If you have access to an exercise bike or turbo trainer it is easy to estimate your fitness level using the calculator below. Simply measure your heart rate at 150 Watts and 100 Watts, enter the figures in the windows below, and hey presto! The higher the number, the better your fitness.
For accurate results, the following method is useful. You need a turbo trainer or exercise bike which will measure your power output in Watts, and a way of measuring your heart rate. When you first get on the exercise bike, pedal at a rate that gives you a power reading of 150 Watts. Continue for five minutes to allow your heart rate to settle, and then record your heart rate. Then pedal at a rate that gives a steady reading of 100 Watts for two minutes, then record your heart rate again.
The above method should give you consistent result. By using reasonably low power levels, you should avoid going anaerobic, which would give misleading results. Pedaling at 150 W first allows you to warm up. One useful tip - if you find it difficult to keep the power level constant, pedal in time with the music (if there is any in the gym!) and increase the resistance level on the machine until you reach the power level you require. This is actually a more accurate method as you are then pedalling at a constant speed. If possible use the same machine each time, as machines vary.
If you repeat this regularly through your training season, you will be able to chart your improvement in your fitness. Readings at an interval of a month or so are probably frequent enough, as otherwise fluctuations due to other things become dominant.
This method should be used to record your progress rather than to drive it. A sensible training program will be targeted at doing the Etape rather than achieving a particular power output!