Muscle Performance

1. Muscle Performance Properties of Muscle Contraction

2. Muscle Twitch • Muscle Twitch - 1 simple muscle contraction

3. Phases of a Muscle Twitch • Latent period: time between release of neurotransmitter (muscle stimulus) and contraction of the muscle [~1milisecond = .001 second]

4. Phases of a Muscle Twitch 2) Contraction Period: shortening of spaces between muscle filaments, resulting in contraction of the muscle fiber [~ .04 seconds]

5. Phases of a Muscle Twitch 3) Relaxation period: neurotransmitter is broken down and the muscle fiber lengthens [~ .05 seconds]

6. Phases of a Muscle Twitch 4) Recovery period: waste products are metabolized (broken down); oxygen is required for this process [~60 seconds]

7. Vocabulary • Threshold stimulus - the weakest stimulus from a nerve cell that will excite the muscle fiber enough to initiate contraction • Subthreshold - a stimulus below the level required to excite a muscle

8. Vocabulary • All-or-None Law - a single muscle fiber will not partially contract, it requires a threshold stimulus and will completely contract {like a light switch = on or off}

9. Vocabulary • Summation - results when a series of subthreshold stimuli are applied rapidly to a muscle • Muscle tone - the state of normal contraction present in normal, healthy muscle tissue

10. Vocabulary • Tetanus (tetanic contraction) - sustained tension that results from elimination of the relaxation period due to rapid stimuli

11. Types of Skeletal Muscle Fibers (cells) • White, Fast Twitch Fibers: -use anaerobic respiration -fatigue rapidly -contain lots of glycogen stores -will hypertrophy (get bigger) with high-intensity, short duration exercise -sprints, tennis, weight lifting

12. Types of Skeletal Muscle Fibers (cells) • Red, Slow Twitch Fibers: -uses aerobic respiration -resistant to fatigue -surrounded by many blood vessels and contain myoglobin, an oxygen-binding protein = small stores of oxygen -low intensity, endurance exercises will develop this type of muscle fiber -distance swimming, cross-country skiing, marathons

13. Changes that occur in a muscle during exercise • High intensity: increase in muscle size due to increase in diameter of muscle fibers and increase in strength due to more myosin and actin filaments • Low intensity: more efficient delivery of oxygen and carbohydrates to muscles = improved performance

14. Changes that occur in a muscle during exercise • During exercise, not all fibers of the same muscle contract at the same time, if exercise is moderate, only slow-twitch fibers will be used. If exercise requires strong contraction, white fibers will be added • In some muscles, one type of fiber predominates but most muscles have both fiber types in proportions that vary from muscle to muscle.

15. Changes that occur in a muscle during exercise • Diet influences the rate at which a person can replenish his/her glycogen stores. After exhaustive exercise, a person on a high carbohydrate diet can replenish their glycogen stores in two days but a person on a high fat, high protein diet may take more than five days to replenish their glycogen stores.