anything done or to be done; anything requiring action or effort; business; concern: an affair of great importance. 2. affairs, matters of commercial or public interest or concern; the transactions of public or private business or finance:
Hyperlactatemia is defined as a persistent, mild to moderate (2-4 mmol/L) increase in blood lactate concentration without metabolic acidosis, whereas lactic acidosis is characterized by persistently increased blood lactate levels (usually >5 mmol/L) in association with metabolic acidosis.
Your body has to clear the lactate from the blood and working muscles and process it back to useable fuels, and lactate threshold is the point at which production outstrips the clearing process and higher levels of blood lactate start to accumulate in the muscles.