What does lactate cause?

Lactic acid or lactate is produced when the body does not get enough oxygen to break down glucose completely during high-intensity exercise or when there is not enough oxygen to meet the body's demands, such as during strenuous activity or in conditions such as heart failure or shock.

Lactate accumulation in the muscles causes a burning sensation and muscle fatigue, which can limit performance during high-intensity exercise. However, lactate is not considered harmful and can actually be beneficial in some cases, such as providing an alternative energy source for the heart and brain during intense activity.