Skeletal Muscle Metabolism How do muscles use energy

Skeletal Muscle Metabolism How do muscles use energy?

WHAT IS Chemical compound used to trap energy from food

ATP Mitochondria in muscle convert glucose, fatty acids, and amino acids into ATP n ATP is used by the cell for any process that requires energy (such as muscle contraction) n The amount of oxygen available to the muscle cells determines the amount of ATP that can be produced n

ATP Adenine P P P 3 Phosphate groups Ribose

ATP Adenine ENERGY stored in bonds P P P 3 Phosphate groups Ribose

ADP ATP P P ENERGY RELEASED PP

Sources of ATP (times approximate) • Stored ATP from processes below (4 -6 seconds worth) • Creatine Phosphate (10 seconds) • Glycogen (stored carbohydrates in liver and muscle) or glucose in blood are used for glycolysis and lactic acid fermentation (30 -40 second bursts) • Glycogen, glucose, fatty acids are used in aerobic respiration (lasts for hours)

Glucose from glycogen in muscle and liver O 2 Glycolysis No O 2

Summary: With or Without Oxygen? Without oxygen (anaerobic) With Oxygen (aerobic) n Glycolysis (splitting of n cellular respiration using glucose) follow by glucose, fatty acids, or amino fermentation of lactic acid) acids (preceded by glycolysis) n ATP produced quickly n ATP produced slowly n Fewer ATP are generated n More ATP generated n Duration: 30 -60 seconds n Duration: hours

Muscle Fiber Types Slow-oxidative - endurance activities (jogging) (smallest diameter) n Fast - oxidative - short term activities requiring bursts of energy (sprinting, basketball, soccer, etc. ) n Fast-glycolytic - short intense movements where force production is maximal (lifting heavy weight, jumping, throwing) (largest diameter) n

• All muscles are a mix of different fiber types • Genetics determine the percentage of different fiber types in different muscle

Fatigue and Oxygen Debt Occurs when ATP demand is faster than production (when O 2 supply is limited) n Lactic acid “burn” limits usefulness of ATP n Oxygen Debt - the amount of O 2 that must be taken in to restore the muscles’ resting conditions (ATP regeneration, glycogen replenishment, creatine phosphate restoration, lactate breakdown) n

Muscle Fiber Ratios and Athletic Performance n n Which of the above athletes have a greater composition of fast twitch muscle fibers? How does this relate to athletic performance?

Hypertrophy - increase in the size of a muscle n n Micro-tears (of the myofilaments) create a stimulus for hypertrophy. Stressed fibers form more myofibrils, myofilaments (actin and myosin), and store more glycogen (fast-twitch more prone to growth)