What Everybody Ought to Know About the Benefits of being fit if You Have Diabetes: Effects of Exercise on Blood Glucose Levels

Written by Sue Rollins

Did you know that you can more easily manage your diabetes just by engaging in regular exercise?  Exercise generally has a very beneficial effect on blood  glucose levels in people with type 2 diabetes. When you engage in exercise, you expend a lot of energy.  This first comes from the glucose stored in your liver and your muscles.  At first, the body simply uses up the stored glucose (in the form of glycogen).   Thus, engaging in exercise does not mean your blood glucose levels will necessarily fall to dangerously low levels.   The situation is somewhat different in people with type 1 diabetes and in people with type 2 diabetes who take medications that can cause hypoglycemia.  Often these people need to take snacks at regular intervals during exercise to avoid hypoglycemia.  The body is very clever and has a number of mechanisms to prevent the blood glucose level from falling too low.  For example, with exercise and also if the blood glucose level drops below normal, glucagon, a hormone stored in the pancreas gets released.  This hormone promotes further release of glucose stored in the liver.  The same is true of the hormone epinephrine, stored in the adrenal cortex.  If one does enough exercise to use up most of the stored glucose, the body can make “new” glucose from the breakdown of proteins.  Also, breakdown of fats will occur, providing an alternative source of  energy, thereby “sparing” glucose stores.  In addition, regular exercise actually increases a person’s insulin sensitivity, making the insulin they produce (or take), more effective in controlling blood glucose levels.

Why is the effect of exercise on glucose levels important to those with type 2 diabetes?

Exercise indeed has a good effect on a patient’s glucose level. This is good news for people who have type 2 diabetes. A lot of research indicates that patients of diabetes gain more control over their diabetes as soon as they get into to a regular exercise program.  Since exercise improves your insulin sensitivity, you may need less medication in order to control the diabetes.

Should patients with type 2 diabetes exercise more often or differently than otherwise healthy people?

Experts recommend that people who have type 2 diabetes should exercise about 30-60 minutes (usually only moderate aerobic activity) at least 3 days a week.   Any amount of exercise is better than no exercise.

What type of exercise is best for patients with type 2 diabetes?

Most experts believe the frequency of the exercise routine is more important that the specific kind of exercise one engages in. Ideally, the exercise program will include aerobic activities and include some weight training.

When should patients be discouraged from exercising?

Some patients have a higher risk of developing injuries from the stress of an intense exercise program. Such patients include those with preexisting diabetes eye disease, hypertension and other cardiovascular risks.  Obviously, those who have been  leading sedentary lifestyles. need to take it slow and easy.  All patients should be thoroughly evaluated by their physicians before beginning a new exercise program.

About the Author – Su Rollins writes for <a
href=”http://www.hypoglycemicdiet.org”>reactive hypoglycemic diet</a> ,
her personal hobby blog focused on tips to prevent and cure hypoglycemia
using the right diet and nutrition.

I would only add to the discussion that in some instances, hair loss is on an auto-immune basis (called alopecia areata if the hair loss is spotty or alopecia totalis if the loss is big time) and is strongly associated with certain other auto-immune disorders, particularly chronic lymphocytic thyroiditis (aka Hashimoto’s thyroiditis) and adrenal insufficiency.  If the hair loss is considerable and sustained over weeks-to-months, I would strongly recommend a visit to a dermatologist before embarking on potential therapeutic misadventures.

The second article which appeared in the New York Times Magazine on Sunday January 17, 2010 was written by Tom Dunkel and was entitled “Vigor Quest.” The article was a very interesting and surprisingly balanced discussion of the attempts by what appears to be an increasing number of people obsessed with prolonging their youth, or at least, their youthful performance in a variety of activities.  My interest in the subject is, of course, as an endocrinologist (not as an aging endocrinologist).  Much of the discussion in the article focused on testosterone and growth hormone, drugs about which much has been written in both the medical and non-medical literature.  The subject has been in the news quite a bit recently with the controversy surrounding use of these drugs in professional athletes.  There is no question that deficiency of either testosterone or growth hormone can impair athletic performance and affect overall vigor.  The still unanswered questions are whether taking one or both of these substances when there is no apparent deficiency can be helpful and if there are potentially serious side-effects.  It is good that the National Institutes of Health has embarked on a long-term (6 years) study of the potential mental and physical benefits of testosterone therapy in elderly men.  They should also consider a companion study of growth hormone.  I for one strongly recommend that until we have much more scientific information, use of these biological agents be limited to patients who have definite deficiencies and symptoms and signs to match the laboratory findings.  But, I just wonder how fast I could swim if………?

