Two recent additions to my dryland routine are stretch cords and plyos:
Seem to act differently than weights, and there's a bonus with freedom to try plenty of movements. Also works stability groups in joints. The type of muscle fibers required I haven't figured out, but like gravity resistance, it's probably related to load and the speed of the movement. Anyhow, it feels different than moving mass around, and provides a nice alternative or compliment to weights. Sometimes I add a few cords in various places of weight machines (and free weights) in addition to the weight for an added effect near the end of the movement. Plyometrics
Depth Jumps: Hopping from a 10 - 30" platform and rebounding with a jump within a fraction of a second from landing. The land loads the muscles and tendons, which is the preload for the jump. I find a location with a series of platforms at various heights (bleachers) and use static objects forward of view to gauge jump height, like a baseball field fence about 20' away and a building much further back. I place a mark on the fence at achieved peak heights. The goal is to start from a low platform and gradually increase the depth of jump in relation to achieved vertical increases. People usually stare at the strange exercise. If asked, I tell them I'm catching insects.
This helps my race starts, which is most of the race in a 50
I also made up the plyometric pushup: It's just a old school "girls pushup" (aft supported from the knees instead of feet), but start by kneeling upright. While keeping things straight, you land and quickly bounce, with a push, back to vertical. Seems to work better with a tethered stretch cord pulling you back up. This exercise is done at home for obvious reasons.
Hoping this will help upper body speed.