Frame materials are selected with an aim to produce a lightweight, yet stiff and responsive frame. Low weight is prized for ease of carrying while running. A cyclo-cross racer may lift or carry his/her bike as many as 30 times in one 60 minute race, increasing the desire for a lightweight bicycle. Aluminum frames were popular in cyclo-cross bicycles long before they became commonplace on the road. Today the most popular material is aluminium with carbon fiber being popular at a professional level.