Tag Archives: exercise

April 8, 2011 · 2:00 AM

Exercise, Part 9: Realistic Goals If You’re New to Exercise

FITNESS

Sustained physical activity requires that your heart pump blood to the lungs and to the exercising muscles.  The muscles extract oxygen, sugar, and other nutrients for use in chemical reactions that enable the muscle to keep moving (contracting).  To say that someone is physically fit simply means that the heart easily pumps a large volume of blood and the muscles extract and use nutrients very efficiently.  The heart, after all, is just a hollow muscle that pumps blood.  If you stimulate your heart muscle through exercise, it will become more powerful and able to pump more blood.  Regular sessions of physical activity increase the metabolic efficiency and power of your other muscles, too.  There are various degrees of fitness, with professional and Olympic athletes at the extreme upper end.

GETTING STARTED

I’ve had otherwise healthy overweight patients so “out of shape” that walking 20 yards to the mailbox was a real chore.  They were tired and panting when they got to the mailbox and had to rest a bit before returning to the house.  These folks are habitually sedentary and dramatically overweight.  But you need not feel too sorry for them.  After starting and maintaining an exercise program, these unfit people achieve the greatest degree of improvement in fitness level.  They make more progress, and faster, than those who begin with a greater level of fitness.

The way to achieve aerobic fitness is to regularly challenge your large muscles to perform sustained physical activity.  “Regularly” means at least four days a week, if not daily.  Left alone, your muscles don’t want to do much other than just get you through your day comfortably, without effort or aching or cramps.  You must challenge them to do more, work a bit harder, tolerate a little aching.  You’ll know you’re challenging them during exercise when you perceive that mild to moderate effort is required to keep the activity going.  You should be mildly short of breath, perhaps even perspiring lightly, yet still able to converse.  “Sustained” physical activity means at least 30 minutes in a day.  Most people find it a better use of their time to exercise for 30 minutes continuously rather than break it up into five or 10 minutes here and there.

Discontinuous activity (e.g., 10 minutes thrice daily) probably is just as good. If you think about it, there are many easy ways to increase your discontinuous physical activity. Consider taking the stairs instead of the elevator, parking far from the supermarket or workplace doors, walking the golf course instead of riding a cart.

(The exercise model above is “old school,” which isn’t necessarily good or bad.  Some newer scientific studies suggest that you can achieve comparable levels of fitness with much less time exercising, if you do it intensely.  An example is high-intensity interval training (HIIT).  That’s worth a blog post or two by itself.  I also leave strength training—also an important aspect of fitness—for another day.)

If you’re starting out in poor shape, you won’t be able to do 30 minutes of any exercise without adverse effects.  Don’t even try.  The worst thing you could do at this point is injure yourself or have such a horrible experience that you give up entirely.  Thirty minutes of daily activity is your goal to achieve over the next four to 12 months.  Moderate to high levels of fitness will take you six to 24 months.  The most important thing when getting started is to exercise at least a little, five to 10 minutes, on most days of the week.  And don’t overdo it in terms of intensity. Start low, go slow.  After three months, exercise will be a habit.  Prolongation of your exercise sessions will be easy as your amazing body responds gradually to the workload through the process called physical conditioning.

If walking 30 minutes daily is too hard for you at first, try walking just an extra 10 or 20 minutes daily.  If you can do that but it’s a bit of a strain, gradually (every two weeks) increase your walking time by five minutes daily until you are up to 30 minutes.  Average walking pace is 2 mph (3.2 km/h).  Once you can comfortably handle 30 minutes daily, the next step is to increase your walking pace to 3 or 4 mph (4.8–6.4 km/h) for the entire 30 minutes.  Four mph (6.4 km/h) is definitely a brisk walk.  It’s difficult for many people to sustain over 30 minutes until they work up to it gradually.  This is often done by walking at two paces, normal and brisk, during an exercise session.  You might walk five minutes at normal pace, then five minutes briskly, alternating every five minutes until the session is over.  Every two to four weeks, you can increase the minutes of brisk pace and taper off the normal pace.  You’re able to do this easily because your level of fitness is increasing.

I’m asking you to walk briskly (3–4 mph or 4.8–6.4 km/h) for 30 minutes most days of the week.  This brisk pace burns roughly 200 calories per session, in case you’re wondering.  If you eat a 400-calorie muffin, it provides enough energy for a one-hour brisk walk.  If you don’t burn the muffin calories as exercise or basal metabolism, they’ll turn into body fat.  (But you’re not eating muffins anymore, are you?!)

