definately nordic skiing, and biathlon specifically. nordic skiing is a quadrapedal sport, which means that the athlete uses all four of their limbs to create propulsion, compared to two in nearly every other sport. combine that with the constant compression of the abs which are used in the v1 and double pole techniques-the 2 most used techniques, and the distances covered by the athletes (sometimes over 100km per race)nordic skiing is by far the most physical sport. nordic biathletes in particular must be in extreme control of their bodies durring competition, because they ski, raising their heart rate, then have to lower their hart rate in a minimal amount of time to shoot extremely accurately, in not only prone, but also standing positions. standing, not to mention, on skis.