Interval training workouts have shown to be the most effective cardiovascular training method for improving cardiovascular endurance, sport- specific performance, boosting metabolic rate and burning fat!
INTERVAL WORKOUT 1:
Interval training protocol: 10 sec @ 100%: 30 sec @ 60% x 18 = 12 minutes
This running workout is probably easier to do outside instead of on the treadmill. The reason - most treadmills take too much time to adjust to the speed you choose. Do this one outside and simply sprint, jog, sprint. It's as easy as that.
INTERVAL WORKOUT 2:
Interval training protocol: 1min @ 100% : 2 min recovery = Repeat for 20 minutes
INTERVAL WORKOUT 3:
Interval training protocol: 100 meter hill sprint, walk down hill and fully recover = Repeat for 20 minutes, this one is good if you have bad knees as it takes away the impact from your knees.