The Challenge de la Lomagne - La Polastronnaise is a mountain-bike race series held in the Gers region of southwest France. It comprises four 30 km stages connected as a single challenge. The stages are La Mirandaise in Mirande, La Bikerienne in Beaucaire, La Colognaise in Cologne, and La Polastronnaise in Polastron, which concludes the series. Each stage provides a competitive race and a non-competitive randonnée option. The race begins at 9:30 AM, with randonnée riders starting shortly after.
Polastron is known for the series' muddiest and most technical terrain. One reported stage there attracted 212 participants, including 40 randonnée riders, on trails featuring a mix of faster rolling sections and more technical segments. Gravel and cyclo-cross bikes are prohibited, though electric bikes may participate in the randonnée but not the main competition. Post-race amenities include bike washing, showers, and refreshments, with awards presented at 12:15 PM. Now in its 26th edition, the challenge remains a local VTT event centered on villages, clubs, and riders who embrace cold, muddy trails.