We're entering the month of March and as we have seen in past years, nothing challenges our local athletes more than tests of endurance. In March alone, there will be four great tests of varying skills. March 6, the Audi Power of Four tests skiing and mountaineering skills, as participants climb up and ski down all four mountains in the Aspen Snowmass resort. The next day, March 7, will see the annual cross-country ski races of the Owl Creek Chase. The 19K race starts at the Aspen Nordic Center and finishes at the AVSC center. Aspen hosts the America's Uphill race on March 13 - a 2.5-mile, 3000 vertical-foot climb up the face of Aspen Mountain. Participants ski, run and snowshoe up the steep front face of the mountain with groups starting every 30 seconds to spread out the crowds. And finally, the endurance granddaddy of them all, the Elk Mountain Grand Traverse will be held March 27-28. Participants race in teams of two starting at midnight in Crested Butte, and arrive the following morning in Aspen, having covered 40 miles and 6800 vertical feet in the Elk Mountain range.