Understanding Power

I've read just both editions of the Hunter Allen book on power and they are both great books. I've also read Joe Friels book that just came out along with several other books on training that touch on power. In my own training and in working with other cyclists I really enjoy using power as a barometer of fitness. It is possible, in my opinion, to get lost in the data. I belong to a couple of coaching forums that have memebers who are really into dissecting the data to a level that really doesn't interest me. At the same time there is a basic understanding of the information that is important to everyone using a power meter. As much for my own benefit as the followers of this blog (and we're closing in on 6000 views in the last 12 months) I thought I'd go through some of the basic terminology. I'll be referencing the Allen and Friel books pretty exclusively. If you don't own them, I would recommend buying them. So what is power? Simply put it is equal to Work divided by time or P=W/t. What is work? W is equal to force times distance or W=F x d From these equations we can say that P= F x d/t Taking this a step further we can say that distance divided by time equals velocity so P=F x v. For cyclists this comes down to power being equal to how big a gear we can push at how great a cadence. We can apply more force at a steady cadence, pedal faster at a steady force or increase both. I wont get into the true definition of a watt as I don't understand the equation but simply put it's a measure of power and when compared to our weight in kilograms offers endless discussion among cyclists. Another number shown on most power meters is KiloJoules, or mechanical energy. Essentially the Kj is equal to a calorie by way of this reasoning: a Calorie (capital C) = 1000 calories or kiloCalories. If we know that 1 kiloCalorie equals 4 kilojoules and humans are about 25% efficient this means that about 1/4th of the energy we create is converted to energy on the bike known as kilojoules. If we're 255 efficient, then the 1 kiloCalories is equa lto about 1 kilojoule. Thankfully, someone else figured all this out and we really just need the end result numbers for training and fueling purposes.