If you prefer physical activity other than walking, the general rule is to start slowly and gradually increase your effort (intensity) until you’re up to about 30 minutes of moderate-intensity exercise most days of the week.  Start low, go slow.

Steve Parker, M.D.

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March 20, 2011 · 7:41 AM

Exercise, Part 8: Warnings and Precautions for Diabetics

Exercise clearly has many benefits, as discussed in prior installments of this series.  Yet we shouldn’t overlook the potential risks to diabetics either. 

Diabetic Retinopathy

Diabetics with retinopathy (an eye disease caused by diabetes) have an increased risk of retinal detachment and bleeding into the eyeball called vitreous hemorrhage. These can cause blindness. Vigorous aerobic or resistance training may increase the odds of these serious eye complications. Patients with retinopathy may not be able to safely participate. If you have any degree of retinopathy, avoid the straining and breath-holding that is so often done during weightlifting or other forms of resistance exercise. Vigorous aerobic exercise may also pose a risk. By all means, check with your ophthalmologist first. You don’t want to experiment with your eyes.

Diabetic Feet and Peripheral Neuropathy 

Diabetics are prone to foot ulcers, infections, and ingrown toenails, especially if peripheral neuropathy (numbness or loss of sensation) is present. Proper foot care, including frequent inspection, is more important than usual if a diabetic exercises with her feet. Daily inspection should include the soles and in-between the toes, looking for blisters, redness, calluses, cracks, scrapes, or breaks in the skin. See your physician or podiatrist for any abnormalities. Proper footwear is important (for example, don’t crowd your toes). Dry feet should be treated with a moisturizer regularly. In cases of severe peripheral neuropathy, non-weight-bearing exercise (e.g., swimming or cycling) may be preferable. Discuss with your physician or podiatrist.

Hypoglycemia

Low blood sugars are a risk during exercise if you take diabetic medications in the following classes: insulins, sulfonylureas, meglitinides, and possibly thiazolidinediones and bromocriptine. Hypoglycemia is very uncommon with thiazolidinediones. Bromocriptine is so new (for diabetes) that we have little experience with it; hypoglycemia is probably rare or non-existent. See drug details in chapter four. Diabetics treated with diet alone or other medications rarely have trouble with hypoglycemia during exercise.

Always check your blood sugar before an exercise session if you are at risk for hypoglycemia. Always have glucose tablets, such as Dextrotabs, available if you are at risk for hypoglycemia. Hold off on your exercise if your blood sugar is over 200 mg/dl (11.1 mmol/l) and you don’t feel well, because exercise has the potential to raise blood sugar even further early in the course of an exercise session.

As an exercise session continues, active muscles may soak up bloodstream glucose as an energy source, leaving less circulating glucose available for other tissues such as your brain. Vigorous exercise can reduce blood sugar levels below 60 mg/dl (3.33 mmol/l), although it’s rarely a problem in non-diabetics.

The degree of glucose removal from the bloodstream by exercising muscles depends on how much muscle is working, and how hard. Vigorous exercise by several large muscles will remove more glucose. Compare a long rowing race to a slow stroll around in the neighborhood. The rower is strenuously using large muscles in the legs, arms, and back. The rower will pull much more glucose out of circulation. Of course, other metabolic processes are working to put more glucose into circulation as exercising muscles remove it. Carbohydrate consumption and diabetic medications are going to affect this balance one way or the other.

If you are at risk for hypoglycemia, check your blood sugar before your exercise session. If under 90 mg/dl (5.0 mmol/l), eat a meal or chew some glucose tablets to prevent exercise-induced hypoglycemia. Re-test your blood sugar 30–60 minutes later, before you exercise, to be sure it’s over 90 mg/dl (5.0 mmol/l). The peak effect of the glucose tablets will be 30–60 minutes later. If the exercise session is long or strenuous, you may need to chew glucose tablets every 15–30 minutes. If you don’t have glucose tablets, keep a carbohydrate source with you or nearby in case you develop hypoglycemia during exercise.

Re-check your blood sugar 30–60 minutes after exercise since it may tend to go too low.

