A research study conducted at the University of Texas concluded that four seconds of intense intervals, repeated until they amount to a minute of total exertion, led to rapid improvements in strength and fitness in middle-aged and older adults. This New York Times article (subscription may be required) also links to the full study.
What is important to note about research like this is that it is making it harder to make excuses for not exercising! Get up and move throughout the day.
