Question

Read the given statements and select the correct option :

1. Repeated activation of muscles can lead to fatigue.
2. Lactic acid accumulation by aerobic breakdown of glycogen causes muscle fatigue

• A. Both statements A and B are correct
• B. Statement A is correct but B is incorrect
• C. Statement A is incorrect but Statement B is correct
• D. Both statements A and B are incorrect

Answer 1

Answer:

B. Statement A is correct but B is incorrect

• Statement 1 is True: Muscle fatigue is a physiological phenomenon characterized by the decline in maximal force or power production capacity of a muscle during sustained activity. Repeated activation exhausts energy substrates (like ATP and phosphocreatine) and alters ionic balance, leading to a temporary inability to maintain the required force.
• Statement 2 is False: The assertion incorrectly attributes lactic acid accumulation to aerobic breakdown. Lactic acid (or more accurately, lactate and hydrogen ions) is a byproduct of anaerobic glycolysis (breakdown of glycogen in the absence of sufficient oxygen), not aerobic respiration.
• Understanding Muscle Fatigue Mechanisms:
  • Anaerobic Glycolysis: When oxygen demand exceeds supply during intense exercise, cells switch to anaerobic metabolism. This process produces lactate and H+ ions, leading to metabolic acidosis, which contributes to fatigue.
  • Aerobic Breakdown: Aerobic respiration (using oxygen) breaks down glycogen into CO2, H2O, and ATP. This is the efficient, primary energy system for sustained, lower-intensity activity and does not result in lactic acid accumulation.
  • Ionic Imbalance: High-intensity exercise causes potassium ion (K+) accumulation outside muscle cells and calcium ion (Ca2+) handling issues within the sarcoplasmic reticulum, which are critical factors in fatigue.