Length Vs. Intensity Cardio

The benefits of cardiovascular exercise include improved heart health, body weight, stamina and energy, as well as a lower incidence of disease. For the most part, the benefits you reap from your cardiovascular exercise routine are determined by the amount of total work that you do. So a long workout done at low intensity is roughly comparable to a short workout done at high intensity. However, there are some differences in the benefits of both.

Intensity

Intensity comparisons often bring on complicated discussions of heart rate training zones and VO2 max, but the easiest field test is checking how hard you are breathing. The talk test is an easy way to gauge intensity. Your aerobic exercise is in the low range -- 50 to 60 percent of maximum -- if you are able to carry on a conversation that sounds natural while you exercise. The target zone for most exercisers -- 60 to 80 percent of maximum -- will leave you able to say only about three words in between breaths. You won't be gasping for breath, but the conversation will be noticeably interrupted by your need to inhale. High-intensity training will not allow you to carry on a conversation at all. At most, you'll be able to get out a word or two, but you won't want to talk because you need every breath you can get to keep going. This level of intensity can be sustained over relatively short periods of time only.

Long and Slow

When your goal is to build endurance, the long and slow workout is a staple. Runners building up to a long race add a long slow run to each training week as a tool for gradually increasing mileage. Adding distance before increasing speed is also a useful tool for relatively new or deconditioned exercisers because it allows them to burn more calories and make fitness gains with a much lower risk of heart attack or other injury.

Short and Fast

There are some benefits of doing harder work for a shorter period of time. Higher-intensity cardiovascular exercise puts more stress on the heart muscle, which in a healthy individual will lead to strength gains in the heart and result in a lower resting heart rate. A 2002 study in "Sports Medicine" reported that gains in peak performance for highly trained endurance athletes could only be achieved through high-intensity training. The study supported evidence that you may eventually come to a point where you will stop seeing improvement by increasing the length or your aerobic routine and need to incorporate high-intensity training for further benefits.

Using Both

You should always consult a doctor before beginning a new exercise program to make sure that you are healthy enough to proceed. Those new to exercising should spend at least three to four weeks building length onto a relatively low-intensity cardiovascular workout routine. After building a foundation in low-intensity cardio and adding some higher-intensity work, you can reap the maximum benefits by incorporating both types of cardio into your training schedule.

Suggestions

If you currently exercise three times per week doing 45 minutes of low-intensity cardio, make changes in your routine to incorporate higher-intensity work into your training schedule. Keep two of the three workouts the same, but change the third to an interval session by adding five to 10 short segments of harder work that lasts between 20 to 90 seconds. Add a fourth workout session that is shorter -- only 20 to 25 minutes -- and consider that to be your "intense" workout. Do a five-minute warmup, then ramp up either speed or resistance to increase the intensity beyond your comfort level. A 10 percent increase in difficulty is a good goal. Include at least a five-minute cool down at the end to ensure that your heart rate decreases slowly to avoid unnecessary strain on the heart.

Try something new. Adding a new activity uses your muscles in an unfamiliar way, and the lack of proficiency tends to cause you to work harder naturally. As an added bonus, you'll learn new activities to keep you interested in fitness and stave off boredom.