The Rise of the Minimalist Workout - NYTimes.com: " . . .The most recent research suggests that a few minutes per week of strenuous exercise can improve aerobic fitness, generally more quickly than moderate activity does.
In a representative study, which I wrote about this week, Norwegian scientists found that three four-minute runs a week — at a pace equivalent to 90 percent of a person’s maximal heart rate, an intensity that will feel, frankly, unpleasant — improved volunteers’ endurance capacity by about 10 percent after 10 weeks. . . ." (read more at link above)