BPK 143 Chapter Notes -Motor Unit, Osteoporosis, Myocyte

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Published on 13 Oct 2011
Simon Fraser University
Biomedical Physio & Kines
BPK 143
KIN 143 UNIT 5
Study Questions
1. Describe the four basic principles that should be adhered to if a person wishes to
obtain optimal benefits from a weight-training program.
1. Overload Principle
2. Principle of Progressive Resistance (2 for 2 rule)
3. Principle of Arrangement of Exercises (Larger muscles first)
4. Principle of Specificity
2. Compare advantages and disadvantages of isometric and isotonic strength
1. Isometric:
1. advantages:
1. For injury recovery
2. Strengthening muscle at a certain point of the ROM
2. disadvantages:
1. Does not improve movement that helps with sports
2. Strength gain only limited to that point in the ROM
3. Can increase blood pressure and cause extra work for heart
4. Does not make you powerful
2. Isotonic:
1. Advantages:
1. Will increase power
2. Natural movements we use everyday
3. Will improve athleticism
4. Improve ability to balance free weights
2. Disadvantages:
1. Does not exercise evenly throughout the ROM
2. Easier once the weight is accelerated
3. Less safe
3. Why is the average man stronger than the average woman, even when this
strength is expressed as a ratio of weight lifted to body weight?
1. Men have higher levels of testosterone so they put on more muscle mass
when they weight train. Testosterone also gives men a greater percentage
of muscle mass than women.
4. Distinguish between muscular strength and muscular endurance.
1. Strength:
1. How much force can be exerted in one instance?
2. Endurance:
1. How long can you continue exerting a given force?
5. Describe the mechanisms that a muscle uses to vary the force of a muscle
contraction from slight to maximal.
1. Muscles use motor units to exert force. One motor unit has a nerve that
controls a given number of muscle fibers. Firing more motor units will
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Document Summary

Isotonic: advantages, will increase power, natural movements we use everyday, will improve athleticism. One motor unit has a nerve that controls a given number of muscle fibers. Firing more motor units will result in more force exerted. Firing all motor units in a muscle is exerting maximal force. Isokinetic strength makes sure the muscle is fully exercised throughout the entire range of motion so the muscle gets stronger at every position in it"s range of motion. However, his muscle cross-sectional area has barely increased. Give a physiological explanation for his strength increase: neurologically the muscle is learning to fire more muscle fibers so the. 15% increase is strength is due to neurological learning of the muscle rather than muscle growth: compare the muscular strength of males versus females. Why is the average male stronger than the average female: male bodies contain more muscle mass while females contain more fat. Explain: type ii fast twitch muscle fibres.

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