If you are at risk of hypoglycemia and performing moderately vigorous or strenuous exercise, you may need to check your blood sugar every 15–30 minutes during exercise sessions until you have established a predictable pattern. Reduce the frequency once you’re convinced that hypoglycemia won’t occur. Return to frequent blood sugar checks when your diet or exercise routine changes.

These general guidelines don’t apply across the board to each and every diabetic. Our metabolisms are all different. The best way to see what effect diet and exercise will have on your glucose levels is to monitor them with your home glucose measuring device, especially if you are new to exercise or you work out vigorously. You can pause during your exercise routine and check a glucose level, particularly if you don’t feel well. Carbohydrate or calorie restriction combined with a moderately strenuous or vigorous exercise program may necessitate a 50 percent or more reduction in your insulin, sulfonylurea, or meglitinide. Or the dosage may need to be reduced only on days of heavy workouts. Again, enlist the help of your personal physician, dietitian, diabetes nurse educator, and home glucose monitor.

Finally, insulin users should be aware that insulin injected over muscles that are about to be exercised may get faster absorption into the bloodstream. Blood sugar may then fall rapidly and too low. For example, injecting into the thigh and then going for a run may cause a more pronounced insulin effect compared to injection into the abdomen or arm.

Autonomic Neuropathy

This issue is pretty technical and pertains to function of automatic, unconscious body functions controlled by nerves. These reflexes can be abnormal, particularly in someone who’s had diabetes for many years, and are called autonomic neuropathy. Take your heart rate, for example. It’s there all the time, you don’t have to think about it. If you run to catch a bus or climb two flights of stairs, your heart rate increases automatically to supply more blood to exercising muscles. If that automatic reflex doesn’t work properly, exercise is more dangerous, possibly leading to passing out, dizziness, and poor exercise tolerance. Other automatic nerve systems control our body temperature regulation (exercise may overheat you), stomach emptying (your blood sugar may go too low), and blood pressure (it could drop too low). Only your doctor can tell for sure if you have autonomic neuropathy.

Steve Parker, M.D.

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March 6, 2011 · 2:00 AM

Exercise, Part 7: Could Exercise Hurt Me?

To protect you from injury, I recommend that you obtain “medical clearance” from a personal physician before starting an exercise program.  A physician is in the best position to determine if your plans are safe for you, thereby avoiding complications such as injury and death.  Nevertheless, most adults can start a moderate-intensity exercise program with little risk.  An example of moderate intensity would be walking briskly (3–4 mph or 4.8–6.4 km/h) for 30 minutes daily.

Men over 40 and women over 50 who anticipate a more vigorous program should consult a physician to ensure safety.  The physician may well recommend diagnostic blood work, an electrocardiogram (heart electrical tracing), and an exercise stress test (often on a treadmill).  The goal is not to generate fees for the doctor, but to find the occasional person for whom exercise will be dangerous, if not fatal.  Those who drop dead at the start of a vigorous exercise program often have an undiagnosed heart condition, such as blockages in the arteries that supply the heart muscle.  The doctor will also look for other dangerous undiagnosed “silent” conditions, such as leaky heart valves, hereditary heart conditions, aneurysms, extremely high blood pressure, and severe diabetes.

The American Diabetes Association’s Standards of Care—2011 states that routine testing of all diabetics for heart artery blockages before an exercise program is not recommended; the doctor should use judgment case-by-case.  Many diabetics (and their doctors) are unaware that they already have “silent” coronary artery disease (CAD).  CAD is defined by blocked or clogged heart arteries, which reduced the blood flow to the hard-working heart muscle.  Your heart pumps 100,000 times a day, every day, for years without rest.  CAD raises the odds of fainting, heart attack, or sudden death during strenuous exercise.  I recommend a cardiac stress test (or the equivalent) to all diabetics prior to moderate or vigorous exercise programs, particularly if over 40 years old. CAD can thus be diagnosed and treated before complications arise.  Ask your personal physician for her opinion.

Regardless of age and diabetes, other folks who may benefit from a medical consultation before starting an exercise program include those with known high blood pressure, high cholesterol, joint problems (e.g., arthritis, degenerated discs), neurologic problems, poor circulation, lung disease, or any other significant chronic medical condition.  Also be sure to check with a doctor first if you’ve been experiencing chest pains, palpitations, dizziness, fainting spells, headaches, frequent urination, or any unusual symptoms (particularly during exertion).

Physicians, physiatrists, physical therapists, and exercise physiologists can also be helpful in design of a safe, effective exercise program for those with established chronic medical conditions. 

