Lactic acid
Lactic acid (C3H6O3) is the byproduct created by the Human body, formed when the body breaks down glucose to obtain energy, as a result of light muscle strain.

The Doctor monitored a gradual build-up of lactic acid in Kathryn Janeway's extensor muscles during her Nechani endurance ritual in 2373. ()

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de: Milchsäure
Biochemical compounds