Given a question and a context passage, generate the answer having the word or phrase from the context passage. Here, the answer should be a shortest continous span from the passage.

Context: I had about 10 minutes to exercise before I had to pick up my two older daughters from school yesterday. It was a busier day than usual for me with a couple of meetings besides my regular work. Years ago, I would have put off my workout and would have left things for the next day. But since it was a busy day as well, I knew that I may not have all that much time either. So, I picked up my kettle-bell and _ for 4 minutes. See, 4 minutes, if that's all you've got, is enough to give your body a great fat-burning exercise. How did I get a killer workout in 4 minutes? I used a training workout discovered 10 years ago by a Japanese Sports Scientist called a TABATA. It includes 20-second periods of warm-up, followed by 10-second periods of rest and 4-minute straight exercise. How is a 4-minute exercise able to burn fat? It all depends on the quality of work you do. Not on the quantity. Here's how I did it yesterday. You should never forget your warm-up. A TABATA workout is 20 seconds of 2-arm Kettle-bell swings, 10 seconds rest, 20 seconds push-ups, and 10 seconds rest. You should do those 4 rounds. That's it. I was done in a total time of 8 minutes by the time and when I got to school my heart was still pumping pretty hard. A healthy body is needed for studying and working, and efficiency is the key to building a great body in the least amount of time possible and you can't get more efficient than a 4-minute workout.
Question: What is the most important thing in taking exercise according to the author?
the quality