Steve Parker, M.D.

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March 2, 2011 · 8:40 AM

Exercise, Part 6: Make It a Habit

So, I’ve convinced you that regular physical activity offers some great health benefits and you’re ready to get started. A couple weeks of intensive effort on your part, but then quitting, isn’t going to do you any good. In fact, it’s more likely to do harm (injury) than good.

The main objective at this point is to make regular physical activity a habit. Establishment of a habit requires frequent repetition over at least two or three months, regardless of the weather, whether you feel like it or not. Over time the chosen activity becomes part of your identity.

To avoid injury and burn out, begin your exercise program slowly and increase the intensity of your effort only every two or three weeks. Your body needs time to adjust to its new workload, but it will indeed adjust. Enhance your enjoyment with proper attire, equipment, and instruction, if needed. Use a portable radio or digital music system like an iPod or Zune if you tend to get bored exercising.

The “buddy system” works well for many of my patients: agree with a friend that you’ll meet regularly for walking, jogging, whatever. If you know your buddy is counting on you to show up at the park at 7 a.m., it may be just the motivation you need to get you out of bed. Others just can’t handle such regimentation and enjoy the flexibility and independence of solitary activity.

If you like to socialize, join a health club or sports team. Large cities have organized clubs that promote a wide range of physical activities. Find your niche.

Don’t be afraid to try something new. Expect some disappointment and failed experiments. Learn and grow from adversity and failure. Put a lot of thought into your choice of activity. Avoid built-in barriers. If you live in Florida you won’t have much opportunity for cross-country skiing. If joining a health club is a financial strain, walk instead. Perhaps pick different activities for cold and warm weather. Or do several types of exercise to avoid boredom.

 In summary, formation of the exercise habit requires forethought, repetition, and commitment. You must schedule time for physical activity. Make it a priority. Hundreds of my couch potato patients have done it, and I’m sure you can, too. I’ve seen 40-year-old unathletic, uncoordinated barnacles start exercising and run marathons two years later. (A marathon is 26.2 miles or 42.2 km.)

Part 7 of the series covers “medical clearance.”

Steve Parker, M.D.

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January 30, 2011 · 7:34 PM

Exercise, Part 3: How Much Is Enough?

Now that you know the health benefits of exercise (see Parts 1 & 2 of this series), it’s a little easier to understand those crazy people you see jogging at 6 a.m. in below-freezing weather. I’m sure you’re ready to join them tomorrow morning. Right?

Here’s some good news. Most people following both the Ketogenic and Low-Carb Mediterranean Diets are able to lose excess weight and improve glucose control without starting an exercise program. Many—but certainly not all—will be able to maintain a stable, reasonable weight and glucose control long-term without ongoing exercise. However, for the reasons previously outlined, I recommend you start a physical activity program eventually.

Later in the series I discuss 1) who needs to get medical clearance from their personal physician before starting an exercise program, and 2) how certain diabetic complications make exercise more dangerous.

(I must warn you that athletic individuals who perform vigorous exercise should expect a deterioration in performance levels during the first three to four weeks of any very-low-carb ketogenic diet. The body needs that time to adjust to burning mostly fat for fuel rather than carbohydrate. Also, competitive weight-lifters or other anaerobic athletes (e.g., sprinters) will be hampered by the low muscle glycogen stores that accompany ketogenic diets. They need more carbohydrates for high-level performance.)

How Much Exercise?

All I’m asking you to do is aerobic activity, such as walk briskly (3–4 mph or 4.8–6.4 km/h) for 30 minutes most days of the week, and do some muscle-strengthening exercises three times a week. These recommendations are also consistent with the American Diabetes Association’s Standards of Care–2011. This amount of exercise will get you most of the documented health benefits. It’s OK if you want to wait until you’ve lost some of your excess weight, but I probably wouldn’t.

For the general public without diabetes, the U.S. Centers for Disease Control and Prevention recommends at least 150 minutes per week of moderate-intensity aerobic activity (e.g., brisk walking) and muscle-strengthening activity at least twice a week, OR 75 minutes per week of vigorous-intensity aerobic activity (e.g., running or jogging) plus muscle-strengthening activity at least twice a week. The muscle-strengthening activity should work all the major muscle groups: legs, hips, back, abdomen, chest, shoulders, arms.

