Thursday, February 28, 2008

Muscle Fatigue May Be Caused By Calcium Loss

New research from Columbia University in New York shows that muscle fatigue during and after exercise may be caused by loss of calcium from muscle cells and that drugs that block the release of calcium from muscle cells may prolong endurance (Proceedings of the National Academy of Sciences, February 11, 2008).

When you exercise, your cells use food to generate electricity that causes nerves to send messages and muscles to contract. The energy from food generates electricity by driving minerals inside and outside of the cells, creating an imbalance of the minerals between the outside and inside of cells that causes electrons (electricity) to flow. A major source of this flow of electrons is from muscle cells pushing calcium outside their cell walls. This paper shows that muscles lose calcium continuously during exercise, and eventually do not have enough calcium to continue pumping calcium outside of cells, and therefore cannot generate as much electricity. This causes the muscles to weaken, hurt, lose coordination and feel tired.

The authors timed mice exercising to the point of exhaustion. Then they gave the mice an experimental drug that blocks the loss of calcium from muscle cells, and they were able to exercise longer. The researchers demonstrated the same process of calcium loss in the muscles of trained cyclists. However, they have not taken the next step of testing the drug to see if it improved endurance, because the drug has not been approved for use in humans. More fitness reports

Tuesday, February 26, 2008

Artificial Sweeteners May Cause Weight Gain

A study of 9514 middle-aged Americans from the University of Minnesota showed that those that drank diet sodas regularly were at high risk for developing diabetes in later life (Circulation, February 2008). How can this be? Diet drinks do not contain sugar, and it is a high rise in blood sugar after meals that markedly increases a person's chances of developing diabetes. But who is most likely to drink diet sodas? A person who is overweight and trying to lose weight. So the study does not show that diet sodas cause diabetes. It shows that people who try the hardest to lose weight (and often fail) are the ones most likely to drink diet soda.

However, researchers at Purdue University showed that mice fed artificial sweeteners ate more and put on weight. They believe that a sweet taste causes the brain to seek out more food (Behavioral Neuroscience, February, 2008). The authors propose that: "a sweet taste in the mouth helps prime the metabolism for the arrival of a calorie-heavy, sweet meal into the digestive system." This study needs to be repeated with humans to see if the sweet taste from artificial sweeteners actually causes people to eat more. Weekly newsletter

Thursday, February 21, 2008

Do You Inherit a Tendency to be Fat?

Nobody has really proven why some people eat a lot and are skinny, while other eat little and are fat. The simplistic explanation of eating less and exercising more to control weight doesn't work for all people. Researchers at Maastricht University in the Netherlands think that some people burn a greater percentage of the food that they eat than others. They showed that people who are fat burn a lower percentage of the calories that they take in than those who are skinny. They used deuterated palmitic acid, given with breakfast, to measure percentage of calories burned.
Journal reference

Future studies must explain whether some people are genetically destined to be fat because they burn fewer calories, or whether any person who becomes fat will then burn fewer of the calories they take in. That could explain why overweight people continue to get fatter even if they eat less than their thinner peers. More

Wednesday, February 20, 2008

Maximum heart rate gets lower as you get more fit

A study from Liverpool, England shows that the maximum heart rate for athletes is lower than for aged-matched sedentary people. At first glance, this makes no sense because you would think that the faster you heart can beat, the more blood your heart could pump and the better an athlete you would be. However, a stronger heart pumps more blood with each beat, so stronger hearts don't have to beat as often. This means that as you become more fit, your maximum heart rate will get lower, not higher.

Virtually everyone agrees that heart rate depends on the amount of blood pumped toward it by exercising muscles. When you contract your leg muscles during exercise, muscles squeeze veins near them to pump blood toward the heart. Then when leg muscles relax, the veins fill up with blood. The pumping action of leg muscles during exercise forces extra blood to the heart, which causes the heat to beat faster and contract stronger. This is known as the Bainbridge reflex. We know this is true because we are able to transplant hearts. If nerves inside the heart regulated heart rate, the heart would not be able to control its rate of beating since the nerves are cut during the transplant.

Since the strength of leg muscles determines the fastest that your heart can beat and still pump blood, you might expect that athletes with stronger muscles would have faster heart rates. However, they don't. The researchers at John Moores University in Liverpool showed that athletes have lower maximum heart rates than sedentary people (International Journal of Sports Medicine, January 2008). The maximum heart rate of male athletes was calculated to be 202 - 0.55 × age, and for female athletes, 216 - 1.09 × age. Both weight lifters and runners had similar maximum heart rates, which were significantly lower than the age-matched sedentary people. The athletes have hearts that can pump more blood with each beat than the hearts of sedentary people, so they do not beat as often.

