But regardless, Yasso 800s remain a classic workout – and now there may be an equivalent for the half marathon. If it’s a 1 hour 30 minute half marathon you’re after, run the reps in 1 minute 30 seconds. In physiological terms, the Yasso formula equates closer to threshold pace, which is a better predictor of marathon (and half marathon) times. ‘So I wouldn't necessarily recommend basing your half marathon pace on this session because the pace is quite hard. Related Story 12 Tips for a Sub-2-Hour Half Marathon