lactate shuttle

The production, exchange and utilization of lactate into the blood stream. Some of the lactate is released into the blood stream and used directly as a fuel by heart muscle, and by the liver to produce blood glucose and glycogen. There is general agreement among many physiologists that the lactate shuttle is a major means of providing energy and material for gluconeogenesis. It has been estimated about 50% of the lactate produced during intensive exercise is used by muscles to form glycogen; this glycogen acts as a metabolic fuel to sustain exercise.