Bus drivers vs. conductors

Dr. Morris was a British epidemiologist who hypothesized in the 1940’s that one could prove that exercise was heart-healthy by studying  bus drivers and conductors on London double-decker buses.  Drivers spend 90% of their workday sitting down while conductors walked up and down the bus stairs about a million times each day (actually about 600 stairs per day).  In a paper published in 1953, Dr. Morris showed that heart attack rates were dramatically lower in the conductors.  Follow-up studies showed that although the conductors, on average weighed less than the drivers, the rates were not closely related to weight or body type, including waist size.  He later studied postal workers, clerks and telephone operators vs. those who delivered the mail by walking or by bicycling.   The delivers had much lower risks of heart attack.  The strongest proof for the relationship between physical activity and risk for heart attack came from studies Dr. Morris conducted in the 1960s.  He looked at heart attack risks in a large group of men with sedentary government jobs in relation to their degree of aerobic activities outside work.  He found that those who performed vigorous exercise on a regular basis had a 50% risk reduction for heart attack.  The importance of Dr. Morris’s studies cannot be overemphasized.  In my opinion, most of what we now know about exercise and cardiovascular health was the direct result of his ground-breaking work.

The limitations of epidemiologic studies

Not to diminish the importance of Dr. Morris’s work, I need to remind you that epidemiologic studies cannot prove cause and effect but only show relationships.  For example, maybe bus drivers, postal clerks, and office workers are under more stress than bus conductors and postal delivery personnel?  And maybe people who have sedentary government jobs and who don’t exercise regularly just have different personality types (e.g., ‘type A” vs  whatever) than those who do exercise regularly and that is the reason for the study findings?  Anyway, it’s a pretty good bet that it’s the exercise per see that lowers the heart attack risk.  By the way, it may just be a fluke but Dr. Morris exercised regularly his whole life and lived to 99 and ½ and didn’t die of heart disease.

What do the data show?

The results are, perhaps, not entirely surprising, but they are very, very scary.  The report includes 50 million people so the data aren’t flawed by small numbers.  About two-thirds are overweight (fit into the overweight or obese categories based on BMIs); about one-third have no health insurance.   About 29% of men and 21% of women smoke cigarettes (smoking in women has decreased significantly over the past 10 years).  Among men, about 25% binge drink.  One of the study co-principal investigators, John Schulenberg, from the University of Michigan summed up the data pretty well when he said the following: “They’re still smoking, still drinking, still taking illicit drugs, and not exercising.  Whatever we’re doing, we’re not getting through to this particular age group.”

What do these data tell us?

In my opinion, these frightening data should tell us two things.  First, that  we should expect future health care costs related to “life-style” issues to remain very high for many years to come.  There is no reason to expect that when these young adults become mid-aged adults they will be healthier.  In fact, we should expect them to begin to show some of the consequences of their poor health behaviors such as heart disease, diabetes, and such.

The second thing these data tell us is that our current health care system has been incredibly ineffective in promoting healthy behaviors.  In my opinion, as we wrestle with how to reform our health care system, the discussions must include potential strategies to improve health behaviors.   I believe the most effective approach will be to develop comprehensive health education programs in the schools;, starting in kindergarten or even earlier; waiting until people are already overweight, smoking, drinking, and whatever, is too late; it’s almost always easier to prevent a problem than to treat it.  It’s much cheaper too!

The effects of exercise on blood glucose

We will start with the assumptions that a person with type 1 diabetes can do any physical activities that a person without diabetes can do and at as as high a level of performance. This has been demonstrated many times in the laboratory and “on the field.” But, to achieve optimal performance, a person with diabetes must learn how to keep his blood glucose level in a reasonable range throughout the activity. This can be quite a challenge and requires much “trial and error” in figuring out what to do about the insulin dosing and caloric intake.

