Philip Graves, 2009 UK champion in both Ironman and Ironman 70.3, uses big gear work to increase his bike power. His workouts aren’t complicated – he uses the longest hill he can find and pedals a big gear at a cadence as low as 40rpms, and he stays in the saddle. He also uses the turbo trainer to do one minute on, 30 seconds off, for a total of 20 repetitions.
At first you may want to start with 4x5 minutes at 55-60rpms, with a three-minute rest between intervals. This can be done either uphill or on a flat course, though it is typically easier when done on an incline. During these efforts, be careful not to let your heel drop too much, which can cause stress on the Achilles tendon. You should observe your heart rate during the workout, but it is not the main element. This is a muscular workout, not an aerobic one so you should feel fatigue in your legs, not your lungs.
Staying seated will help with your hip and back stability as well as your leg strength while standing helps to build the quadriceps. A stable back and hips are needed to create a solid platform from which you can generate power. When standing to power the pedals you specifically work your quadriceps, the main leg muscle that powers you along during a time trial. Standing helps to build maximum power output and is a key to building pure power. As a rule, short-course athletes should do 20-25 per cent of their efforts standing, while long-course athletes should reduce that to 5-10 per cent.
As you become stronger you can add time to your interval and drop the cadence to 50-60rpms. Short-course athletes should focus on becoming more explosive, keeping their intervals to 10 minutes, while Ironman-focused athletes will want to extend their time turning over a big gear to 20 minutes or more. Each session should end with at least 10 minutes of easy pedalling at your normal cadence.
A side benefit to the slower pedalling cadence is that it can help you smooth out your stroke. By performing the motion slowly you can feel your foot pulling through the bottom and coming over the top. This allows you to be more conscious of how fluid your pedal stroke is at those two critical points.