Q: What is the difference between anaerobic and aerobic exercise? - Layperson

A: The term "anaerobic" means "without air" or "without oxygen." Anaerobic exercise uses muscles at high intensity and a high rate of work for a short period of time. Anaerobic exercise helps us increase our muscle strength and stay ready for quick bursts of speed. Think of short and fast when you think of anaerobic exercise.

As you first start to exercise no matter whether you are walking or running, your muscles immediately begin to use energy to allow them to work. For the first three minutes your muscles will burn glycogen, a special sugar which is stored in the muscles for a quick infusion of energy. Some glycogen is always stored within your muscle tissues. During this period fat is not burned. This process is called anaerobic metabolism. Often during the first few minutes of strenuous activity, especially during anaerobic metabolism, you may experience burning in muscles of your arms, legs or back. This is due to the creation of lactic acid which occurs when glycogen is burned. In the following aerobic phase, a more slowly available oxygen supply is required, enabling the lactic acid to be broken down to carbon dioxide and water, releasing larger amounts of energy and the burning sensation will soon go away. 

The anaerobic threshold (AT) is the exercise intensity at which lactate (lactic acid) starts to accumulate in the blood stream. This happens when it is produced faster than it can be metabolized. This point is sometimes refered to as the lactic threshold, or the onset of blood lactate accumulation (OBLA). When exercising below the AT intensity any lactate produced by the muscles is removed by the body without it building up.

The anaerobic threshold is a useful measure for deciding exercise intensity for training and racing in endurance sports (eg running, cycling, rowing, swimming and cross country skiing).

Accurately measuing the anaerobic threshold involves taking blood samples (normally a pinprick to the thumb) during a ramp test where the exercise intensity is progressively increased.

Although the anaerobic threshold is defined as the point when lactic acid starts to accumulate, some testers approximate this by using the point at which lactate reaches a concentration of 4 mM (at rest it is around 1 mM).

A person's anaerobic threshold can be improved by exercising, and can vary between different sports. By definition a person's anaerobic threshold will never exceed a their VO2max - the point at which their body cannot supply any more oxygen to the muscles.VO₂ max is defined as the maximum volume of oxygen that a person can metabolise during exercise. (The derivation is V - volume, O₂ - oxygen, max - maximum.) It is expressed either as an absolute rate in litres per minute (l/min) or as a relative rate in millilitres per kilogram of bodyweight per minute (ml/kg/min).

Accurately measuring VO₂ max involves a ramp test in which exercise intensity is progressively increased while measuring the volume and oxygen concenration of the exhaled air.

Dr. Kenneth H. Cooper conducted a study for the United States Air Force in the late 1960s. One of the results of this was the Cooper test in which the distance covered running in 12 minutes is measured. An approximate estimate for VO₂ max is:

VO₂ max = (distance (in metres) covered in 12 minutes - 505)/45

 The relation between the two is reliant on the amount of training - an untrained individual reaches their AT at approximately 55%-60% of their VO₂ max, whereas elite endurance athletes reach their ATs at about 80-90% of VO₂.

As you exercise more than three minutes you will eventually burn up all of the glycogen stored within the muscles and your muscles will move into aerobic metabolism. When this occurs lactic acid production is stopped. This occurs because the glycogen is now being burned in the presence of oxygen which is brought to the muscles by way of the blood stream. As long as you breath correctly you will bring oxygen to the muscles and this process will continue.

Examples of anaerobic exercise include heavy weight lifting, sprinting, or any rapid burst of hard exercise. These anaerobic exercises cannot last long because oxygen is not used for energy and a by-product, called lactic acid, is produced.

Lactic Acid contributes to muscle fatigue and must be burned up by the body during a recovery period before another anaerobic bout of exercise can be attempted. The recovery period also allows the muscles to use oxygen to replenish the energy used during the high intensity exercise.

Aerobic exercise, on the other hand, includes lower intensity activities performed for longer periods of time. Activities like walking, jogging, swimming, and cycling require a great deal of oxygen to make the energy needed for prolonged exercise.

Oxygen is essential to the muscle's ability to function correctly. With adequate oxygen the muscles can extract all the energy they need from blood sugar. During the period you exercise the liver and muscles will release their stored carbohydrate so that it can be used as energy by the muscles hence allowing you to keep on exercising.

Once these stores of glycogen are used up which usually occurs after about 20 minutes, the body will start burning its fat stores to produce blood sugar and ultimately glycogen. The longer you exercise the more fat burned. Fat, body fat and not dietary fat, can now be used virtually indefinitely to produce energy to support your exercise program.

