Could be a confusion with semantics. Intervals are typically used to refer to timed or distance sets done at above LT, basically anaerobically and works the muscles more than the cardiovascular system. Tempo is used to call efforts at LT or slightly below, which works more on the aerobic system. It's not really possible to do a single workout that benefits both as optimally as doing intervals for the muscles and tempo for the cardiovascular system.
Depending upon where a particular rider is in his training and the types of events and performance he wants to achieve, you'd prescribe a certain amount and type of interval and tempo training.
A lot of people get stuck in no-mans-land of training and reach a plateau because they're doing both not enough intensity and not enough aerobic distance.
Last edited by Mothra; 07-18-06 at 12:21 AM.