Which organic acid is formed in muscle tissue during strenuous exercise and massage?

• A. Lactic acid
• B. Acetic acid
• C. Citric acid
• D. Malic acid

Answer: (A)

When muscles are pushed hard and oxygen delivery is limited, they rely on anaerobic glycolysis to keep producing energy. In this pathway, pyruvate is converted to lactic acid (lactate), which helps regenerate NAD+ so glycolysis can continue. This lactic buildup in muscle tissue is what’s typically associated with fatigue and the burning sensation during intense effort. Massage can aid recovery by increasing circulation and lymphatic flow, helping to move lactate and other waste products away from the muscle tissue. The other acids—acetic acid, citric acid, and malic acid—are linked to different parts of metabolism (fermentation, and the Krebs cycle, respectively) and aren’t the primary products formed in muscles during strenuous anaerobic activity.