7.4 - accumulation of metabolic by-products

How is glucose broken down in the anaerobic glycolysis system

• Muscular stores of glycogen are converted into glucose, which is then broken down into pyruvic acid (or pyruvate) with the help of enzymes

What happens to pyruvic acid when oxygen is not available in sufficient quantities

• pyruvic acid dissociates into lactate and H+ ions

• while lactate is no longer considered a major fatigue mechanism, H+ ions are

When does hydrogen ion (H+) accumulation occur during exercise

• when anaerobic glycolysis is the primary supplier of energy for ATP resynthesis

• when working at intensities above the athlete’s lactate inflection point (LIP)

How does the accumulation of hydrogen ions affect muscle cells

• increases the acidity within muscle cells (muscle acidosis), which reduces the muscle pH, making it difficult for the muscle to function properly

How does muscle acidosis impact ATP production

• Increased acidity inhibits the glycolytic enzymes responsible for breaking down glucose, reducing glycolysis and ATP production, which leads to decreased muscle force and power

What happens to exercise intensity as hydrogen ion accumulation increases

• As hydrogen ion accumulation increases, glycolysis slows down, ATP production decreases, and exercise intensity reduces, causing fatigue and a decrease in muscle force and power

What must a performer do once hydrogen ion accumulation occurs

• The performer will either need to slow down to actively recover or will experience exhaustion and have to cease exercising

When does inorganic phosphate (Pi) and ADP accumulation occur during exercise

• when there is rapid CP use during high-intensity exercise of short duration.

• ATP breaks down to ADP + Pi, and CP breaks down to creatine + Pi

How does inorganic phosphate (Pi) accumulate in muscles

• as a result of rapid ATP breakdown for muscular contraction and CP breakdown, both releasing Pi

How does ADP accumulate in muscles

• during periods of rapid ATP use, as ATP breaks down into ADP + Pi for energy during high-intensity exercise

How does the accumulation of inorganic phosphate (Pi) and ADP contribute to fatigue

• by interfering with the cross-bridge coupling cycle

• inhibiting myosin’s ability to generate force

• competing with ATP for binding sites on myosin, weakening muscle contractions