Please note that you don’t have to run marathons (26.2 miles) or compete in the Ironman Triathlon to earn the health benefits of exercise. However, if health promotion and disease prevention are your goals, plan on a lifetime commitment to regular physical activity.

Parts 4 & 5 of this series review strength training and aerobic exercise.

Steve Parker, M.D. 

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January 27, 2011 · 2:38 AM

Exercise, Part 2: The Fountain of Youth and Other Metabolic Effects

Part 1 of the Exercise series focused on how regular physical activity prevented or postponed death. Onward now to other benefits.

Waist Management

Where does the fat go when you lose weight dieting? Chemical reactions convert it to energy, water, and carbon dioxide, which weigh less than the fat. Most of your energy supply is used to fuel basic life-maintaining physiologic processes at rest, referred to as resting or basal metabolism. Basal metabolic rate (BMR) is expressed as calories per kilogram of body weight per hour.

The major determinants of BMR are age, sex, and the body’s relative proportions of muscle and fat. Heredity plays a lesser role. Energy not used for basal metabolism is either stored as fat or converted by the muscles to physical activity. Most of us use about 70 percent of our energy supply for basal metabolism and 30 percent for physical activity. Those who exercise regularly and vigorously may expend 40–60 percent of their calorie intake doing physical activity. Excess energy not used in resting metabolism or physical activity is stored as fat.

Insulin, remember, is the main hormone converting that excess energy into fat; and carbohydrates are the major cause of insulin release by the pancreas.

To some extent, overweight and obesity result from an imbalance between energy intake (food) and expenditure (exercise and basal metabolism). Excessive carbohydrate consumption in particular drives the imbalance towards overweight, via insulin’s fat-storing properties.

In terms of losing weight, the most important metabolic effect of exercise is that it turns fat into weightless energy. We see that weekly on TV’s “Biggest Loser” show; participants exercise a huge amount. Please be aware that conditions set up for the show are totally unrealistic for the vast majority of people.

Physical activity alone as a weight-loss method isn’t very effective. But there are several other reasons to recommend exercise to those wishing to lose weight. Exercise counteracts the decrease in basal metabolic rate seen with calorie-restricted diets. In some folks, exercise temporarily reduces appetite (but others note the opposite effect). While caloric restriction during dieting can diminish your sense of energy and vitality, exercise typically does the opposite. Many dieters, especially those on low-calorie poorly designed diets, lose lean tissue (such as muscle and water) in addition to fat. This isn’t desirable over the long run. Exercise counteracts the tendency to lose muscle mass while nevertheless modestly facilitating fat loss.

How much does exercise contribute to most successful weight-loss efforts? Only about 10 percent on average. The other 90 percent is from food restriction.

Fountain of Youth

Regular exercise is a demonstrable “fountain of youth.” Peak aerobic power (or fitness) naturally diminishes by 50 percent between young adulthood and age 65. In other words, as age advances even a light physical task becomes fatiguing if it is sustained over time. By the age of 75 or 80, many of us depend on others for help with the ordinary tasks of daily living, such as housecleaning and grocery shopping. Regular exercise increases fitness (aerobic power) by 15–20 percent in middle-aged and older men and women, the equivalent of a 10–20 year reduction in biological age! This prolongation of self-sufficiency improves quality of life.

Heart Health

Exercise helps control multiple cardiac (heart attack) risk factors: obesity, high cholesterol, elevated blood pressure, high triglycerides, and diabetes. Regular aerobic activity tends to lower LDL cholesterol, the “bad cholesterol.” Jogging 10 or 12 miles per week, or the equivalent amount of other exercise, increases HDL cholesterol (“good cholesterol”) substantially. Exercise increases heart muscle efficiency and blood flow to the heart. For the person who has already had a heart attack, regular physical activity decreases the incidence of fatal recurrence by 20–30 percent and adds an extra two or three years of life, on average.

Effect on Diabetes

Eighty-five percent of type 2 diabetics are overweight or obese. It’s not just a random association. Obesity contributes heavily to most cases of type 2 diabetes, particularly in those predisposed by heredity. Insulin is the key that allows bloodstream sugar (glucose) into cells for utilization as energy, thus keeping blood sugar from reaching dangerously high levels. Overweight bodies produce plenty of insulin, often more than average. The problem in overweight diabetics is that the cells are no longer sensitive to insulin’s effect. Weight loss and exercise independently return insulin sensitivity towards normal. Many diabetics can improve their condition through sensible exercise and weight management.

