The guy's been kicking ass all over the world won another 10K this past weekend. Post race he said, "The last 4km is the toughest stretch of the course and I let it roll, letting the hills do the work". There was no further context. What does this mean in terms of strategy, approach & technique? btw, he's racing here in nyc at the end of may in a 10k to defend his title (set course record last year).