When a person exercises, the metabolic rate increases in proportion to the intensity and or duration of the exercise. This requires enegy which comes from stored carbohydrates, fats, and proteins. Initially, the major share of the stored energy comes from glucose in the blood stream. Unfortunately, there is only a very small amount of glucose in the blood and hypoglycemia (low blood glucose) would develop quickly unless the body could match, molecule for molecule, production of glucose to equal that used up for energy. Initially, that glucose comes from stored glucose in the form of glycogen (long chains of glucose molecules) in the liver and in muscle. As the exercise continues, the body converts stored fats and proteins into energy to fuel the exercising msucles while leaving enough to maintain the blood glucose level in a normal range (proteins can be converted into glucose through a process called gluconeogenesis). This is quite a feat and involves many hormonal and neuronal mechanisms. The key to all of these adaptations is insulin. With exercise and increased glucose utilization, the body decreases insulin secretion which allows stored glucose and other nutrients to be used for energy and to maintain the blood glucose level.

If I go out and jog 10 kilometers (6.2 miles), my blood glucose level will be well maintained or even may go up a bit and I don’t even need to think about it- my body has figured out just how much to lower my insulin level to allow the required amounts of glucose to be made available for the exercise while maintaining my blood glucose level. But, what if I had diabetes and took insulin injections or used an insulin pump and couldn’t count on my body to figure things out? That’s the challenge for a person with type 1 diabetes who wants to exercise.

Getting down to specifics

Today, I do not want to go into great detail on how a person with diabetes figures out how to keep his blood glucose level from falling too low (or climbing too high) while providing enough metabolic fuels for the exercise. Obviously, it involves some combination of adjusting insulin doses and caloric intake. Sometimes, people with diabetes can anticipate the exercise and lower the insulin doses before and during the exercise. Such an adjustment in insulin may allow the normal mechanism of releasing stored glucose into the blood to work as in people without diabetes. Sometimes, taking in calories to mimic the release of stored glucose is necessary (e.g, ingestion of glucose-containing liquids or solids). For very long periods of exercise, ingestion of foods containing protein and fat may also be necessary. My point is that with some practice in figuring out the insulin/calorie factors, anyone with type 1 diabetes can expect to do as much exercise as they choose and do it well.

Most physicians who specialize in managing patients with type 1 diabetes should be quite experienced in helping their patients develop exercise plans. Particularly with the introduction of insulin infusion pumps and multiple injection insulin regimens over the past 25 years, the task is much easier than it used to be. In 2007, no one should be telling people with type 1 diabetes that they can’t do this or can’t do that, and that includes vigorous exercise programs.

What does interval training have to do with “prediabetes?”

The paragraph above really has nothing to do with prediabetes except that in the article, the author wrote the following: “weight watchers, prediabetics, and those who simply want to increase their fitness all stand to gain,” referring to the technique of interval training. I would be willing to bet that most of the people who read the article do not have any idea what prediabetes is. I’m here to help.

Prediabetes is an old term in the diabetes field but which has been “reinvented” recently. It used to mean a more-or-less theoretical state in which a person was at genetic risk for developing diabetes mellitus or “sugar diabetes” (to distinguish it from diabetes insipidus, a condition related to water balance) but had normal blood sugar levels. More recently, the term is used to define a group of people who are at increased risk for developing diabetes based on specific blood sugar levels, which are above normal but not high enough to allow one to definitively diagnose diabetes. Are you with me so far?

