Tabatas are AMAZING for fitness training! Each exercise is only 4 minutes long, but you work at maximum effort. You'll blast calories, increase both your aerobic and anaerobic capacity, and increase your strength as well!
I usually include Tabatas into my routine once a week, combining 6-7 Tabatas with an ab routine and a 1-minute cardio interval.
How do you do them? You set an interval timer (I use the free Gymboss app on my phone) for 4-8 rounds of 20 sec work and 10 sec rest.
You perform Exercise #1 for 20 seconds, then rest for 10 seconds, then do that same exercise for 20 seconds, rest for 10 seconds, etc., until you have completed all 8 rounds (or 4 or 6).
Beginners: 4 rounds
Intermediate: 6 rounds
Advanced: 8 rounds