Tabatta This…

Here is the explanation from the FAQ on Crossfit.com:

Tabata Intervals ( 20 seconds of work followed by 10 seconds of rest repeated 8 times) is applied in turn to the Squat, Rower, Pullups, Sit-ups, and Push-ups with a one minute rotation break between exercises. Each exercise is scored by the weakest number of reps (calories on the rower) in each of the eight intervals. During the one minute rotation time allowed the clock is not stopped but kept running. The score is the total of the scores from the five stations.

Some performance insights and a scoring example from Mark Twight:

1. Lying down between exercises lowers HR faster than standing, sitting or walking, indicating better recovery in the short 60 second rest.
2. Alternating upright exercise (squat, pull-up) with prone or seated exercises produces lower heart rates, and allows greater overall level of work
3. Rowing first reduces reps on all other exercises
4. Rowing reps are not seriously affected if done last
5. Improvement happens really fast when the workout is done consistently (bimonthly).
6. High number of reps may be maintained for greater number of sets as fitness improves. Rep totals do not necessarily improve per set, but now I can do 6 sets of 7 pull-ups rather than doing 11, 8, 5, 4, 4, 4, 4, 4, etc. which suggests that local area endurance and lactic acid tolerance improve with this protocol.

Scoring Example:
A total score of 53 (Execllent score, BTW) is determined by adding up the lowest number of reps in any set of each exercise.
18 squats
4 pull-up
6 push-up
13 sit-up
12 row (use the calorie counter and call each calorie a rep)
This score is a 53.