Kiwiboy:
First, there are many, many different strategies for doing intervals. Length, pacing, number, frequency, intensity, are some of the considerations when designing a plan.
Basically you should start with the hardest, most intense efforts first. You should throw a few 3-5 minute time trial efforts in there also. If you are riding in a small group, have every member take a 3-5 minute pull at a pace so high that you can barely get back on the last man's wheel when you pull off. Repeat 2-3 times. If you are training alone, recover for at least 5 minutes between efforts.
When you are talking about speed and going fast, you are talking about short, high-intensity efforts. Longer efforts like 20-30-60 minutes have their place, but the problem is it takes longer to get faster, and you may plateau at a certain level, below what you are truly capable of. Short, hard efforts are the best way to break out of this rut. 10 seconds to 5 minutes works real well.
For better strength, do the big-ring low cadence efforts on the hills instead of the flats.
For additional overload, I like to do short "stomp" intervals at the end of speedwork sessions. The prior efforts will leave my legs very tired, and from a moderate roll(15-20 mph) I'll wind up a 53x13 or 53x12 seated and as rapidly as possible, accelerate to 30-31-32+ mph and hold it for as long as possible, usually 5-30 seconds. Sometimes I'll use an 11 cog for more strength. Do this a few times. Training like this simulates a finishing effort at the end of a race, when your legs are also tired. Very important, STAY SEATED for the entire effort.
Short efforts are harder on the body, and care must be taken to ensure propery recovery, but the results are well worth it. After a while, you will be able to increase sustainable power, and you will be able to sprint at high speeds repeatedly, one of the hallmarks of a powerful racer.
If you are racing on the weekends, one of these sessions per week is plenty, unless your body has excellent powers of recovery. Vary your training also. After 2-4 weeks of short stuff, go longer and slower for a week or two. If you get too tired, take an easy week. If your body is smoked, it is still recovering. Still recovering means still growing, so don't rush it. When you fully recover, you will be faster than ever!!!
I noticed you included a warm up, but made no mention of a cool down. Don't blow this off!!! Cooling down is very important. You will feel much better if you cool down for at least 15-20 minutes in the small ring going slowly. Always cool down when training hard!!!
Good luck!!!