Definitions

Diabetes is defined by certain blood sugar levels, either in the “fasting state,” which usually means with no caloric intake for the previous 12 hours, or after a standard sugar water drink called a glucose tolerance test. Technically speaking what is measured is the “plasma glucose level” even though many people talk about the “blood sugar level.” Anyway, for a variety of reasons, some scientifically sound and some more politically sound, a person is said to have diabetes if either the fasting plasma glucose is 126 mg/dl or greater on two occasions, or the value two hours after 75 grams of oral glucose is 200 mg.dl or greater. The diagnosis can also be made if a “casual” plasma glucose value (this means testing without regard to interval since the previous meal) is 200 mg/dl or greater with typical symptoms of diabetes- excessive thirst, excessive urination, etc.  There are a number of conditions that need to be met before the diagnosis can be made, such as the person must be well-nourished, not acutely ill, etc. Also, a definitive diagnosis cannot be made using the little portable blood glucose meters that we see advertised on TV; the test must be carried out in a laboratory with actual measurement of the plasma glucose level.

Impaired fasting plasma glucose, impaired glucose tolerance, and prediabetes

This brings us to “prediabetes” states. Diabetes experts define impaired fasting plasma glucose (IFG) as fasting plasma glucose of 100-125 mg/dl; impaired glucose tolerance (IGT) is defined as fasting plasma glucose <126 mg/dl but 2-hour plasma glucose after a glucose tolerance test of 140-199 mg/dl. Finally, prediabetes is defined as either IFG, IGT, or both. Recent studies show that people who have prediabetes are at great risk to develop diabetes within a few years. As it turns out, things are not quite so simple. For example, if the fasting plasma glucose is 100-109 mg/dl, the risk for progression to diabetes from IFG is rather low- much higher if the fasting plasma glucose is in the range 110-125 mg/dl.

So?

THe reason it is important to understand these definitions is that recent studies have shown that treating patients with prediabetes can slow progression to diabetes. Thus the very recent American Diabetes Association’s Consensus Statement entitled ” Impaired Fasting Glucose and Impaired Glucose Tolerance” (Diabetes Care 30:753-759) in which it is recommended to treat all people who have either IFG, IGT, or both.  Depending on a number of factors, the treatment would be lifestyle modification and moderate intensity phycical activity (defined as roughly 30 minutes/day) or the above and medications. All of this is to decrease the risk for progression from prediabetes to the real thing, diabetes.

So?

These are bold recommendations that if followed by all medical practitioners would lead to an astonishing increase in testing for IFG and IGT. What I find so amazing is that despite these recommendations, the American Diabetes Association (ADA) and many of the experts who wrote the Consensus Statement discussed above are ambivalent about testing for prediabetes. To quote the recently published ADA’s Clinical Practice Recommendations 2007 (Diabetes Care 30 (suppl 1.):S1-S104, 2007) for diabetes screening: “Screening to detect prediabetes (IGF or IGT) should be considered in individuals >45 yeares of age, particularly in those with a BMI >25 kg/mXm.” They go on to say that screening should be considered in people <45 years of age who are overweight if they have other risk factors for diabetes. How seriously should we take a recommendation of "should be considered."? On the one hand the "experts" tell us we should be treated for prediabetes but our doctors should only "consider" testing us for it. Does any of this make sense to you?

What should we do?

Given that about 60% of people in the U.S. are overweight and that we have a diabetes epidemic, we should (not should consider) begin testing on a regular basis (e.g., every 1-2 years) for prediabetes or diabetes in all adults who are overweight. It is the only logical thing to do based on the available scientific information. Why are the “experts” so afraid to speak up? I’m not sure but I suspect there are powerful health-care industry lobbyists who do not feel insurers can cope with the expense of making so many diagnoses of prediabetes and diabetes and then having to treat the patients? Of course, they need not worry; our health-care system is so disorganized that we couldn’t possibly find a way to actually carry out the testing and provide the proper treatment. Am I being unfair? I don’t think so.

Recently, my son John, who lives in the San Francisco Bay area and is an avid bicycle rider, asked me if I could explain to him something about the technique of heart rate monitoring with exercise. Apparently, many of his friends hold to the theory that a work-out is not worth doing unless one can monitoir his heart rate to be certain the activity is being performed optimally. John told me he was completely baffled about the subject. As a good father, I told him I would do what I could to allay his anxiety about the quality of his bicycle rides.

