Arvada, Colorado (United States of America) - "Ralston Creek Half Marathon & 5k". The Ralston Creek Half Marathon and 5K follow a mix of roads and bike paths on the west side of Arvada. The 5K is mostly flat and fast, with a small rise in the final mile. The opening four miles of the half-marathon are fairly flat, with a barely noticeable gradual gain in elevation. Miles 4 and 6.5 are rolling, with one good climb leading to the high point of the course atop Ralston Mesa. From there, the course is almost all down hill and flat to the finish. Aid stations every two miles. Finisher's medals for all half Marathon finishers. Prize money offered. The Ralston Creek Half Marathon & 5K is also the final event in the Racing Underground Winter Running Series with age group awards in every age category. Pick one race, or do all three! Series participants can choose the 5k-5k-5k Series or the 5k-10k-Half Marathon Series. Sartorious, 6452 Fig Street, Arvada, CO. www.racingunderground.com

Denver, Colorado (United States of America) - "Chilly Cheeks Winter Duathlon". The event starts with a 2.5M run with a 10M bike ride on paved roads and followed by another 2.5M run. The run covers a mix of road, paved bike path and well maintained dirt trails. Road bike and fat tire divisions are offered. New this year - a relay division. Post race hot food & drinks provided. Each entrant receives a pair of Chilly Cheeks Sweat Pants!!! Cherry Creek State Park, 4800 South Dayton Street, Denver, CO. www.racingunderground.com