Tonights Session - Intervals.
Interval training is designed to maximise your aerobic power. How much blood can you deliver to the running muscles, and how much of that oxygen that's delivered can convert fuel into energy.
Intervals are done at about 97 to 100% of your max heart rate.
Intervals are "hard" but not all-out running by any means. Usually at a pace that you could maintain for about 10-15 minutes in a serious race.
Intervals are best if they involve runs of 3 to 5 minutes each (800m and 1000m workouts are typical), with jog recoveries of similar duration (not necessarily, equal distance); relative to the runs they follow.
Purpose: Stress your aerobic power (VO2max). It takes about two minutes for you to gear up to functioning at VO2max so the ideal duration of an "Interval" is 3-5 minutes each. The reason not to go past 5-minutes is to prevent anaerobic involvement, which can result in blood-lactate build-up.
There is a great video here by Jack Daniels on Intervals.
Tonights set is:
After warm-ups etc.
Repeat 5 times
Interval 1.00 km
Recovery Jog 2 min