Can you get fit in six minutes per week is good for mice but will it work with men and women?
I think it may be safe to say that you can get a quick workout burning the same number of calories in a much longer and slower workout. I have had some personal experience in this regard and have also seen others excel in athletics with less effort.
When my schedule got too busy many years ago, for two full years, I dropped from the daily 5-mile run at a 7-minute/mile pace to a two mile sprint at a 5:30 minute/mile pace. In those two years of short runs I fell fitter just with one-fifth of my previous running load. I can also swim for one hour or sprint short laps for 20 minutes and could be equally burnt out. However, when it comes to bicycling I frequently rotate with sprints and do slower long rides to absorb the beauty of the country side.
Age is also a factor. If you are young, then frequent sprinting may work for you. Older folks may like to just do any activity at a comfortable pace. If age is X and Y is pace, as X increases, Y decreases. When Y reaches zero, X has reached its limit. Therefore, adjust your workouts with age and fittness levels.
From the above report (link above) you will note that in impact sports (running for example) too much of the sprint or quick workout may lead to knee and ankle injuries. However, with non-impact sports like swimming and bicycling, you can engage sprint workouts more frequently than in running. Jobless runners have posted faster times in the 2009 Boston marathon because they had more time to train. However, if they continue to train and run at that same pace, they'll be slowed down with injuries and stiff limbs. What you can do with bicycling and swimming you cannot do with running.
Is less equal to more? I have met many a marathon runner who would train not more than four times a week and have better marathon performance that others who trained 7 days a week. I have not run in a decade now but have kept as fit by bicycling, swimming and walking. Humans were meant to be upright (walk), therefore walking is a great exercise and you can engage it as "brisk" or as "slow" as you want it.