Miscellaneous Benefits

In case you need more reasons to start or keep exercising, consider the following additional benefits: 1) enhanced immune function, 2) stronger bones, 3) preservation and improvement of flexibility, 4) lower blood pressure by 8–10 points, 5) diminished premenstrual bloating, breast tenderness, and mood changes, 6) reduced incidence of dementia, 7) less trouble with constipation, 7) better ability to handle stress, 8) less trouble with insomnia, 9) improved self-esteem, 10) enhanced sense of well-being, with less anxiety and depression, 11) higher perceived level of energy, and 12) prevention of weight regain.

People who lose fat weight but regain it cite lack of exercise as one explanation. One scientific study by S. Kayman and associates looked at people who dropped 20 percent or more of their total weight, and the role of exercise in maintaining that loss. Two years after the initial weight loss, 90 percent of the successful loss-maintainers reported exercising regularly. Of those who regained their weight, only 34 percent were exercising.

 Part 3 of this series gets into specific exercise recommendations.

Steve Parker, M.D.

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January 24, 2011 · 4:42 AM

Exercise, Part 1: Exercise Postpones Death

Earlier this month, many folks made New Years’ resolutions to start exercising in conjunction with their other resolution to lose excess weight. I’ve got bad news for them.

Exercise is overrated as a pathway to major weight loss.

Sure, a physically inactive young man with only five or 10 pounds (2 to 4 kg) to lose might be able to do it simply by starting an exercise program. That doesn’t work nearly as well for women. The problem is that exercise stimulates appetite, so any calories burned by exercise tend to be counteracted by increased food consumption.

"Should I go with aerobic or strength training....?"

On the other hand, exercise is particularly important for diabetics and prediabetics in two respects: 1) it helps in avoidance of overweight, especially after weight loss, and 2) it helps control blood sugar levels by improving insulin resistance, perhaps even bypassing it.

Even if it doesn’t help much with weight loss, regular physical activity has myriad general health benefits. First, let’s look at its effect on death rates.   

EXERCISE PREVENTS DEATH

As many as 250,000 deaths per year in the United States (approximately 12% of the total) are attributable to a lack of regular physical activity. We know now that regular physical activity can prevent a significant number of these deaths.

Exercise induces metabolic changes that lessen the impact of, or prevent altogether, several major illnesses, such as high blood pressure, coronary artery disease, diabetes, and obesity. There are also psychological benefits. Even if you’re just interested in looking better, awareness of exercise’s other advantages can be motivational.

Exercise is defined as planned, structured, and repetitive bodily movement done to improve or maintain physical fitness.

Physical fitness is a set of attributes that relate to your ability to perform physical activity. These attributes include resting heart rate, blood pressure at rest and during exercise, lung capacity, body composition (weight in relation to height, percentage of body fat and muscle, bone structure), and aerobic power.

Aerobic power takes some explanation. Muscles perform their work by contracting, which shortens the muscles, pulling on attached tendons or bones. The resultant movement is physical activity. Muscle contraction requires energy, which is obtained from chemical reactions that use oxygen. Oxygen from the air we breathe is delivered to muscle tissue by the lungs, heart, and blood vessels. The ability of the cardiopulmonary system to transport oxygen from the atmosphere to the working muscles is called maximal oxygen uptake, or aerobic power. It’s the primary factor limiting performance of muscular activity.

Aerobic power is commonly measured by having a person perform progressively more difficult exercise on a treadmill or bicycle to the point of exhaustion. The treadmill test starts at a walking pace and gets faster and steeper every few minutes. The longer the subject can last on the treadmill, the greater his aerobic power. A large aerobic power is one of the most reliable indicators of good physical fitness. It’s cultivated through consistent, repetitive physical activity.

Physical Fitness Effect on Death Rates

Regular physical activity postpones death.

Higher levels of physical fitness are linked to lower rates of death primarily from cancer and cardiovascular disease (e.g., heart attacks and stroke). What’s more, moving from a lower to a higher level of fitness also prolongs life, even for people over 60.

Part 2 of this series will cover all the other health benefits of exercise. Part 3 will outline specific exercise recommendations, such as the type and duration of activity.

Steve Parker, M.D.

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November 30, 2010 · 7:39 AM

Aerobic vs Strength Training: Which Improves Diabetes More?

