1. I. Muscle Metabolism A.Background ATP is the source of energy for muscle contraction. ATP is required to break down actin-myosin cross bridge. Muscles store a very limited amount of ATP (4-6 seconds worth at most). ATP must be regenerated if contraction is to continue beyond 4-6 seconds. ATP can be generated by one of three pathways….

2. I. Muscle Metabolism B. Aerobic Metabolism/Cellular Respiration 1. Description: Occurs in mitochondria, requires oxygen, and involves a complex sequence of chemical reactions. 2.Chemical Formula: Glucose + oxygen  carbon dioxide + water+ energy (36 ATP) 3.When this system is used: Prolonged endurance activities which maintain a constant heart rate. As long as there is enough oxygen available, a muscle will utilize aerobic metabolism. Posture, most daily movements, marathon runs, bike riding

3. I. Muscle Metabolism C. Anaerobic Metabolism/Glycolysis 1. Description: Vigorously contracted muscles compress blood vessels, impairing oxygen delivery. Occurs in the absence of oxygen. 2.Chemical Formula: Glucose  lactic acid +energy (2 ATP) 3.When this system is used: When large amounts of ATP are needed for periods of exercise about 30-40 seconds long. Tennis, soccer, 100 meter swim

4. I. Muscle Metabolism D. Anaerobic Metabolism/Creatine Pathway 1. Description: Utilizes creatine phosphate to regenerate ATP, after stored ATP is depleted. 2.Chemical Formula: Creatine phosphate + ADP  Creatine + ATP (1ATP) 3.When this system is used: At the beginning of exercise, before other pathways ‘ kick in ’. Creates enough energy for about 15 seconds of contraction. 100 meter dash, weightlifting

5. I. Muscle Metabolism E.Summary Creatine PathwayGlycolysis PathwayAerobic Pathway Requires Oxygenno yes Amount of ATP1 ATP2 ATP36 ATP Duration15 sec30-60 sechours By-productcreatinelactic acidCO 2, H 2 O Advantagesrapid energy easily mobilized quick energy does not require oxygen moreATP/glucose waste products are easy to excrete Disadvantagessmall amount of creatine available small amount of ATP lessATP/glucose lactic acid produces muscle fatigue slower limited by oxygen

6. II. Muscle Fatigue A.Definition: the state of physiological inability to contract B.Causes 1. Occurs when ATP production fails to keep up with ATP use. 2. Accumulation of lactic acid and ionic imbalances also contribute. decreases muscle pH causes burning sensation interferes with actin/myosin binding

7. A. Fast Twitch/Slow Twitch Muscle III. Muscle Fiber Types

8. A. Fast Twitch/Slow Twitch Muscle III. Muscle Fiber Types Fast TwitchSlow Twitch Lack myoglobin and are lighter in colorContains myoglobin and are dark in color Contain few mitochondriaContain many mitochondria Primarily anaerobic – does not need O 2 and produces lactic acid Primarily aerobic – uses O 2 and produces CO 2 and H 2 0 Fatigue easilyFatigue slowly Produce more forceful contractionProduce less forceful contraction Increase in size with trainingDo not increase in size