Anaerobic exercise burns more calories than aerobic exercise because each movement generates more force from the cells. However when muscle cells contract with more force they switch to using carbohydrates as the main energy source. This type of exercise may seem incorrect for weight loss but in fact it helps produce an adaptive response with a side effect of an increased metabolic rate. During periods of rest the cells accelerate the fat burning process.

Aerobic exercise can develop into anaerobic exercise

Most exercises can be performed as aerobic (burn fat) or anaerobic (burn mainly carbohydrates) the terms simply refer to the energy pathway required. For example walking is easy and a good aerobic exercise but if we increase the effort the body moves faster, eventually we end up running which then uses the anaerobic energy pathway. The Anaerobic pathway means oxygen uptake becomes insufficient for fat to continue to be the main fuel source.

In fact most exercises or movements we perform result in a split between the fuels used, for example if the effort is about average like vacuuming a room or washing a car then we'll probably be burning about 50% carbohydrates and 50% fat.

Fast weight loss will come when the individual performs each exercise correctly and within their own unique capacity.

To change this rule you must burn stored fat indirectly by using anaerobic exercises to increase your metabolic rate.

While you are walking, you do not directly burn fat but once you stop walking the glycogen which has been burned up must be replaced. This can only happen by what you eat and by the liver draws fat from the body's fat tissues. If you are on a limited caloric intake then the food you ingest will be used basically for feeding your brain and fat stores will have to be drawn on to replace the glycogen used up while exercising.

Studies show that "fat-burning" may last for anywhere from six to twenty-four hours after a regular exercise program. This means that even moderate exercise has long term benefits for you.

Studies, however, also show us that the percentage of energy contributed from burning fat decreases as you increase the intensity of your exercise program. This means that you do not have to exercise intensely or exert great effort but rather than only mild to moderate exercise on a regular basis is needed.

What I suggested above is that you must exercise for at least 20 minutes each and every time you exercise. In the beginning less is acceptable. But gradually as you will become more conditioned to setting time aside, making exercise a part of your life and then you can increase your exercise time to a minimum of 20 minutes three to four times a week.

As you get more into the swing of things, you can either increase the frequency of your exercise program or increase the length of time you put aside for your exercise program. It is often wise to vary the exercises you use. For example, you can walk one day, play golf or tennis on another day and then alternate a different exercise, such as stationary cycling, cross country skiing and rowing to the list of exercises from which you chose, each day or every few days.

Eventually work up to 30 to 60 minutes of aerobic exercise each time you exercise. Remember, it is essential to start slowly and build stamina steadily until you reach this time range.

It is also essential work hard enough to reach you heart target range.

Exercise is most valuable from a cardiovascular point of view when the heart is not over taxed but yet is challenged. The best way to do this is to bring the rate that our heart beats (pulse measured in the lower extremities) into a range which is between 60% and 85% of the maximum heart rate. The maximum heart rate refers to that approximate level after which there is real or potential danger to the individual and where the heart is over taxed. At this rate exercise is difficult and will cause fatigue within minutes or sooner. Below this and within the Target Range the heart is strengthened and made healthier. The target heart range is a calculated figure which depends on age. The ability to reach and maintain a heart beat within the target range depends on the health of the heart, conditioning, frequency of exercise and the length of time exercising.

It is essential that each individual about to embark on using a regular, strenuous exercise program should have a complete physical examination. If there is indication of heart disease or dysrhythmia an electrocardiogram should also be done.

Calculating the Target Heart Range:

1. The first thing you do is to subtract your age from 220 to get your maximum heart rate.

2. Multiply your maximum heart rate first by .60 (60%) and then by .85 (85%). This will give you your target heart range.

Suppose you are 25 years of age the calculations would look like the following:

Now you calculate your own target heart range:

Note: There is one exception to this rule. That is men and women who are taking a specific group of medications called beta blockers. These medications (Betapace, Blocadren, Breviblock, Cantrol, Keroline, Inderal, Inderide, Levatol, Lopressor, Tenoretic, Tenormin, Timolide, Spectral, Topal XL, Viskin and Ziac) control the heart rate and therefore they will not allow the heart to reach the target range. Often what happens with individuals on beta blockers is that they will become fatigues long before they can get their heart rate into the target range, assuming they even can.

In order to be sure that you are in your target heart range, you must take your pulse periodically. This is not always necessary, especially if you really don not care whether you reach your target heart range or not. However, if you do want to check your pulse, it is easiest taken during exercise in the area of the Carotid artery. If both hand are free you can take a peripheral pulse in one or the other of the writs.

