Performance cyclists do not necessarily need to own a power meter to train effectively. Training schedules based on heart-rate, Relative Perceived Exertion (RPE) or time dependent measurements can provide an adequate means for assessing training volume and intensity, especially when supplemented with well conducted and reproducible physiological assessments to measure, adjust and steer the programme in the right direction.
Training with both a power meter (direct power as opposed to derived power) and a heart rate monitor allows for an ideal combination of the objective measure of exercise intensity and an indirect measure of oxygen consumption. Although interpreting the data can be a daunting task, and can take valuable time to process. The comparative value of the power: heart rate ratio and its relative relationship changes over time, offers excellent insight into how a rider is responding to a training plan and incremental progression in performance without over-loading the individual and reap maximum effect. Riding at the same power output with a lower heart rate is an indication of improved fitness assuming a relative lowering or no change in RPE. An increase in perceived exertion with lower heart rate would suggest fatigue, especially if the rider is unable to sustain a particular power and previous sessions were indicative of a poorer performance.
The response to a training stimulus (the Impulse-Response) is highly individual, as any one session will affect each athlete in a different way as dictated by genetic determinants of a cyclists physiology. The scientific approach is to apply the concept of a preferred periodisation model (targeted systems (traditional), block or polarised, depending on lifestyle) in a personalised manner and achieve peak performance for the required event.