CSCS Chapter 3-Bioenergetics of Exercise Training

Bioenergetics

How the body transforms food energy into biological work (movement, heat).

Metabolism

Sum of all anabolic (building) and catabolic (breaking) reactions.

Catabolism

Breaking down molecules to release energy.

Anabolism

Building larger molecules using energy.

Exergonic Reaction

Releases energy (downhill).

Endergonic Reaction

Requires energy input (uphill).

ATP (Adenosine Triphosphate)

Immediate energy currency for muscular work.

ATP Hydrolysis

ATP → ADP + Pi + H+ + energy (power stroke contraction).

ATP Resynthesis

Re-forming ATP from ADP via energy systems.

Phosphagen System

Extremely High Intensity

0-6 sec

Phosphagen and Fast Glycolysis

Very High Intensity

6-30 sec

Fast (anaerobic) Glycolysis

High Intensity

30 sec-2 min

Fast Glycolysis and Oxidative System

Moderate Intensity

2-3min

Oxidative System

Low Intensity

Greater than >3 min

Glycogen

Storage form of glucose in blood

Muscle and Liver

Glucose

6 carbon molecule

Hypoglycemic

low blood sugar

Hyperglycemic

high blood sugar

Anaerobic Fast Glycolysis

metabolic process in which cells quickly break down glucose into pyruvate and then into lactate to produce ATP, the energy currency of the cell, without oxygen occurs in Cytoplasm outside of the cell

Glycolysis

Cellular process of breaking down glucose into pyruvate, a three-carbon molecule, to produce energy in the form of ATP and NADH

Fast (Anaerobic) Glycolysis

Glucose is broken down into pyruvate, which is then converted to lactate, allowing for the rapid production of energy . Occurs in cytoplasm outside of cell

Lactate; predominant ~15-60 s high-intensity.

Slow (Aerobic) Glycolysis

Glucose is broken down into pyruvate in the presence of oxygen, allowing the pyruvate to enter the aerobic system for sustained, higher ATP production. Occurs in Mitochondria

Pyruvate → acetyl-CoA → enters Krebs; lower power, longer duration.

Lactate

Also known as lactic acid, is a byproduct of cellular metabolism. It is produced when the body breaks down glucose (sugar) for energy without enough oxygen present

Lactate Dehydrogenase

Enzyme found in various tissues throughout the body. It plays a crucial role in the conversion of lactate to pyruvate, a process known as anaerobic metabolism

Cori Cycle

Also known as the Lactic acid cycle, is a metabolic pathway where the Liver converts lactate, produced by muscles during anaerobic respiration, back into glucose

Metabolic Acidosis

Burning sensation due to accumulation of Hydrogen ions H+ from ATP hydrolysis decreases pH and contributes to fatigue.

Oxidative System

Uses carbohydrate, fat (and minimal protein) to produce ATP in mitochondria.

Krebs (Citric Acid) Cycle

Occurs in Mitochondria requiring oxygen, pyruvate loses carbon and becomes Acetyl coA and generates 2 ATP

Oxidative Phosphorylation

The production of ATP using energy derived from the redox reactions of an electron transport chain; the last and major stage of cellular respiration.

Aerobic Glycolysis 2 net ATP

Krebs Cycle 2 net ATP

Oxidative Phosphorylation 34 ATP

Substrate Use with Intensity

As intensity increases, carbohydrate reliance increases; fats dominate at low intensities.

Oxygen Deficit

Early exercise when O2 supply lags behind demand.

EPOC

Elevated post-exercise O2 consumption to restore homeostasis and fuels recovery. up to 10-15% extra cal burn

Lactate Threshold (LT)

First rise in blood lactate above resting;

50-60% VO₂ max untrained

70-80% VO₂ max trained

OBLA

Onset of blood lactate accumulation at ~4 mmol·L⁻¹.

physiological point during exercise where blood lactate levels begin to increase rapidly above resting levels, even when the body attempts to clear it, casuing fatigue.

Glycogen Depletion

Occurs when the body's stored carbohydrate (glycogen) is used up. Markedly reduces high-intensity performance; "hitting the wall" in endurance events.

Gluconeogenesis

Metabolic process of creating new glucose molecules from non-carbohydrate sources, such as Lactate, Glycerol, and Amino acids. This process is essential for maintaining blood glucose levels, especially during fasting, and primarily occurs in the liver and kidneys.

Interval Targeting Phosphagen System

90-100% max power

5-10 sec

1:12 to 1:20

Interval Targeting Fast Glycolysis

75-90% max power

15-30 sec

1:3 to 1:5

Interval Targeting Fast Glycolysis/Oxidative

30-75% max power

1-3 min

1:3 to 1:4

Interval Targeting Oxidative

20-30%

Greater than 3 min

1:1 to 1:3