Michael Hanslip Coaching

If you want to go faster, you have to pedal harder

Training trade-off

One of the unbreakable rules of fitness is that you must trade fitness for speed. No matter how you look at it, no person can do as much high intensity work as they do low intensity work. And it is the volume of work that determines fitness. In preparation for racing, or a specific race, winding back the volume to add intensity means winding back the fitness to introduce some speed. So you should "mean it" when you do it.
I'm writing this watching a ProTour event and I think one of the reasons they are SO fast recently is that training has changed to be far less about speed and far more about fitness. A large aerobic base can carry a cyclist at a high velocity without any actual speed work. And it can carry a cyclist through the grand tours better. There are a lot of things that go with this, so it is a separate topic, but the take-away message is that the more volume you do, the fitter you get. And to do more volume, without injury, means doing it at lower intensity.
 
Fortunately, you can add some good speed with as few as six sessions in the lead up to whatever you want to be fast for. And racing involves intensity - so you can get your speed "for free" if you don't mind underperforming in the early races.