Metabolism and Exercise Where do Muscles Get their energy? · ATP - adenosine triphosphate Skeletal Muscle Physiology muscles only store 4-6 seconds worth · ATP ADP + P Part 2 - Metabolism & Exercise · 3 pathways turn ADP back into ATP direct phosphorylation by creatine phosphate (CP) anaerobic respiration aerobic respiration Creatine Phosphate Anaerobic Respiration · CP - unique high-energy molecule stored in muscles · glycolysis - glucose breakdown · can directly transfer energy and a phosphate to ADP glucose pyruvic acid + 2 ATP · 14-16 seconds of stored ATP and CP · can occur with or without oxygen used in surges of activity lasting only a few seconds oxygen present - pyruvic acid enters weightlifting, diving, sprinting mitochondria for aerobic respiration · CP reserves restored during inactivity or rest oxygen absent - pyruvic acid converted into lactic acid CP + ADP creatine + ATP · together, stored ATP & CP, and glycolysis can support muscle activity for about a minute used during on-and-off or burst-like activities tennis, soccer, swimming Aerobic respiration Muscle Fatigue · occurs in mitochondria · physiological inability to contract even though · requires oxygen and glucose muscle may still be receiving stimuli · glucose comes from... · possible causes muscle glycogen problem in E-C coupling bloodborne glucose neuromuscular junction pyruvic acid (glycolysis) ionic imbalances (potassium) fatty acids (after about 30 minutes) pH increase due to lactic acid build-up · used during endurance activities (jogging) · ex. writer's cramp glucose + oxygen carbon dioxide + water + lots of ATP Metabolism and Exercise Oxygen Deficit Types of Muscle Fibers · for a muscle to return to its resting state, it must... · classified by their speed of contraction and major replenish oxygen, ATP, and CP reserves pathways for forming ATP convert lactic acid back to pyruvic acid · slow oxidative (SO) fibers (red in color) replace glycogen contraction - slow · during anaerobic respiration, there is not enough ATP production - aerobic oxygen to accomplish all this so it is deferred until used in endurance activities · oxygen is present fast oxidative (FO) fibers (red to pink) · oxygen deficit - extra oxygen the body must take in contraction - fast ATP production - aerobic/anaerobic to restore muscles to their resting states sprinting, walking · fast glycolytic (FG) fibers (white) contraction - fast ATP production - anaerobic used in short-term intense or powerful movements Muscles & Excercise · endurance exercises increase stamina (resistance to fatigue) more efficient muscle metabolism swimming, jogging, biking, fast walking · resistance exercises increase strength increases size of individual muscle fibers weight lifting.