Jaina just got home from a difficult workout. She is complaining of muscle soreness and cramps. Which waste product of fermentation caused the soreness and cramps?

The answer is lactic acid/lactate. This is caused by anaerobic respiration in muscles especially during strenuous physical activity due to low oxygen supply to muscles in respect to the demand. When there is sufficient oxygen in the muscles, pyruvate is broken down aerobically in the Kreb’s cycle. However, it is converted to lactate in the anaerobic pathway. Lactic-acidosis occurs when lactic acid accumulates in tissues and slows down metabolic pathways