First- the short answer

I reminded John that I had discussed heart rate monitoring in an earlier entry about using an exercise bicycle. I suggested that for most people it was quite sufficient to first calculate their maximum heart rate (220 minus age in years) and aim for a heart rate of 60-70% of the calculated maximum to assure a ride that would contribute to cardiovascular fitness. John, who is quite serious about his level of cardiovascular fitness, told me he had read the entry but really wanted quite a bit more information.

More information than almost anyone needs about heart rate monitoring

First, I need to say something that may upset many serious exercisers. It is fine to carry out heart rate monitoring during exercise (unless one falls off his bicycle or the treadmill while checking the pulse), but for most people it is not very important. For all but elite athletes and those in cardiac rehabilitation, very little heart rate monitoring is necessary. Now that I’ve offended lots of people, including manufacturers of heart rate monitoring equipment, I need to defend my audacious statement.

Heart rate monitoring is used during exercise as a measure of work rate and oxygen uptake, which are really what we want to know but which can only be assessed properly in a laboratory. So, heart rate (HR) is a surrogate measure of energy expenditure. Its main virtue is that it is easy to measure. HR does increase linearly with work rate and oxygen consumption but the HR response to exercise depends on many factors including age, body position during exercise, level of fitness, environmental factors (e.g., air temperature, relative humidity, altitude), whether or not heart disease is present, medications, blood volume, and on and on.

What happens to the heart rate with training?

At rest, energy expenditure is very low (1-2 kcal/minute) with the skeletal muscles contributing very little, about 20%. With exercise, things change drastically. Energy expenditure can increase 10-30X, mostly for the muscles. For this to happen, the muscles need more oxygen which can only occur if the heart gets more blood to the muscles. The heart has a limited bag of tricks for increasing blood flow to muscles. For one, it can shunt blood from certain parts of the body, i.e., the gut, to the muscle. The heart can also increase its rate, resulting in more blood, hence more oxygen, to the muscles per unit time.

With training, the heart can also enlarge, allowing more blood to be ejected per beat (the amount of blood ejected per beat is called the stroke volume or SV). This is very important since the heart needs more oxygen during exercise just like the rest of the muscles. The blood vessels that supply the heart muscle with oxygen are called the coronary arteries. These arteries fill only during diastole, the resting phase of the heart. The more rapid the heart rate, the shorter and shorter the diastolic phase and the less time for the heart to feed itself. The trained heart with its greater SV can pump as much blood as the untrained heart but at a much lower heart rate, thereby increasing the supply of oxygen to the heart muscle. Pretty nifty, huh? In addition, the trained heart has decreased oxygen demand at rest and during exercise.
Resting heart rate

As you would suspect based on the fact that the conditioned heart is larger and thus ejects more blood per unit time, the resting heart rate is lower in people who are fit. The “normal” heart rate is about 65-75 beats/minute; the highly conditioned athlete can have a heart rate as low as 40 beats/minute and still deliver as much oxygen as the body needs in the resting state. If the resting heart rate is consistently less than 60 beats/minute, that suggests reasonable cardiovascular fitness assuming the low heart rate is not due to some disease of the heart or some medication (my son’s was 48 beats/minute).

Aging

With increasing age, the heart changes: the maximal heart rate decreases, the maximal SV decreases, and as you would expect, the maximal cardiac output (measured as the amount of blood pumped/minute) decreases- in a 65 year old the cardiac output is 10-30% less than in a 30 year old. The maximal SV also decreases with age.

Recommendations

We could go on and on and discuss many other aspects of cariovascular fitness. We didn’t even get into “METS” or metabolic equivalents which are a measure of the metabolic cost of activity. Put in another way, a MET is an estimate of the intensity of an activity looking at a ratio of the working metabloic rate to the resting rate.  One MET is equivalent to a certain amount of oxygen uptake (3.5 mL/kg/min, if you are interested).  Studies have determined how many METs are used in various activities.  For example, using a stationary bicycle with very light effort uses 3 METs while vigorous effort uses 10.5 METs.  walking the dog uses 3 METs and walking at a 4 mile per hour pace (considered a brisk pace) uses 5 METs.  Maybe we’ll come back to METs sometime?

