscle Cross Sectional Area

Answer 12

– Positive relationship between muscle CSA and strength.

– Muscles increase in strength by increasing their size and by enhancing the recruitment and firing rates of their motor units.

Question 13

Effect of Various Factors on Strength [2/5]

Body Size

Answer 13

– Positive correlation between body size or mass and absolute strength.

– Negative correlation between body mass and the strength/mass ratio.

– The strength to mass ratio directly reflects an athlete’s ability to accelerate his or her body.

– In comparing performances, the most widely used formula is to divide the weight lifted by body weight to the 2/3 power.

– Large athletes dominate sport events which require a high level of absolute strength (e.g., throwing events in track and field)
– Smaller athletes dominate sport events which require a high strength/body mass ratio (e.g., gymnastics).

Question 14

Effect of Various Factors on Strength [3/5]

Muscle Fiber Composition

Answer 14

– For a given size of muscle, there is a positive correlation between percentage of fast twitch fibers and strength.

Question 15

Effect of Various Factors on Strength [4/5]

Mechanical Factors

Answer 15

– Force exerted by a muscle is affected by:

a) the initial length of the muscle fibers
b) the angle of pull of the muscle on the bony skeleton
c) the speed of shortening

Question 16

Effect of Various Factors on Strength [5/5]

Muscle Strength and Sex

Answer 16

– After age 16, female is about 2/3 as strong as male when measuring absolute strength.
– Boys are only slightly stronger than girls prior to puberty.

Question 17

hypertrophy

Answer 17

– An increase in size of a cell such as a muscle fiber

– Muscle fiber hypertrophy accounts for most, of the increase in muscle cross-sectional area due to an overload training program.

Question 18

hyperplasia

Answer 18

– An increase in number of cells such as muscle fibers.

– Muscle fiber hyperplasia occurs in animals, but there is presently no direct evidence that it occurs in humans.