1. EXERCISE AND ENERGY Contracting and Relaxing Skeletal Muscle

2. Whole Muscle Contraction  Graded response:  Number of cells shortened (some vs.all)  Frequency of contraction (twitch vs. tetanus) Unfused tetanus Fused tetanus

3. Powering Contractions – ATP! Muscle cells only store ~4 sec. worth of ATP! 1. Aerobic respiration  Makes ~95% of ATP for muscles  Slow, requires oxygen 2. Anaerobic glycolysis  No oxygen available  Produces lactic acid 3. Creatine phosphate  Phosphorylates ADP.  Exhausted in ~15 sec.

4. Oxygen Debt  Prolonged activity  Lack of oxygen to muscle cells  Lactic acid accumulation  Low ATP supply  Must be “paid back” by breathing rapidly and deeply

5. Muscle Fatigue  Muscles are physiologically unable to contract  Lactic acid build up?  Leaking of calcium?

6. Types of Muscle Contraction  Isotonic – filaments slide past each other & muscle shortens  Isometric – fibers tense but do not shorten

7. Benefits of Aerobic Exercise  “With oxygen” – endurance  Stronger, more flexible muscles  Resistance to fatigue Increase blood supply to muscles Increase # of mitochondria  Improves metabolism  Improves digestion  Makes bones stronger  Enhances coordination  Improves lung and heart function

8. Benefits of Anaerobic Exercise  Resistance or isometric  Increase in size and strength  Muscles make more contracting filaments  Amount of connective tissue increases  Improved muscle tone – results from involuntary, scattered stimulation