EXERCISE AND ENERGY
Contracting and Relaxing Skeletal Muscle
Whole Muscle Contraction
Graded response: Number of cells shortened (some vs.all) Frequency of contraction (twitch vs. tetanus)
Unfused tetanus Fused tetanus
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.
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
Muscle Fatigue
Muscles are physiologically unable to contract Lactic acid build up? Leaking of calcium?
Types of Muscle Contraction
Isotonic – filaments slide past each other & muscle shortens
Isometric – fibers tense but do not shorten
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
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
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