The PBscience team recently contributed to the book Performance Cycling: the Science of Success, edited by Dr James Hopker and Dr Simon Jobson. Dan and Helen co-authored a chapter entitled Training with heart rate and power while Helen also contributed a chapter on Coach-athlete relationships. If you want to learn more about the PBscience coaching philosophy this is a good place to start.

Training Zones Calculator
Age in years
Maximum heart rate (MHR)
Zone Range BPM Purpose
Recovery Used for short (non-training) rides for recovery
Zone 1 For training rides of up to 6hr duration. Development of economy and efficiency with very high volume, low stress work. Very long sessions improve the combustion and storage of fats. Combine with Zone 2 for practical unstructured low stress rides.
Zone 2 For training rides of up to 4hr duration. Development of economy and efficiency with high volume, moderate stress work. An important intensity for establishing a firm base for all riders. Combine with Zone 1 for practical unstructured low stress rides
Zone 3 For training rides of up to 2hr duration. Development of aerobic capacity and endurance with moderate volume work at a controlled intensity. Should be done alone or in a small group to stay in zone. Possible (but boring) on a turbo trainer for up to one hour in bad weather. 'Modules' can be incorporated into Zone 1 or 2 rides to increase intensity whilst maintaining volume.
Zone 4 For training rides of up to 1hr duration. Typical 'mean' intensity of most road races. Useful for tapering and as preparation, to simulate race pace, rather than as training. Sessions should be ended when the effort starts to tell.
Zone 5 For training sessions of up to 40min duration. Raising of anaerobic threshold, improvement of lactate clearance and adaptation to race speed. Should be done alone and:-
(1) as a specific road or 'turbo' session or
(2) for controlled periods within a shortened Zone 1 or 2 session or
(3) in a 10 or 25 mile time trial.
Zone 6 For interval sessions of up to 20min duration (dependant upon intensity and rest/recovery periods). High intensity interval training to increase maximum power and improve lactate production or clearance. Probably best done on hills or a 'turbo' trainer.
NOTE 1. Should be done only when completely recovered from previous work.
NOTE 2. Heart rates are not the best guide for this type of training. Intensity should be such that the effort can just be held to the end of the interval. Ride on feel and use heart rate for feedback.