Aerobic fitness is often considered the cornerstone of a healthy lifestyle. Aerobics classes were borne out of dance an extremely fun alternative to the monotony of running or cycling. Aerobics comes in many forms and has evolved greatly in the past 10 years. This has made it much more effective in general and often safer and more understood than in the past. Most importantly, it has become much more fun.

Clearly, if you are looking to burn more calories and get more of a weight loss effect from an aerobics class, than you need to look at classes which involve the entire body - Tae Bo and step aerobics are two of the most popular.

Is your aerobics class too intense?

How do you know if your class is right for you? If the class is too intense, you will feel an excessive burn in the muscle groups you are working and your breathing will become increasingly more labored. This is due to the build up of lactic acid. In this case, the intensity of your aerobics class is too high. Your muscles will be unable to produce energy because of the levels of lactic acid in your blood. This is also referred to as your "aerobic threshold".

It is a good idea to know your fitness level before you start an aerobics class. This will tell you how much oxygen you are able to consume, and more importantly, at what aerobic intensity you should exercise. DaiseyPT.com's fitness level calculator can show you how to do that.

Building up your aerobics endurance

Low fit individuals will have a low aerobic threshold and high fit individuals will have a high aerobic threshold. High intensity and shorter training sessions will recruit what is called fast twitch muscle fibers. This will help to increase the lactic acid threshold. High intensity training will have more of an effect on your overall cardiovascular system.

In other words, rather than trying to make it through a 30 minute class, break it up into three 10 minute class intervals, only do it at a slightly higher intensity. This will help increase your tolerance to and ability to get rid of the lactic acid that builds up in your muscles. Obviously, you will have to use an aerobics video at home for a while, since aerobics instructors are not likely to stop and start the class just for you!

Scientific Aerobics

By starting a well-constructed aerobics program, you should experience positive changes in your fat burning capacity, respiration and oxygen transporting ability, muscle fibers, tendons, bones and ligaments, and the heart and circulatory system.

There is a threshold or minimum level you must work at to make changes in fitness level, and body composition. If you adjust your intensity (how fast/hard your aerobics program is), duration (how long you exercise for) and your frequency (how many days per week you exercise) you can work at the right threshold and get the most out of your aerobics program.

To find the right intensity for you, lets first determine your fitness level. This requires a test whereby you walk one mile and record a few things. Our fitness level calculator can help you determine what range you should be exercising in. Once you have found your fitness level, use our target heart rate calculator to find exactly what your heart rate should be while you are engaging in aerobics.

Let's say you are a 30 year old woman at a moderate fitness level. This would mean, according to our calculators above, that you should optimally try to keep your heart rate between 147 beats/minute and 167 beats/minute. That represents 70% to 85% of your age/gender predicted maximal heart rate. Simply ask the aerobics instructor if she or he thinks that their class is that level of intensity for someone who is in moderate shape.

To monitor your heart rate, you can use a heart rate monitor which constant reading of your pulse rate at the glance of a watch. If not, you can track it the old fashioned way by checking your pulse at regular intervals (every 2-3 minutes). If you do not know how to do that, click here to learn how.

You should repeat this fitness level test every so often to upgrade your fitness level. Re-test yourself when your workout becomes too easy.

The duration is simply the time it takes to perform the aerobic activity, the amount of calories burned or the distance traveled. Click here to learn roughly how many calories are burned in relation to duration with an aerobics class as well as other cardiovascular exercises.

Most studies have shown that you should perform your aerobic exercise for no less than 30 minutes and no more than 60 minutes at a time to improve fitness and for weight control. Greater than 90 minutes can have an adverse effect, as you have basically used up all of your energy stores at that point resulting in a breakdown of muscle tissue for energy use.

