Training for single speed and geared MTB racing

Question: How can you juggle the different training demands between mountain bike single-speed cross country racing and geared ultra-endurance racing? I want to be successful at both disciplines.

Answer: Training and racing shorter distances on a single-speed bike is first class preparation and training for ultra-endurance racing on a geared bike. Racing single-speed will strengthen your muscles and increase top end aerobic power. In your weekly training schedule plan your recovery rides and endurance rides on gears and your technical skills and shorter rides single-speed.
A great way to time your race season is to focus early season on single-speed cross country racing and schedule your higher priority ultra-endurance geared events later in the season. As the longer races approach on the calendar, taper down the amount of time spent on your single-speed and increase the amount of time on gears.
A great mid-season combo is to race a short track mid-week series event at max effort on your single-speed and do a longer race or training ride on the weekend with gears.
Cross country and short track single-speed racing exerts high forces on muscles and creates micro tears in muscle fibers. Schedule your final high effort single-speed ride 10-12 days out from your *A* priority ultra-endurance geared race to have strong muscles at full power on race day.