The crank must be a solid component because it must resist your full force when kicking away from the lights, or attempting that skid. It also must resist your mass when landing that jump and, for the careless, also resist ground strikes when cornering. The more technically minded might notice the fact our cranks are still, on the whole, square taper. This is not reactionary. Part of it is that square taper cranks lived on with the track for longer than the road. It is also considerably easier to get the chainline correct with square taper, such is the range of bottom brackets available. And the long period of time over which square taper was the top choice means a considerable legacy of high quality square taper cranksets are yours for the taking at cycle jumbles.
Tech-wise, the square taper falls into two camps: the ISO used by European manufacturers of old but currently only on some Sugino and Campagnolo, and the considerably more popular JIS (Japanese) type used on most everything mass market. Both types are in practice interchangeable, at a pinch, but it will put the chainline out from the manufacturer's specification. Chainwheels need to have the correct bolt circle diameter as the crank, and (obviously) the same number of holes. Most crank sets come with 1/8" chainrings, make sure you are not running the narrower 3/32" chain. (We also sell 3/32 chainwheels) If you need help choosing the tooth count, check our gearing calculator.