General participation in contests such as ultra-marathons and ultra-triathlons has increased considerably over the past 30 years, especially among women. This study investigated performance trends in the ‘Swiss Bike Masters’, one of the first and most prestigious mountain bike ultra-endurance races in its class, with comparisons of participation and performance trends to similar races. The development of performance in the ‘Swiss Bike Masters’ held between 1994 and 2012 was investigated by analysing the number of finishers, their age, sex and cycling speed. Between 1994 and 2009, the athletes had to cover 120 kilometers with a total difference in altitude of 5,000 meters. Since 2010, the race distance was shortened to 105 kilometers and the total difference in altitude was reduced to 4,400 meters. The total men participating and total finishing decreased significantly, while women’s participation has remained low. The age of the annual winners and the annual top three finishers showed no changes over time. Performances of the annual fastest women improved while performances of the annual fastest men remained unchanged. To summarize, rate of finishing has decreased for men and has been stable but low among women. The sex difference in cycling speed for the best cyclists has decreased across the years.