It only rises if you still have his second jump.
Actually, I think it also rises if you use it while rising during his second jump as well, but I know if you've already used up your second jump it does nothing but hinder your recovery instead of help it.
My Creations in Modnation Racers! Check zhem!
http://community.modnation.com/en-us/players/IvoYaridovich/creations