My days are so jam packed I have to really ROCK OUT my exercise timeframe. In 20 minutes I can do that with interval training. On my treadmill I perform 4 five minute intervals. I start on my highest incline speed at 3 to 4 mph for 2 minutes. I lower incline to 1 and jog for 2 minutes at speed of
4.5 to 6.5. I ramp up to incline of 3.5 and do a comfortable walk speed for 1 minute. Then I repeat the entire circuit for 3 more times bringing me to my 20 minutes of interval exercise.
Every other day I push my speed on the uphill portion and the flat run. My goal is speed not time. It works