In a race the duration and intensity of effort cannot be controlled by the cyclist. The duration and intensity in a race are determined by the race distance and its development.
Just look at the heart rate curves during races in the youth category, the amateurs and pro cyclists. The intensity of effort in the youth category is amazingly high. The rider must – in order to be able to follow – constantly ride in the red zone. See the heart rate curves in chapter 5.
In a workout the intensity and duration can be controlled by the rider.
The intensity and duration of the effort may be monitored and adjusted with the help of a heart rate monitor and cycle computer. Nowadays the use of a power meter in order to analyze and adjust workouts is growing. A power meter measures the power output during the ride. Power is expressed in Watts.
In interval workouts intensive periods are alternated with recovery periods. The rider should strictly stick to the duration of the intensive part as well as the duration of the recovery period.
During intensive workouts there is an acidosis within the muscles. In training workouts the duration of the acidosis period remains under control because of the recovery that follows. During this recovery period this acidosis is neutralized.
The cyclist may well think that he can prolong the intensive part for a longer time but it would be wise te stick to the duration of the recovery periods.
On top of that this kind of intensive interval workouts should be well monitored so that the first and the last intervals are equal in quality. In this way the rider learns how to feel the signals of his body and how to dose his powers.