Tag Archives: physical activity

Exercise, Part 10: What If I’m Markedly Obese?

The more overweight you are, the harder it will be to exercise.  At some point even light exercise becomes impossible.  Average-height women tipping the scales at about 280 pounds (127 kg) and men at 360 pounds (164 kg) aren’t going to be able to jog around the block, much less run a marathon.  These weights are 100 percent over ideal or healthy levels.  An actual “exercise program” probably won’t be possible until some weight is lost simply through very-low-carb eating, calorie restriction, or bariatric surgery.  The initial exercise goal for you may just be to get moving through activities of daily living and perhaps brief walks and calisthenics while sitting in a chair.

"I'll get started after I finish this cigarette."

Markedly obese people who aren’t up to the aforementioned extreme weights can usually tolerate a low-intensity physical activity program.  At 50 percent over ideal weight, an average-height woman of 210 pounds (95 kg) is carrying 70 excess pounds (32 kg) of fat.  Her male counter-part lugs around 90 pounds (41 kg) of unnecessary fat.  This weight burden causes dramatic breathlessness and fatigue upon exertion, and makes the joints and muscles more susceptible to aching and injury.  If you’re skinny, just imagine trying to walk or run a mile carrying a standard five-gallon (19 liter) water cooler bottle, which weighs only 43 pounds (19.5 kg) when full.  The burden of excess fat makes it quite difficult to exercise.    

If you’re markedly obese, several tricks will enhance your exercise success.  I want you to avoid injury, frustration, and burn out.  Start with light activity for only 10 or 15 minutes, gradually increase session length (e.g., by two to four minutes every two to four weeks) and increase exercise intensity only after several months.  Your joints and muscles may appreciate easy, low-impact exercises such as stationary cycling, walking, swimming, and pool calisthenics/water aerobics.  You may also benefit from the advice of a personal fitness trainer arranged through a health club, gym, or YMCA/YWCA.  Check out several health clubs before you join.  Some of them are primarily meat markets for beautiful slender yuppies.  You may feel more comfortable in a gym that welcomes and caters to overweight people. Hospitals are increasingly developing fitness centers with obese orthopedic, heart, and diabetic patients in mind.

Steve Parker, M.D.

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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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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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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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