Running

Considered one of the most time-efficient exercises, running is an excellent way to get fit. The average adult burns about 100 calories per mile (or about 700 per hour at a moderate pace), and you can see a vast improvement in aerobic fitness in a matter of weeks. But when other responsibilities are running your life, and time for a trek is in short supply, here's how to make the most of your mileage:

• Invest in some intervals: Instead of just hitting the road at a steady stride, mix up your pace with short and fast intervals. Run full-blast for about 30 seconds, and then jog or even walk for another minute. Your overall distance may be less, but you'll get a more intense workout in less time. If you're running on a curved track, run the straight-aways at full speed and jog the curves; if you're running on a street, sprint for several telephone poles and walk for a few more.
  
• Include hills: You'll get more from your workout by choosing a hilly course, or at least including hills in your runs. Elite runners often sprint up a hill for about 30 seconds, and jog down. (Don't run down hills, because it increases risk of injury.) If you're running on a treadmill, you can include inclines every few minutes to get a better workout.
  
• Wear ankle weights: If you're in good shape and want to really challenge yourself, wear ankle weights and run up and down the steps of a high school stadium or bleachers. But do this with caution, because there's added stress on your joints.
  
• Be a softie: If possible, avoid running on hard surfaces like asphalt and concrete sidewalks; softer surfaces such as grass, a dirt track or indoor tracks at health clubs reduces risk of shinsplints and knee pain.
  

Study: Half of Overweight Adults May Be Heart-Healthy, Defying Conventional Wisdom

You can look great in a swimsuit and still be a heart attack waiting to happen. And you can also be overweight and otherwise healthy. A new study suggests that a surprising number of overweight people -- about half -- have normal blood pressure and cholesterol levels, while an equally startling number of trim people suffer from some of the ills associated with obesity.

The first national estimate of its kind bolsters the argument that you can be hefty but still healthy, or at least healthier than has been believed.

The results also show that stereotypes about body size can be misleading, and that even "less voluptuous" people can have risk factors commonly associated with obesity, said study author MaryFran Sowers, a University of Michigan obesity researcher.

"We're really talking about taking a look with a very different lens" at weight and health risks, Sowers said.

In the study, about 51 percent of overweight adults, or roughly 36 million people nationwide, had mostly normal levels of blood pressure, cholesterol, blood fats called triglycerides and blood sugar.

Almost one-third of obese adults, or nearly 20 million people, also were in this healthy range, meaning that none or only one of those measures was abnormal.

Yet about a fourth of adults in the recommended-weight range had unhealthy levels of at least two of these measures. That means some 16 million of them are at risk for heart problems.

It's no secret that thin people can develop heart-related problems and that fat people often do not. But that millions defy the stereotypes will come as a surprise to many people, Sowers said.

Even so, there's growing debate about the accuracy of the standard method of calculating whether someone is overweight. Health officials rely on the body mass index, a weight-height ratio that does not distinguish between fat and lean tissue. The limits of that method were highlighted a few years ago when it was reported that the system would put nearly half of NBA players in the overweight category.

A number of experts say waist size is a more accurate way of determining someone's health risks, and the study results support that argument.

Dr. Robert Eckel, a former American Heart Association president and professor of medicine at the University of Colorado, said the new research may help dismiss some of the generalizations that are sometimes made about weight and health.

Study co-author Judith Wylie-Rosett emphasized that the study shouldn't send the message "that we don't need to worry about weight." That's because half of overweight people do face elevated risks for heart disease, explained Wylie-Rosett, a nutrition researcher at Albert Einstein College of Medicine in New York.

But, for those without elevated risks, losing weight "might be important only from a cosmetic perspective," she said.

To arrive at the estimates, scientists analyzed nationally representative government surveys involving 5,440 people age 20 and over, and extrapolated to calculate nationwide figures.

The new study, appearing in Monday's Archives of Internal Medicine, used government surveys from 1999 to 2004 that included lab tests and height and weight measurements. Participants reported on habits including smoking and physical activity.

In all weight categories, risk factors for heart problems were generally more common in older people, smokers and inactive people. Among obese people who were 50 to 64, just 20 percent were considered healthy compared with half of younger obese people.

The results underscore how important exercise is for staying healthy, even for people of healthy weight, Wylie-Rosett said.

The authors noted that fat tissue releases hormones and other substances that affect things like blood vessels, cholesterol and blood sugar. The results suggest this interaction varies among overweight and obese people, the authors said.

The results also add to mounting evidence that thick waists are linked with heart risks.

Among people of healthy weight in the study, elevated blood pressure, cholesterol and other factors were more common for people with larger waists or potbellies. This often signals internal fat deposits surrounding abdominal organs, which previous research has shown can be especially risky.

Similarly, among overweight and obese adults, those in the "healthy" category tended to have smaller waists than those with at least two risk factors.

