Four minutes. To good to be true? The whole workout might take a bit longer than four minutes, but it only requires 3 to 4 minutes of actual hard work made up of 6-8 x 30 second sprints. I love this workout for two reasons: First, you can do ANYTHING for thirty seconds: about the time the effort starts to get really uncomfortable, you're done. Second, even though the work portion of this workout is short, the body experiences a training stress equivalent to a significantly lo