You may remember hurdler Michelle Jenneke's famous dance where she wiggles her fingers to warm up before the race. In this interview (at 01:11), she reveals that wiggling her fingers activates her fast twitch fibers. Is this scientifically valid? And if so, why do your legs become more explosive from movements in your fingers?
There's not really a correlation between twitching your fingers and power in your legs. Plus, you don't "activate" your fast twitch fibers. There isn't a switch that turns them on, and they are not independent. You would also be using the slow twitch fibers in the muscle as well. So physically speaking, the finger twitching isn't doing what she says/thinks it does.
What it does do, however, is act as a mental trigger. She has a pre race routine, with the hops, bends, leg and finger twitching, etc. What this does is get her in the mental state to race. You see this with all kinds of athletes in various sports, they all have different routines that basically tell their brain and body "Hey, it's time to race".