Dr. Lewis Landsberg, a Northwestern University obesity expert, noted that the research didn't look at heart disease, and that not everyone with high risk factors develops heart problems.

Still, he said, the study shows that waist measurements can help assess health.

Reaching the Limits of Exercise

• Improving Oxygen Delivery
  
• Dealing With the Sense of Effort
  
• Putting It Together
  

When your mind and body tell you, "I can't take another step or complete another rep," do you listen to your body or push beyond it, thinking, no pain, no gain? There is no right answer, but learning why you feel you've reached your limit will help move you to a higher fitness level.

Improving Oxygen Delivery

Cells break down sugars and fats to create energy, and they do that most efficiently when oxygen is present. This is called aerobic metabolism, a process that goes on perpetually throughout our bodies. Without oxygen, cells can still burn calories for energy — called anaerobic metabolism. But parts of the body can only function for short bursts of time under anaerobic conditions before energy production declines.

Oxygen delivery has long been considered the most important factor that limits exercise.

Oxygen in the air must make its way to individual muscle cells. After the lungs deliver the oxygen to the blood, the heart and the arteries move the oxygen-rich blood to the contracting muscles.

The lungs, heart, and arteries have maximal capacities. Once the maximal capacity of any one of these three components is reached, the muscles won't get any incremental increase in oxygen no matter how much they crave it. To keep the muscles contracting, the cells switch to anaerobic metabolism. In this state, the cells produce lactic acid, which causes muscle pain and fatigue.

The more athletically fit you are, the more efficiently your body delivers oxygen to your muscles. To increase your exercise capacity you want to maximize the oxygen delivery. This starts with getting more oxygen deep into the lungs. Be aware of your breathing as you exercise. Inhale through your nose, reaching a natural pause, then take another short inhale, and slowly let the air exhale through your mouth. As exertion increases, this becomes a challenge, because the increased oxygen demand will cause you to breathe faster. Try to stick with the technique even at the quicker breathing rate.

The heart can increase the amount of blood pumped to the arteries in two ways: by increasing the rate of heart contractions and by expanding the volume of blood that is pushed out with each heartbeat. With fitness training, the heart will enlarge over time so that it can push more out, but cranking up your heart rate is the predominant way that your heart does its part to improve oxygen delivery.

When an inactive person tries to exercise vigorously (NOT recommended), heart rate rises very quickly and hits the maximal rate within several minutes. Unlike your breathing, you can't voluntarily tell your heart rate to slow down. To achieve a more gradual heart rate rise during exercise, you need to improve your overall fitness. With improved physical conditioning, you increase both exertional effort and exercise time without a racing pulse.

During exercise, the walls of normal arteries relax to allow the heart to pump blood with less resistance, increasing blood flow and oxygen delivery to the working muscles. There are no specific techniques to improve artery function, but you can harm it. Smoking makes arteries stiffer by impairing their ability to relax. In addition, studies show that lower LDL cholesterol and triglycerides and higher HDL cholesterol are associated with healthier arteries.

Dealing With the Sense of Effort

When you are exercising and you reach the point where you feel you cannot move another muscle, your brain is perceiving "exercise effort." This sense of exercise effort is related to both the duration of time you have exercised and the level of power output. This sense of effort is an unpleasant sensation that causes you to decide to stop exercising when it becomes intolerable. Like any painful or unpleasant sensation, your willingness to put up with the sense of effort is subjective and influenced by cognitive and emotional factors. People vary widely in how much "exercise effort" they can stand.

The nerve pathways involved in perception of effort are connected to both the skeletal muscles and the muscles that control breathing. Our brain will sense that the effort is coming from one or the other, or both at the same time. Without stopping your exercise activity, you can quickly lessen the unpleasant sense of effort by temporarily slowing down. The reason is that power output has a much more dramatic affect on sense of effort than does length of time doing the exercise. Small decreases in power output rapidly diminish sense of effort and allow you to continue exercising. This relationship is true for both breathing and skeletal muscle performance. So if you are running or pedaling on a bike, slow down a little to relieve the sense of effort. And then increase your pace again after a few minutes.

Stronger, conditioned muscles are much more able to use oxygen efficiently (aerobic metabolism). It is when muscles run out of oxygen and are operating without it (anaerobic metabolism) that lactic acid is created, which reinforces the sense of effort. By strengthening your muscles, you will decrease the point at which your brain perceives the effort sensation.

Putting It Together

A progressive exercise session, where you start at a lower power output and gradually increase your effort, enables you to think about the limiting factors I described. During your walk, pick up your pace a little and think about your breathing — in through your nose twice and out through your mouth. If you can, check your heart rate, either by wearing a heart rate monitor or feeling your pulse. Stay at the faster pace until the sense of effort kicks in. The sense of effort is not chest pain or some other pain — that kind of pain should make you stop immediately. But the sense of effort is a sensation you will need to get beyond to reach a higher level of fitness.