To take your pulse using the Carotid artery first find your Adam's Apple. It is best to do this first when you are not exercising. Touch the Adam's Apple with your thumb and then reach the first two fingers toward the side of the neck. You will feel a group of muscles running vertically from the base of the head down toward the notch of the color bone. You will find the carotid pulse just in front of this group of muscles approximately four finger breadths from the Adam's Apple.

It is best felt using the index and middle fingers. Do not use your thumb as you may feel its pulse and confuse you. Never push hard. Only a light touch is ever necessary to feel the carotid pulse. Pushing too hard can constrict the carotid artery and cause lightheadedness or even damage to the artery.

Once you locate your pulse you can either count for ten seconds and then multiply by six or count for fifteen seconds and multiply by four. Both of these methods will give your heart beats per minute.

To determine if you are in the target heart range take your pulse both half way through your exercise program and then again when you complete it. You can also take your pulse at any point during your exercise program, especially if you feel fatigued. If your heart rate seems irregular or you suspect you have already surpassed your maximum rate, slow down and back off until your heart rate becomes regular and returns to the Target Heart Range.

It should be clear from what we have said above that correct breathing is essential for the optimal results. This is often ignored but it should not be. It is essential that you never stop breathing, hold your breath or get out of breath while exercising. When this happens, your body will go into oxygen debt and this means that you will reduce the amount of fat you will later burn when your program is complete.

Since breathing is essential, we recommend that you learn to breathe regularly and easily as you exercise and that you never exercise so hard that you run out of breath. Generally, it is best to breathe in before exertion and breath out with exertion. Often this is hard to do unless you have good couching to keep you on track. For this reason it is often valuable to exercise in a group or under supervision until you master your breathing. Learning it right the first time is always the best idea.

Benefits of Regular Exercise

1. Exercise builds muscle mass. Larger muscles burn more calories than smaller muscles. This means that more fat will be burned to maintain your muscles on our program. It also means that you can eat more without gaining weight.

2. Moderate exercise can decrease your appetite. Studies have shown us that light exercise increases appetite while heavy exercise decrease appetite initially but within a short time appetite will increase. Moderate activity, on the other hand, lowers appetite and decreases your desire to eat.

3. Exercise helps to reduce stress and depression both of which are common causes of overeating. While exercising, non-threatening and non-stressfully, endorphins are released which make you fell better. These natural chemicals diminish depression and relieve stress.

4. Exercise reduces your risk of heart disease. This is benefited when the individual eats a low fat, high complex carbohydrate diet high in magnesium.

5. It reduces blood pressure. This is benefited when the individual eats a low fat, high complex carbohydrate diet high in fiber and in magnesium.

6. It increases HDL-Cholesterol (the good cholesterol fraction) and diminishes LDL-Cholesterol (the bad cholesterol fraction). This is benefited when the individual eats a low fat, high complex carbohydrate diet high in magnesium.

7. Reduces the risk of diabetes by increasing the use of sugar in a healthy and productive way. It also helps because weight is lost and muscle mass is increased. Its benefits are most pronounced when associated with healthy eating and vitamin-mineral supplements.

8. Strengthen the heart muscle. As we exercise regularly, the heart muscle becomes stronger hence it pumps better and more blood is pumped with each beat of the heart muscle. This means the heart does not have to work so hard and hence becomes healthier.

9. Regular exercise will decrease your risk of osteoporosis in women. Exercise strengthens bones making them less likely to break.

10. Exercise can help you sleep better.

11. Regular exercise helps to keep the bowels operating on a regular basis.

12. It also helps to improve circulation and function of weight bearing joints.

13. It can help us to feel fit and it improves the function of the immune system. Therefore, regular exercise can help to decrease the risk of many different illnesses.

14. You not only feel better but look better hence stimulating self-image and self-esteem.

You will always by protecting yourself, your heart and your well-being if you warm up prior to strenuous exercise and cool off after prolonged exercise. This is essential. Warming up prepares the muscles for strenuous exercise. It decreases the chance of Charlie horses, muscle strains and injuries. It also prepares the heart to build slowly to be ready for the work out you are about to give it. Proper cool down will prevent soreness, cramping as well as getting the blood back to your heart after exercise. This can prevent dizziness and lightheadedness.

Generally, one should warm up and cool down for five to ten minutes before and after strenuous exercise. It can be considered to be part of the exercise. For example, if you are bicycling, ride at a reasonable pace without pushing it for the first five minutes than gradually increase your speed until you have reached you Target Heart Rate after you reached the end of your exercise program reduce your speed to about the same level of the warm up. This is best done as gradual winding down until the five to ten minutes are up and then the exercise can be terminated. The same thing applies to walking, running, jogging and tennis.