You may be confused about exactly how hard to work during cardio training. You may even think that high intensity exercise is the only way to go. After all, you can burn more calories and, even better, you don't have to spend as much time doing it.

But having some variety can help you stimulate all of your different energy systems, protect you from overuse injuries, and help you enjoy your workouts more.

High intensity cardio

For our purposes here, high intensity cardio falls between about 75 to 85 of your Maximum Heart Rate (MHR) or, if you're not using heart rate zones, about a six to eight on the perceived exertion scale.

What this translates to is exercise at a level that feels challenging and leaves you too breathless to talk much. But you're not going all out, as in sprinting as fast as you can.

There's no doubt that some high intensity training work can be helpful for weight loss as well as improving endurance and aerobic capacity. But, the number of calories you can burn isn't the whole story. If you do too many high intensity workouts every week, you risk overtraining, overuse injuries, burnout, inconsistent workouts, as well as boredom.

Not only that but, if you don't have much experience with exercise, you may not have the conditioning or the desire for breathless and challenging workouts. And if you have some kind of medical condition or injury, forget about doing high intensity training (or any kind of training) without checking with your doctor first.

If you're doing several days of cardio each week, which is what's recommended for weight loss, you would probably want just one or two workouts to fall into the high intensity range. You can use other workouts to target different areas of fitness (like endurance) and allow your body to recover.

Some examples of high intensity workouts:

A 20-minute workout at a fast pace

You can use any activity or machine, but the idea is to stay in the high intensity work zone throughout the workout. You'll find that 20 minutes is usually the recommended length for this kind of workout and most people wouldn't want to go much longer than that.

Interval training

A great way to incorporate high intensity training without doing it continuously is by doing intervals. Alternate a hard segment (e.g. run at a fast pace for 30 to 60 seconds) with a recovery segment (e.g. walking for one to two minutes). Repeat this series for the length of the workout, usually around 20 to 30 minutes.

Moderate intensity cardio

There are a variety of definitions of what moderate intensity exercise is, but it typically falls between about 60 to 70 of your maximum heart rate (a level four to six on this perceived exertion scale).

The lower end of this range usually incorporates the 'fat burning zone.' That means can carry on a conversation without much difficulty and you feel pretty comfortable with what you're doing.

Moderate intensity workouts have some great benefits such as:

• Comfort: Hard workouts are, well, hard. It takes time to build up the endurance and strength to handle challenging exercise. Moderate workouts allow you to work at a more comfortable pace, which means you may be more consistent with your program.
• Better health: Even modest movement can improve your fitness while lowering your risk of heart disease, diabetes and high blood pressure.
• More choices: High intensity workouts will usually involve some kind of impact or, at the least, a fast pace. But, you can usually get up into the more moderate heart rate zones with a variety of activities, providing you work hard enough.

For weight loss purposes, you would likely want the majority of your cardio workouts to fall into this range. Some examples:

Low intensity activity

Low intensity exercise is considered to be below about 50 to 55 of your MHR, or about a level three to five on this perceived exertion scale. This level of intensity is no doubt one of the more comfortable areas of exercise, keeping you at a pace that isn't too taxing and doesn't pose much of a challenge.

This, along with the idea that it burns more fat, makes this a popular place to stay. But, as we've learned, you can burn more calories if you work harder, and that's what you want for weight loss.

That doesn't mean that low intensity exercise has no purpose. It involves the kind of long, slow activities you feel like you could do all day and, even better, activities you usually enjoy such as:

This doesn't have to be a structured, scheduled workout, but something you do all day long by walking more, taking the stairs, doing more physical chores around the house, etc. For help in setting up a cardio program that includes a variety of different workouts, check out this sample cardio workout schedule.

Monday:
This should be a high intensity workout of about 20-30 minutes. Running and walking — alternate one-minute sprint with two minutes walking. Perceived Exertion for the sprints should be and eight or nine, while walking should be a five or six.

Tuesday:
Medium intensity today of about 45-60 minutes, walking or jogging. Exertion five or six.

Wednesday:
Today do low to medium intensity, all day long. Use a pedometer and try to get 10 000 steps.

Thursday:
Today's intensity should be medium to high for 30-60 minutes. Something like kickboxing at an exertion level of five to seven is ideal.

Friday:
Today use the elliptical trainer for a duration of 30-45 minutes at medium to high intensity at an exertion rate of 4-5.

Saturday:
Today's workout should be a walk or aerobics class at low-medium intensity for about 30 to 60 minutes at an exertion of four to six.