EX344 Exercise Metabolism

Aerobic Metabolism

The process of producing cellular energy involving oxygen, primarily utilized during rest and steady-state exercise.

ATP-PC System

A metabolic pathway that provides immediate energy through the breakdown of stored phosphocreatine (PC) to regenerate ATP during short bursts of high intensity exercise.

Lactate Threshold

The exercise intensity at which blood lactate accumulates significantly, typically occurring at 50-60% VO2 max in untrained individuals.

Excess Post-exercise Oxygen Consumption (EPOC)

The elevated oxygen uptake post-exercise to restore the body to pre-exercise conditions, formally replacing the concept of oxygen debt.

terminology reflects that only approximately 20% elevated O2 consumption used to “repay” O2 deficit

VO2 Max

The maximum rate of oxygen consumption measured during incremental exercise; it is a key indicator of cardiovascular fitness.

Glycolysis

The metabolic pathway that converts glucose to pyruvate, producing small amounts of ATP, and occurs both aerobically and anaerobically.

Lipolysis

The breakdown of triglycerides into glycerol and free fatty acids, primarily occurring during prolonged low-intensity exercise.

Metabolic Acidosis

The buildup of lactic acid in the body due to anaerobic metabolism, often leading to decreased muscle performance.

Respiratory Exchange Ratio (R)

The ratio of carbon dioxide produced to oxygen consumed (VCO2/VO2), used to estimate substrate utilization during exercise.

Crossover Concept

Refers to the shift from fat metabolism to carbohydrate metabolism as exercise intensity increases.

Glycogenolysis

The process of breaking down glycogen into glucose for energy during exercise.

Anaerobic Pathways

Energy systems that do not require oxygen, providing quick bursts of energy but yielding lactate as a byproduct.

Hypoxia

A deficiency in the amount of oxygen reaching the tissues, potentially contributing to the accumulation of lactate during exercise.

FATmax

The exercise intensity at which the maximum rate of fat oxidation occurs, just before reaching lactate threshold.

Ventilatory Threshold

The point during exercise where ventilation increases disproportionately to oxygen consumption, often corresponding to lactate threshold.

Glucose Pool

The available glucose in blood and tissue that serves as a key energy substrate during physical activity.

1 Met

is equal to the resting metabolic rate of an average adult, approximately 3.5 mL O2/kg/min.

oxygen deficit

lag in oxygen uptake at the beginning of exercise

3.5 ml/kg/min

is the amount of oxygen consumed per kilogram of body weight per minute at rest.

0.25 L/min

represents the oxygen consumption of an average adult at rest, equivalent to 1 Met.

250 ml/min

is the oxygen consumption of an average adult at rest, representing approximately 1 Met.

oxidative phosphorylation

is the metabolic pathway through which cells use enzymes to oxidize nutrients, thereby releasing energy to form ATP, primarily occurring in the mitochondria.

(VO₂ consumption at beginning of exercise is an indicator of energy supplied by ________)

Takes time for oxygen supply to reach muscle, and there is slow activation due to time for signals to activate rate-limiting enzymes

why slow activation of oxidative phosphorylation?

linear

HR + VO2 have a _________ relationship

high

EPOC > following ______ intensity exercise

-greater phosphocreatine

-greater concentrations of lactate in blood

-higher levels of epinephrine and norepinephrine

R

=VCO₂/VO₂

beta-oxidation

Fatty acids → acetyl-CoA

Krebs cycle

Acetyl-CoA combines with oxaloacetate (4 C) to form citrate (6 C)

Citrate is metabolized to oxaloacetate

Produces three molecules of N A D H and one FADH₂

One molecule of GTP is also formed (guanosine triphosphate)