Cardiovascular fitness schedule

It has been proven conclusively that if you spend a few minutes every day exercising you will do your heart a whole lot of good. Even 20 minutes of exercise on at least 3-4 days in a week is more than enough to improve cardiovascular fitness, burn calories and tone up your body.
What are the various exercises one can do to improve the cardiac fitness?
1. Riding a stationary bike: Pedal with medium resistance and gradually increase the speed and resistance.
2. Walk on a treadmill: Take rapid and long strides and aim to attain a speed of 4.5 miles per hour. Ten minutes into the workout increase the incline.
3. Run on a treadmill: Begin with walking, after 3 minutes run for a minute and then again return to a slow run rhythm for 1 minutes followed by a one-minute run.
4. Power walks: Walk outside at ba brisk pace for 20 minutes choosing a medium incline route and try to walk at least a mile and a half in 20 minutes.
5. Interval runs: Run at a hard pace for 100 meters followed by a relaxed jog for 100 meters and keep alternating the cycles over the entire 20 minutes.
6. On rainy days exercise indoors. Run up and down the stairs five times. Do push-ups and crunches.
Always remember to do stretches everyday and before working-out. Start slowly and gently. Respect your body. Remember Rome was not built in a single day. Consult your doctor or fitness trainer before embarking on any fitness regime.