LT1, Aerobic Threshold, VT1, and FatMax are all metrics associated with exercise intensity. LT1 and Aerobic Threshold are often used interchangeably, though they are determined differently. VT1, unlike LT1, is measured with a metabolic cart instead of lactate samples. FatMax is the intensity at which fat combustion peaks and does not necessarily occur at the same exercise intensity as LT1.