For those of you who are not aiming for a gold medal at the next olympics, I would relax a bit about quantifying your cardiovascular effort with each exercise session. I would calculate maximum heart rate and try to sustain at least 60-70% of that for at least 20-30 minutes. If at that level of physical activity you barely raise a drop of sweat, maybe you need to rethink your maximal heart rate. Remember, the 220 minus age in years for maximum heart rate is just a rough guideline. Also, it is important to keep track of your resting heart rate- after 2-3 months of fitness training, it should be under 60 beats/minute. One other thing- if after exercising 30-60 minutes at 60-70% of your calculated maximum heart rate your heart rate is still quite a bit over your usual resting heart rate (e.g., greater than 100 beats/minute) 30 minutes out, you may have overdone it or you may be a bit dehydrated.

Summary

Well, maybe I was a bit brash in denegrating the use of heart rate monitoring with exercise. Maybe I should have said, heart rate monitoring can be useful but don’t go crazy with it? One other thing- I never did discuss how to monitor heart rate. As I discussed in my exercise bicycle entry, checking the radial pulse is the easiest and cheapest way- the index and third finger of one hand placed on the wrist of the opposite hand thumb side. You’ll find the radial artery pumping away. If you count for 10 seconds and multiply that by 6 you have a heart rate; the longer you count, the more accurate the estimate of the heart rate. I think expensive fancy monitors are just fine but very optional (if these gadgets are fun to use and increase the pleasure in the exercise, they are probably worth the cost even if they do not directly do much to improve cardiovascular fitness).

Resources

For those who want to explore the subject of cardiovascular/fitness training in depth, I recommend the American College of Sports Medicine (ASCM) Resource Manual For Guidelines For Exercise Testing And Prescription, Fifth Edition, Lippincott Williams & Wilkins, 2006. This is “the bible” for exercise testing and is both comprehensive and readable (and expensive- $59.00). You can access the ACM at www.acsm.org.

What’s so great about an exercise bike?

An exercise bike is an easy way for almost anyone to get a good workout that is “low impact.” What I mean by low impact is that the exercise does not require beating down one’s knees and hips as occurs with running. It is a good way for people to get exercise if they have upper extremity injuries that might limit some types of exercise and for people who might have difficulty with other low impact forms of exercise such as walking (e.g., foot problems). Exercise bikes are also cheap- one can spend a fortune on one, but used bikes are readily available and new ones can be found at reasonable prices. For those who are members of recreational facilities, tracking down an exercise bike should be easy. I wonder how many Americans actually have an old exercise bike in their basement, garage, or attic, just gathering dust?

What about bike specifics?

I personally have had little experience with recumbent bikes, but some people swear by them. Here I will focus on the more traditional upright stationary bikes. The keys to a good bike include a comfortable and adjustable seat, a mechanism to adjust the effort necessary to turn the pedals, good pedals which include a straps that fit over the feet (similar or identical to “toe clips” often found on mountain bikes) making the ride more comfortable and providing an exercise “bonus” of work when the pedal is going up as well as when it is going down and around. If the seat is not comfortable or if it is old and falling apart, you may be able to have a bike shop fit a seat from a regular bike (mountain bike seats are often very comfortable). The bike shop can also help you get better pedals or add straps if the bike does not have them. Bikes that have fancy computers to set exercise programs, monitor heart rate, distance “traveled,” calories burned, and so forth, are nice but not essential.

What’s next?

Let’s assume that you have a bike with the essentials as discussed above. The first step is to adjust the seat height. Sit on the bike and find the seat height that allows your foot (either) to rest horizontally on the pedal with only a very slight bend to the knee. This adjustment will allow you to pedal smoothly without having to raise up from the seat and without injuring your knees. The proper seat height adjustment is very important.

Next you need to adjust the handlebars so they are comfortable (on some bikes the handlebars are not adjustable, so just skip this step). Most people prefer to lean forward and grasp the handlebars rather than sitting strictly upright; people who read books when riding an exercise bike usually sit up fairly straight but I don’t think that’s a very comfortable position. Whatever works for you is just fine.

