The lactic acid that makes yogurt tangy is the same lactic acid that builds up in our muscles when we exercise strenuously. Instead of bacteria fermenting the sugar in milk to make energy for themselves, our muscles ferment sugar in our diet to produce energy to contract. If, like when we’re sprinting, lactic acid builds up in our muscles faster than it can be removed we can end up with a burning sensation in our muscles, forcing us to stop. Now if we train, we can increase the number of blood vessels in our muscles and clear out the lactate faster. For example, when researchers took some overweight sedentary women and started them on an aerobic training program of running and walking, at the end of three months, their lactate levels during exercise dropped 17%. But those on the same program who drank two cups of orange juice a day dropped their levels 27%. They did the same exercise program, but the citrus group experienced a significant decrease in blood lactate concentration, indicating an improvement in physical performance with less muscle fatigue. https://nutritionfacts.org/2014/05/06/citrus-to-reduce-muscle-fatigue/
