Muscle Performance Properties of Muscle Contraction

Muscle Twitch Muscle Twitch - 1 simple muscle contraction

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

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

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

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

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

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}

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

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

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

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

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

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.

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.