After half a century of confusion, researchers have a new perspective on the transition from "aerobic" to "anaerobic" exercise

In the running context, critical speed seems to be the better way of predicting marathon performance, as the recent data dump from Nike’s Breaking2 project suggested. But when I was reporting on Breaking2, the scientific team in charge was also interested in lactate threshold. The gap between lactate threshold and critical speed, they told me, gives you additional information about a runner’s strengths and weaknesses. Great marathoners have the two thresholds close together: they accumulate no lactate at all until they’re very close to their critical speed.