Whtever your sport, ( ok - lets pick cycling...) intense or interval training (as per VdV) above is definitely a powerful method if you/your coach know what you're doing. Takes way less time and avoids injuries caused by over-training - not to mention keeping mental sharpness up. I have no idea how widely this is used in cycling but its increasingly common in swimming for instance. Remember the American woman at the last Olympics who made a comeback after having kids? Claimed that she barely swam more than an hour a day, more focussed on flexibility, nutrition etc.... Takes a lot of balls to do that when your competitors are putting in 6km or more per session in their heavy training periods. She also had the benefit of a technique that had already been developed to an elite level - technicque is not to be underestimated.

Lance & Cadels books give some insight into their training. Lots of cycling BTW. I'll see if I can pick up some of the key points and add them later.