Tempo running is a great session to hone a number of physiological determinants specific to long distance triathlon, one of the main ones being running economy. It's also a great skill to train to be able to maintain form at high speed with some fatigue in the legs. This session decreases rep duration, but increases rep pace. Starting at 6 minutes, the rep duration will descend to 4, 2, and then finish with 1 minute. However the pace will increase from 85% to 96% of threshold pace. Efficient and fluid running is key during this session as you change pace.