Ready to ride

Next, just start pedaling. The mechanism for adjusting the work of pedaling should be set low (on the fancy bikes one just punches in a work effort level). You should be able to pedal without much effort. Over 1-2 minutes, increase your pedaling speed to about 50-60 revolutions/minute (you should pick your left or right foot and count the number of times it goes completely around in 10 seconds- it should be about 10 revolutions. If you want to time things longer, feel free (e.g., 30 revolutions in 30 seconds). Your eventual goal is to spin the pedals at 70-90 revolutions/minute for most of the bike ride. Personally, I feel 75-80 revolutions is about right. It’s not so critical exactly what the revolution rate is but 100 revolutions per minute is too fast and 40 is way too slow unless you are way out of shape and want to gradually work up to full speed (the best approach).

How hard to pedal?

The tricky part is figuring how hard to pedal. What you need to aim for is a heart rate of about 60% of maximum after you have been at it for about 15 minutes. How does one do that? Well, you can calculate maximum heart rate as 220-age; then take 60% of that number as your target heart rate to assure an aerobic workout. For example if you are age 40 years, your calculated maximum heart rate is 220-40 = 180 beats/minute. Sixty percent of 180 is 108 beats/minute. So, you need to pedal with enough tension in the pedaling at the pedaling rate we have already discussed to keep you heart rate roughly in the 110-120 beats/minute range. If after 10-15 minutes of pedaling, you heart rate is 90 beats/minute, crank it up. These are just guidelines and what’s right is different for every person.

How long to pedal?

I usually ride for about 30 minutes. I warm up for about 5 minutes, gradually increasing the speed of the pedal rotation and the work of pedaling (on my old Schwinn, there is a dial that is connected to a cable that works a braking mechanism on the wheel). I ride at about 80 pedal revolutions/minute and at a heart rate of about 130 beats/minute (maybe a bit too fast for an old man like me). For the last 5 minutes of the ride, I increase the tension a bit and the pedal rotation speed a bit (to 90 rotations/minute) just to prove that I am a tough guy. Finally, I do a 2-3 minute warm-down, turning the pedalling tension way down and drastically slowing the pedal rotation. After 30 minutes of cycling you should be pretty sweaty unless you keep a fan blowing. Within 5-10 minutes, your heart rate should be back to normal (roughly 60-75 beats/minute). If not, you were doing a much harder workout than you should have been doing given your level of cardiovascular fitness.

A word of caution

Unless you know you are in great shape (cardiovascular-wise), check with your doctor before beginning any exercise program and pace yourself. You shouldn’t be having chest pain during the exercise or be extremely out of breath.

Gear

I completely forgot to discuss what to wear for your cycling adventures. I suggest regular biking shorts and maybe, biking tights under them. You want to be comfortable and do not want your inner thighs to get sore. As far as shoes go, I prefer to wear cycling shoes- not the weird Italian racing bike shoes, but rather, bike shoes designed for mountain bikers (many of these types of shoes come with optional gear to use the shoes with clip-in pedals). You can also use running shoes, but I like the cycling shoes because they have very firm soles where your feet sit on the pedals. You shouldn’t need to spend more than $50-60 and the shoes will last you 300 years. I wear thin wicking-type socks (fabrics such as wool, Cool-Max (TM), etc., but not cotton) and a grungy old tee shirt.

I also almost forgot the most important part- what do do while you are pedalling. I usually listen to music with headphones. I have recently rediscovered my thousands of old cassette tapes. They work fine- I keep the tape player in a little waist bag. Some people enjoy watching TV while they cycle. Some people listen to music and watch TV. Some people just pedal and think. Do whatever suits you.

How often to ride?

I have no specific recommendations regarding the frequency with which one should use their exercise bike. It really depends on whether the cycling is the major component of a person’s fitness plan, or just one of a variety of exercise options. In general, people should strive for at least 3, 30 minute exercise sessions/week- the U.S. government (I can’t remember which agency) now recommends that most adults exercise 60 minutes every day. This is not a very realistic recommendation (apparently, in the U.S. the average adult does no regular exercise and walks about 750 yards per day (that comes to about 3 miles per week). It’s pretty pathetic. Soon, we’ll come back to exercise as it relates to our current epidemics of obesity and diabetes.