Define Power

Power is the rate at which work is done. Since work equates to a certain amount of energy expended, power is a rate at which energy is produced or expended.

In a physical sense, work is required to move something over a fixed distance (force x distance).
Power, being the rate at which work is done, is force x velocity. On a bike that equates to force on the pedals times the rate at which the pedals are being moved.

It takes a certain fixed amount of work to move a bike and rider to the top of a mountain. That work is being done by the muscles, and each little cell is converting energy from food into work done on the pedals. The amount of energy that can be converted each second is limited by the physiological composition of the cell (ie, how many mitochondria), rate of O2 delivery to the cell, availability of fast chemical energy like ATP as opposed to fats, etc. More energy converted each second means more power on the pedals. It takes twice as much power to get to the top of the mountain twice as fast, since the rate of work has been doubled.

Things like pH changes, fatigue, bonking, etc. affect the amount of energy the cells can produce, or interfere with their ability to contract and do useful work on the pedals.

Strength, as in weightlifting, is the ability to generate a large amount of static force. Cyclists are hardly ever called upon to generate a large amount of static force. Most of the time they are producing a small amount of force many, many times per minute. It's the rate that that force can be generated which makes power the limiting factor for cycling, as opposed to strength.

tdl123321 said:

When one says he wants to increase power, I naturally think of strengthed muscles(such as weight lifting), but the adaptations that I've read about on this forum(ex:increasing LT) seem to be more cardiovascular in nature. I guess my question is: What changes actually provide an increase in power. Leg muscle hypertrophy, cellular changes within the muslce(ex; increased mitochondria), improved cardiac/pulmonary efficiency, etc?

With cycling, there are so many different kinds of power as well...It isn't just merely being able to produce more power. The best way to get an idea of this is to look at a critical power graph (CP1, 2.5, 5, 10 minute powers). Although all the different power amounts are related, they are still somewhat independant of each other. This means that if you want to improve your sprint power, pick a training route with a lot of red lights and stop signs... If you want to produce more long duration power, work on LT intervals, or 10-20 minute intervals. Just work on where you want more power. Different things happen in different areas...Your max 1 minute power involves much more fast twitch muscle fibers; more strength, whereas your max 20 minute power is much more aerobic and relies on your cardiovascular system more. The other guys in this forum have a much keener knowledge of the specifics than I do, but I think that might help