Judging from improvement in hemoglobin A1c, the combination of aerobic and strength training is needed to improve diabetic blood sugar levels.  Both types of exercise—when considered alone—did not improve diabetes control, according to the latest research in the Journal of the American Medical Association.

One type of resistance training

One of the things that impressed me about Dr. Richard Bernstein’s book, Diabetes Solution, was his strong advocacy of weight training, also known as resistance training and strength training.  Weight lifting is a typical example.

Prior studies had shown exercise-induced  improvements (reductions)  in hemoglobin A1c, a great test for overall diabetes control, in the range of o.66% to 1.0% (absolute change, not relative).  That’s comparable to what we see with many drugs.  Much easier to pop a pill though, huh?

One earlier study showed hemoglobin A1c lowered by 0.4% with resistance training, 0.5% with aerobic training, and 1.0% with combined resistance/aerobic.  But folks doing both aerobic and resistance were exercising 270 minutes a week—39 minutes a day—which was significantly more than the people just doing one type of exercise. [This was the DARE study: Diabetes Aerobic and Resistance Exercise.] 

Investigators at the Pennington Biomedical Research Center in Louisiana wondered which type of exercise would be more effective, comparing the same minutes per week of activity.

Methodology

They randomized 262 sedentary type 2 diabetics to one of four groups: control, aerobic exercise, resistance training 3 days a week, or combined aerobic and resistance training (resistance twice weekly).  All three groups exercised for about 140 minutes a week—just 20 minutes a day, on average—for nine months.  Exercise intensity was 50 to 80% of maximum oxygen consumption (determined by a baseline treadmill stress test).  Nearly all participants were on diabetic drugs; 18% were on insulin.  I think the aerobic group exercised on treadmills.

Participant characteristics:  Women were 64% of the total.  Average age 56. Forty-seven percent were non-white (114 black, 10 Hispanic/other).  Average body mass index was 35.  Average hemoglobin A1c was 7.7%.  Not too many people dropped out of the study before it was over.

Results

No serious adverse event occurred during exercise.  The authors didn’t mention the occurence of hypoglycemia.

The combination training group dropped their hemoglobin A1c average by 0.34% (p = 0.03). The pure resistance and aerobic exercisers didn’t show any improvement over the control group.

The combination group lost 1.6 kg body weight on average compared to the control group.  Pure resistance and aerobic exercisers’ weights didn’t differ from the control group. [Remember, this was not a weight-loss study.]

Comments

The authors write:

The failure of the aerobic group to lose a substantial amount of weight (or fat) has been reported in numerous aerobic exercise trials, which may be due to aerobic training resulting in [higher] energy intake, expenditure compensation, or both.

If you’re trying to lose excess fat weight, resistance training appears to win over aerobic exercise.

Doing either aerobic execise or resistance exercise for an average of 20 minutes a day will not improve hemoglobin A1c levels in most type 2 diabetics.  We can assume blood sugars aren’t lower either.  It takes a combination of both types of exercise to lower hemoglobin A1c.

A hundred and forty minutes of exercise weekly—just 20 minutes a day—is not too much to ask for, if improved health and weight management are the goals.  More would be better.

Over nine months, the control group ended up needing more diabetic drugs.  The combination training group decreased its drug use.

Dr. Bernstein may still by right to stress resistance training over aerobic.  I bet he’d say these folks weren’t exercising enough.  The study at hand suggests that it’s important to do both types of exercise, especially if you’re not going to put much time into it.

The details of the resistance training program are probably important.  You can read the study yourself and decide if participants were on a good regimen.  I’ve little expertise in that area. 

ResearchBlogging.orgDiabetics taking insulin, sulfonylureas, and meglitinides are at risk for hypoglycemia during exercise. The study authors made little mention of this, so it may be safe to assume it wasn’t a problem. Certified diabetes educators saw participants monthly, which may have nipped the problem in the bud.

Steve Parker, M.D.

Reference: Church, T., Blair, S., Cocreham, S., Johannsen, N., Johnson, W., Kramer, K., Mikus, C., Myers, V., Nauta, M., Rodarte, R., Sparks, L., Thompson, A., & Earnest, C. (2010). Effects of Aerobic and Resistance Training on Hemoglobin A1c Levels in Patients With Type 2 Diabetes: A Randomized Controlled Trial JAMA: The Journal of the American Medical Association, 304 (20), 2253-2262 DOI: 10.1001/jama.2010.1710

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