Heart Rate Calories Burned per Minute 100 4.64 110 5.57 115 6.03 120 6.50 125 6.96 130 7.43 135 7.89 140 8.35 145 8.81 150 9.28 155 9.74 160 10.20 165 10.65 170 11.10 175 11.55 180 12.00

You know your fitness level, you know how intense you should work out (your target heart rate range). Now you simply have to adjust your duration and frequency to burn however many calories you need to burn. Let's say you want to burn 250 calories. In our example the lower intensity range for heart rate was 147 beats/minute. Find that number on the chart in the left-hand column. If your heart rate is consistently near 146 beats/minute, you should be burning roughly 8.81 calories per minute. It would take approximately 28 minutes at that intensity to burn 250 calories. If you do this 4 times per week, that is 1000 calories per week you are burning with exercise. Remember to start recording your duration AFTER you have warmed up and once your heart rate is in its target range. When you are deciding how frequently you are going to work out, try to divide it evenly over the week as shown in the example.

It is more beneficial to exercise more frequently. Remember, you need to train at least three days a week to reap the benefits. Trying to burn all the calories of your weekly goal in one workout dangerous. Plus, with every day you train, you are keeping your metabolic rate elevated.

Step Aerobics

Step aerobics was first introduced in Atlanta by a injured aerobics instructor named Gin Miller. She started climbing her porch steps as a form of rehabilitation for a knee injury and realized that "stepping" was not only a low impact, non-irritating form of exercise for her knee but also provided a good cardiovascular workout. Ms. Miller then began introducing step aerobics into the health clubs at which she taught. Shortly afterwards Ms. Miller teamed up with Reebok and formed Step ReebokTM. The rest is fitness history.

Force platform studies have shown that step aerobics is a low impact activity yet has a high energy cost and produces a good cardiovascular workout. A comparison that is usually made equates an hour of step aerobics with the same energy expenditure as running seven miles yet with the impact of walking at a three mile a hour pace. A key factor that contributes to this low impact/high intensity situation is that one foot is in contact with the ground or bench at all times, compared to running when both feet can be off the ground. However, the participant can however increase the stressful loads on the feet and legs by raising the bench height, hopping on and off the bench, using hand weights or using improper technique. Many of the reported step aerobic injuries are caused by technique errors or using a bench height that is too high for the participant's leg size.

Common technique errors

• Poor foot placement on the bench. By not having the foot fully placed on the bench, the heel can extend over the edge of the bench. This allows the heel to drop below the top of the step bench and done repetitively the Achilles tendon may get over stretched causing an Achilles tendinitis.
  
  
• Bouncing or hopping up and down off the bench. This puts a greater force load on the feet and legs especially if the participant is jumping off the bench with hand weights instead of stepping down. Stress fractures, shin splints and forefoot injuries, such as metatarsalgia ( toe joint inflammation) and sesmoiditis ( inflammation of the two small bones below the first metatarsal- ball of the foot) can result.
  
  
• Excessively high bench. A bench that is too high for the participant's leg size also causes its fair share of problems. As the bench height increases, a greater force load is placed on the knee joint and patellar tendon in the step up position since the knee needs to flex more to accommodate the step height. A good rule of thumb is never to use a bench higher than what is required for the knee to flex 83°-90°. As the bench height increases the participant's foot lands farther away from the bench when stepping down and back.
  
  This requires a lot of flexibility in the toe joints. If the participant's foot has any structural deformities that cause limited toe joint motion such as bunions or hammertoes the likelihood of developing metatarsalgia or sesamoiditis is greater. An increase in bench height will increase the load on the leg and foot setting the stage for the development of stress fractures.
  
  At the first sign of knee, foot or leg pain during step aerobics try to lower the bench height: this will reduce the force load on the injured area. Also evaluate fitness shoes for wear; shoes should have good forefoot padding and not be too flexible.

REFERENCES:
1. Maybury MC, Waterfield J: An investigation into the relation between step height and ground reaction forces in step exercise: a pilot study. Br J Sports Med 1997 Jun;31(2):109-13.