I believe you what you're looking for is how to improve your fast twitch muscle fibers.
Fast-twitch fibers allow one to generate a relatively high amount of
force in a short period. The take-off motion in a sprint and long jump
(when the foot is in contact with the ground for a millisecond) are
perfect examples of this.
as opposed to:
Slow-twitch fibers, on the other hand, come into play during the pure
endurance aspect of these events. Fatigue resistance, at the expense
of fast rate force production, is the hallmark of these fibers.
You had the right idea with high-intensity exercises, they develop the fast twitch fibers while low-intensity endurance exercises develop the slow twitch fibers.
Here are some tips from an eHow article:
Perform sets of short sprints twice a week in addition to your
regular workout routine. Maximum effort sprints over distances
between 20 and 50 meters give your fast twitch muscle fibers a
Add one or two session of longer sprints to your weekly workout.
Going all-out for more than 50 meters is extremely tiring, so run
these sprints at around 85 percent effort for the best results.
Focus on quickness and fluidity of motion.
Make time for weight training. Research studies show a direct link
between maximum strength and overall speed, so using heavy weights
to make yourself stronger will beef up your fast twitch fibers.
You could also try isometric muscle training, defined as:
Isometrics, as it pertains to muscle training, involves tensing
muscles against other muscles or against an immovable object while the
length of the muscle remains unchanged. For isometric training to be
effective, this muscular tension must be maintained over a certain
period of time.