There is no valid reason that a healthy person should maintain a low intensity exercise regimen unless they simply aren't really interested in seeing real results. A low intensity workout, defined as exercises during which your heart rate is around 60% of its maximum rate, are fairly inefficient for anything other than very slow and gradual weight loss. They won't help you boost your metabolism, they won't aid significantly in building muscle mass, and they don't do much for strength and endurance.

A high intensity workout, which is defined as exercises which push your heart rate up to 75% of its maximum or more, is infinitely better for nearly every aspect of your overall health.

You can determine your maximum heart rate by taking your current age away from 220. So, for example, if you're 50 at the moment, then your maximum heart rate is 170 beats per minute. Don't let the term "maximum heart rate" fool or scare you. You aren't going to damage your heart if you go up to or over this heart rate.

The 220-age formula is only an estimate and, depending on your individual physiology, you may find yourself exceeding that number. Since it's nearly impossible to damage a healthy heart by exercise, that's nothing to worry about.

Low intensity exercises are beneficial for warming up and cooling down, before and after high intensity phases. Low intensity exercises are also good for the elderly, anyone recovering from an illness or injury, someone who is significantly overweight and out of shape, or someone who is just beginning to workout.

Sadly, a good number of healthy people who could be receiving major benefits from high intensity workouts are stuck doing inferior low intensity exercises because a personal trainer has recommended it. Generally, a trainer would recommend the less effective low intensity exercises for one of two reasons: confusion or personal protection.

Personal protection simply means that a person is very unlikely to injure themselves during a low intensity workout so a trainer who is particularly paranoid about lawsuits may recommend the safer route. Most trainers who would do this are either entirely unsure of their abilities, planning to be absent for their clients workout period, or simply unfit to be a trainer.

The confusion route is more common and more difficult to explain. Both intensity levels burn calories and, of those calories, a percentage of them are fat calories. Technically speaking, a low intensity workout burns a higher percentage (50%) of fat calories than a high intensity workout (40%). Because of this, some trainers will recommend the workout wherein 50% of the burned calories are fat.

Sadly, this doesn't actually result in the client burning more fat and, thus, the confusion.

A high intensity workout burns a higher number or calories overall than a low intensity workout. Generally speaking, a smaller percentage of a larger number is often times more than a higher percentage of a smaller number.

Let us suppose that you burn 100 calories by walking for 20 minutes. Walking is a low intensity exercise, so 50% of those calories are fat, meaning that your 20 minutes of work has succeeded in burning 50 fat calories. Let us also suppose that you burn 160 calories during 10 minutes of a high intensity exercise. Of those 160 calories, 40% of the burned calories are fat which means that your 10 minutes of work burned 64 calories.

Despite the smaller percentage, in our example you burn 14 more fat calories in half the time. Now, half the time doesn't mean half the work because those 10 minutes are at a higher intensity. However, half the time is still half the time.

If you're really serious about losing weight, make the bulk of your exercise regimen high intensity and bookend it with warm up and cool down low intensity exercises.