Brosse was born in Le Pont-de-Beauvoisin, Savoie. He started ski mountaineering in 1990 and competed the first time at the Miage Contamines Somfy race in 1995. In 1996 he became a member of the national team. Together with Pierre Gignoux he set the record and continued to hold it for the Mont Blanc course from 30 May 2003. The duo needed a total time of 5h 15' 47 for the total course, thereof about 4 hours and seven minutes for climbing up, and about one hour and seven minutes for the downhill race. Since 2003 he and Lionel Bonnel had also held the Chamonix-Zermatt Haute Route record with 21h 11'.