1. Muscle Metabolism Aerobic respiration: produces large amounts of ATP but requires O 2 to function, waste products: water, CO 2 Anaerobic fermentation: produces small amounts of ATP in absence of O 2 waste product: lactic acid (major factor in fatigue)

2. Muscle Metabolism There are three phases to muscle metabolism Each is designed to give muscle tissue energy during strenuous activities

3. Muscle Metabolism 1.Immediate energy: during intense exercise oxygen is quickly depleted in muscle(6sec) so ATP is made by grabbing Pi from donor molecules and adding it to ADP to make ATP Donor molecule: Creatine kinase grabs a Pi from creatine phosphate (CP) and adds to ADP to make ATP, nearly all ATP during short burst are produced this way (phosphagen system)

4. Muscle Metabolism 2.Short term energy: once the phosphagen system is depleted the body goes into anaerobic respiration. It can generate energy for 40 sec in intense activity 3.Long term energy: after 40 sec the body cardiovascular system catches up and is able to deliver the needed oxygen to the muscles for aerobic respiration

5. Fatigue Fatigue: the gradual weakness and loss of contractility ATP production decreases as glucose is used up Low levels of ATP slows Na/K pumps Lactic acid inhibits ATP production K+ in the ECF makes cell less excitable ACh becomes depleted

6. Oxygen Debt Oxygen Debt: occurs after exercise. Due to the following Oxygen reserves: oxygen is dissolved in tissues in the body that are depleted first and need to be replaced Phosphagen system: ATP must be made, then broken to give Pi back to creatine Oxidizing lactic acid: most of lactic acid will be converted into glucose in the presence of oxygen Metabolic rate: if body temp is high the metabolic rate is high and requires oxygen to break down molecules

7. Muscle Fibers Slow oxidative (SO): Red fibers with lots of mitochondria and blood capillaries better for aerobic activity Fast glycolytic (FG): White fibers with large storage of phosphagen and lactic systems better for quick responses but not endurance