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