i preload against the brake then carry on pushing through the pedals once i've released the brake
i'll give it a go ,its where you apply force to something before you attempt something ,lol thats the best i can do .
if you watch a vid of say damon watson ,watch his rear tire before he hops /gaps ,he "preloads" his rear tire (you can see it squash down ) ,this gives him extra bounce .
sorry for the crap explaination,i tried ,im sure someone who can explain better will post later.
steve