measure 15 meters in open area . Mark the distance with masking tape. also, measure and place masking tape at meters
walk 15 meters in such a way that you keep moving faster throughout the entire distance
have 2 people time you . one person time you for the first 5 meters and other person time you for the last 5 meters
Repeat step 2 , walking the 15 meters in less time than you did before (faster) . then try it again, this time walking the distance in twice the time as the first (slower) . remember to keep speeding up throughout the entire 15 meters