Just as Quik said. So if you wanted to increase only density on week one you would do 10 x 100m in 12 seconds with 3 minutes rest; week two would be the same workout with 2:30 rest; and week 3 would be with 2 minutes rest. Sometimes I'll use similar setups in the weight room during GPP or for hybrid race modeling / speed endurance work later in the year but you have to watch carefully because if the reduction in rest exceeds the level of adaptation you will greatly increase the relative intensity of the workout…something which could be problematic.
ELITETRACK Founder