After exercising, Theo is aware that anaerobic respiration occurred in his body because his muscles ache. Which substance caused his muscles to feel sore?

During intense exercise, muscles may not get enough oxygen for aerobic respiration, so they carry out anaerobic respiration. This produces lactic acid, which can contribute to the aching feeling in the muscles. Glucose and glycogen are energy sources, while carbon dioxide is not the substance identified with this soreness.

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