Energy Transfer During Exercise The Energy Systems

Energy Sources From Food: For Exercise: CHO = 4 kcal Fat = 9 kcal Pro = 4 kcal For Exercise: ATP > ADP + P

Methods of Supplying ATP For Energy Stored ATP CP or ATP-CP Anaerobic metabolism/glycolysis/lactic acid system Aerobic metabolism

ATP-PC System Intramuscular phosphagens Short anaerobic Uses stored ATP Strength/power movements Replenishes

Lactic Acid System Glycolytic Long anaerobic Burns glucose Accumulates lactate at high intensities Muscular endurance activities

Blood Lactate Threshold Exercise intensity at the point of lactate buildup. Predicts aerobic exercise performance. Untrained ~ 55% of VO2 max. Trained ~ 75% of VO2 max.

Aerobic System Oxidative Burns fatty acids Long-term energy Better butter burner Cardiorespiratory endurance activities

Energy Systems ATP-PC Glycolysis Beta Oxidation Stored ATP allows for 3-5 sec. of activity Breakdown of glucose – end result is pyruvate Breakdown of triglyceride – yields ATP ATP-PC used up in 10-15 sec. of activity Converted to lactic acid if anaerobic envir. > Fat oxidation = better butter burner

The Energy-Time Continuum As the work time increases, the percentage of energy contributed by the aerobic system increases.

Oxygen Uptake During Aerobic Exercise Increases sharply at onset Levels off within a few minutes if pace is constant (steady state) Oxygen demand met by supply

Maximal Oxygen Uptake (VO2 max) The region where oxygen uptake plateaus and does not increase despite an additional increase in exercise intensity.

Maximal Oxygen Uptake Affected by body size: larger size means larger VO2 max. Absolute oxygen uptake (ml.min.) Relative oxygen uptake (ml.kg.min.) Relative to body mass

Oxygen Deficit Difference between oxygen consumed during exercise and amount that would have been consumed had a steady rate, aerobic metabolism occurred at onset of exercise.

Oxygen Deficit: Trained vs. Untrained Trained reach steady rate quicker Higher total oxygen consumption Less reliance on anaerobic glycolysis Lower deficit in trained individuals due to: Earlier aerobic ATP production Less lactate formation

Excess Post-Exercise Oxygen Consumption (EPOC) Formerly called oxygen debt Excess oxygen above the resting level in recovery Most lactate does not synthesize into glycogen as originally thought Heart, liver, kidneys, and skeletal muscle use lactate as energy substrate during recovery

Active Recovery for Heavy Exercise Facilitates lactate removal because of: increased perfusion of blood through the liver and heart increased blood flow in muscles because muscle tissue oxidizes lactate during Krebs Cycle