Muscle Metabolism Muscle Metabolism Muscles need a constant

Muscle Metabolism

Muscle Metabolism • Muscles need a constant supply of ATP. • 3 Sources of ATP 1. creatine phosphate 2. aerobic respiration 3. anaerobic respiration

1. creatine phosphate + ADP → C + ATP • CP is a high energy compound stored in muscles in large amounts • CP reserves restored during inactivity by ATP not needed for muscle activity Creatine Phosphate + ADP C + P T A

2. aerobic respiration Requires Oxygen • glucose from bloodstream (from glycogen) → breaks down to release energy glucose + O 2 → CO 2 + H 2 O + ATP energy

3. anaerobic respiration • glucose → pyruvic acid w/out O 2 → lactic acid + 2 ATP • occurs when circulatory system can no longer deliver enough O 2 • causes most pyruvic acid to change to lactic acid – makes muscles sore • most lactic acid diffuses from muscles into bloodstream • when O 2 is available, lactic acid is reconverted to pyruvic acid and either oxidized or converted to glycogen

• Although aerobic harvest 20 x more ATP/ glucose, anaerobic produces its ATP 2 x faster. • When large amounts of ATP are needed for moderate periods (30 -40 sec. ), the anaerobic can provide most ATP. • stored ATP + CP + LA glycolysis = high exertion for about 1 min.

Energy Systems Used During Various Athletic Activities • ATP and CP - used when activities require a power surge last only a few seconds ex: wt. lifting, diving, sprinting • anaerobic - sustained, less vigorous activities ex: tennis, soccer, 100 m swim, soccer • aerobic - prolonged activities that need endurance, no power ex: marathon runs, jogging

Muscle Fatigue • when ATP production cannot keep pace with ATP use • when muscles fatigue, they do not respond to stimuli (cross bridges do not detach)

Other Fatigue Factors Include: Lactic acid build up not due to inadequate gas but heart can’t keep up or muscles can’t handle more O 2 Ionic imbalance of Na+ - K+ pump in absence of ATP, pump doesn’t work right, active transport Oxygen debt

Oxygen Debt • incurred during anaerobic respiration • must be repaid • extra amounts of O 2 must be taken in by the body to provide for restorative processes

Oxygen Debt • represents the difference between the amount of oxygen that would be needed for totally aerobic respiration during muscle activity and the amount that is actually used Increased breathing reduces oxygen debt

All or None Response • muscle fibers contract to the full extent of their ability or not at all

Speed and Duration of contraction depends on: 1. size of load greater loads = slower contraction 2. muscle slow fast fiber type twitch - slow but fatigue resistance twitch - quick but tire (need more oxygen) twitch - quick but resistant to fatigue • Muscles are a mix of fast and slow (% is genetic).

Muscle Hypertrophy • Endurance does not promote hypertrophy. • Hypertrophy is from high resistance exercises. # of myofibrils increases

Muscle Atrophy • Immobile muscles will atrophy. # of myofilaments decreases

Effects of Aerobic and Resistance Exercise on muscles and other body parts • capillaries around muscles increase • mitochondria increase • less fatigue • increase in strength • body more coordinated • improved digestion • skeleton stronger • improved cardiovascular system • burns more calories