Fibers are recruited according to amount of resistance, not on speed of movement? Please take the time to educate yourself before making absurd statements. Reference Digby Sale or any P.V Komi research if you can lend yourself from the elitefts website for a while.
If fibers are recruited according to amount of resistance, then is body weight enough resistance to recruit type IIX fibers? If not then sprinters must not recruit these fibers while sprinting since it depends on amount of resistance.
To improve power you must train across a loading spectrum. That is why Olympic lifter do lifts at lower percentages and move the weight faster, even the Snatch movement is essentially training at a lighter load. Pulls are some times loaded even more so than their max. They will do lighter days and work on speed of movement as well. Again the olympic lifts are always tried to be moved fast as possible, thus recruiting higher treshold MU, again see the research. Most Olympic lifters DO jumps and other jumps, IE the Chinese. If triple jumper only bonds and leaps he can make improvements but only to certain point to where other factors that allow him to express his jumping ability come into play like his strength and power levels. Improve his strength-speed abilities and you may continue to see improvements.