Cardiovascular (or aerobic) exercise might seem like an easy thing to pick up and do. For many it is, but others have questions: what kind of exercise should I do, how far should I run? For those, the ACSM (American College of Sports Medicine) provides a few guidelines.
Mode of Exercise
Your intensity level will determine how many times per week you should engage in cardiovascular workouts. The ACSM recommends 3-5 days per week for the general population. Three days a week will work if you intensity is above 77% of your max heart rate.
If you are working out at a lower intensity, consider exercising 4 or 5 days per week. Six or more days a week is not recommended since generally only professional athletes can see significant improvements.
Next you need to figure out what intensity you'll be working out at. The is usually done relative to your maximum heart rate. The ACSM recommends your intensity be anywhere from 64% to 94% of your max heart rate. Beginners can improve their fitness levels even at low intensities and work upwards. If you are in shape you can workout at a higher intensity.
Your workouts should last a minimum of 20 minutes (not including your warm up and cool down phases) but no more than 60 minutes. For most people up to 30 minutes is enough.
You can also break it up into more than one session throughout the day. For example, you can bike ride for 10 minutes at a time but do 2 or 3 bike rides in a day. The higher your intensity, the shorter your workout can be.
The Bottom Line
All these rules aren't made to make it difficult or scare you away from an activity. Following these guidelines will make your workouts safer and more effective. Sticking by them will improve your health and performance in the long run but the most important thing is that you get out there, exercise and have fun.