The tibia and fibula are the two bones found in the human leg. The tibia, also known as the shinbone, is the larger and stronger of the two bones and is located on the inner side of the leg. The fibula is the smaller bone and runs parallel to the tibia on the outer side of the leg.

lactic acid is one of the end products of anaerobic respiration in humans and some other organisms. During anaerobic respiration, which occurs in the absence of oxygen, glucose is partially broken down to generate energy. In the absence of oxygen, cells can convert pyruvate, a product of glycolysis, into lactic acid. This process, called lactic acid fermentation, helps generate energy in the absence of oxygen but also leads to the accumulation of lactic acid, causing muscle fatigue and soreness.