I think it boils down to efficency. Higher turnover ultimately = higher speed. Also from a injury preventative side, higher turnover ( by way of smaller strides) helped me lessen the impact on my heel strike as i used to over extend when I got into a groove. This caused some serious shin splints over time that needed a physios attention to get worked out.

Right, you can look at it as either 180 bpm for each step, or 90 bpm for one leg (i use the right leg to count off).

It takes time to get used to that running cadence. Start out from your normal routine and if you can, bring a metronome or pace-beeping watch. I found one at LaCrosse Technology which also has a count-down timer as well as a compass. (never know when you're going to need a compass ;) ) Anyway, I picked it up somewhere around $25 US.

Then the cool thing I learned while doing this is that you can increase /decrease your speed by the amount of forward lean. It also works if your heart rate is starting to redline. Just lean back and your size of steps should reduce while still maintaining the pace count.

Hope that helps,
-Brandon

Yeah, 90rpm should be all the time. I read a study where they analyzed the cadence of a something like 400 Olympic and amateur athletes, for both sprint and long distance, and the most efficient people energywise were all running at the 90rpm range.

Speed is just varied through your stride length. Try lengthening your stride going downhill to help you increase your speed on the flats, and shorten that stride on the uphills to keep up your cadence.

This idea of increasing your turnover was a huge concept that my high school cross-country coach worked around and seemed to help me immensly. The big drill I remember and still use to this day was counting your turnover per minute or per 200m if we were on a track (easier to not let your timing not interfere withh your counting) and then try to to increase that number by 10-15 and then depending on your level and where you are, try to increase that number again and again while holding your pace, trying to get closer to 90 rpm, once you adapt to this faster turnover, you'll find your natural stride length. I'm from a running background and will probably be a runner long after my competitive triathlon era has passed, so I practice form drills such as improving cadence, and strides and other drills at least once every two weeks and I think I see huge benefits from this. One of the keys to downhill running is to increase your cadence, with lots of small quick steps, it will increase your speed as well as reduce much of that down hill impact.