Thursday, February 14, 2008

How to Recover from an Injury or Surgery

Is it better to rest completely or exercise gently while recovering from an injury? According to a study from the University of Wisconsin in Madison, it is better to exercise at low intensity while recovering from an injury or surgery. The researchers found that motion during recovery limits muscle atrophy, accelerates tendon healing, and prevents joint stiffness. This explains why most doctors refer their injured or post-surgical patients for physical therapy and rehabilitation exercises.

If you are in reasonable shape and stop exercising for any reason, your muscles become smaller and weaker and are at increased risk for injury when you return to exercising. Gentle stress on a muscle or tendon can help to prevent this loss of strength. Mild exercise is a stimulus for cell growth. However, if you pull too hard on a weakened muscle or tendon, you can tear it and delay recovery.
Journal reference

Monday, February 11, 2008

Cold Air Won't Freeze Your Lungs During Exercise

It's almost impossible to damage your lungs by breathing cold air when you exercise. More than 70 percent of the energy produced by your muscles during exercise is lost as heat. This extra heat can be used in your nose and bronchial tubes to warm the air as it travels to your lungs. Air inhaled at 40 degrees below zero Fahrenheit will be warmed to more than 100 degrees by the time it reaches your lungs, so your lungs will not suffer from frostbite.

However, air that cold will burn your nasal membranes and cause pain in your nose that is so severe that you will lose interest in exercising very quickly and look for shelter. To protect your nose in very cold weather, you can cover it with a scarf, balaclava or face mask placed over your nose and mouth.
More on frostbite

Sunday, February 10, 2008

Longer Telomeres Mean Longer Life

If you need proof that exercise helps to keep you young, look at the exciting study from King's College in London, England reported in the Archives of Internal Medicine (January 28, 2008). The researchers showed that people who exercise regularly have telomeres in the DNA of their white blood cells that are longer than those of couch potatoes. White blood cell telomeres shorten over time and serve as a marker of a person's biological age.

The active ends of genetic material in cells are covered with a layer of proteins called telomeres. If they weren't, the exposed ends of the genetic material would stick to anything nearby and the cells would die. However, each time a cell divides to make two cells, a little bit of the telomere is removed. Eventually the telomere is gone, the ends of genetic material stick together and the cell can no longer divide so it dies without replacing itself. Obviously, the longer the telomeres, the longer it will take for the telomeres to be used up so the cells are viable longer.

The study compared physical activity, smoking and socioeconomic status in 2,401 sets of twins. Those who were more active had longer leukocyte telomeres than those who were less active. The researchers concluded that "The mean difference in leukocyte telomere length between the most active (who performed an average of 199 minutes of physical activity per week) and the least active (16 minutes of physical activity per week) subjects was 200 nucleotides, which means that the most active subjects had telomeres the same length as sedentary individuals 10 years younger, on average."
More fitness reports

Wednesday, February 06, 2008

Dry Skin Means Lack of Water, Not Lack of Oil

Dry skin means lack of water, not lack of oil. Skin creams function by creating a temporary barrier on your skin that seals in water.

In the late 1940's, a doctor at Massachusetts General Hospital took a hard callus off the foot of one of his patients and placed in oil. It remained as hard as ever. Then he placed the callus in water and it became very soft, but soon after being removed from the water, it became very hard again. Then he left the callus in water until it became soft, removed it and then soaked it in oil and it remained soft for a long time. He had shown that dry skin should be treated by using oils and creams to seal in moisture. Cosmetic manufacturers soon produced oil-in-water emulsions which were incorporated into creams designed to seal in water.

However, some studies show that oil-in-water emulsions soak off the outer layer of skin and increase its susceptibility to irritation from cold, rubbing, and various chemicals that you may be exposed to, such as ingredients in cleaning products or cosmetics. The longer skin is immersed in water, the more protective outer coatings of skin is stripped off. Take quick showers and decide for yourself whether using a cream or lotion helps you or not.

All lotions and creams work the same way, no matter how much they cost or what special ingredients they claim to contain. Just pick one that feels and smells pleasant to you.

Monday, February 04, 2008

How exercise prevents diabetes: more than just weight control

A fascinating study from Maastricht University in the Netherlands shows that exercise helps to prevent and treat diabetes by increasing the number of enzymes that transport fat from fat cells to muscle cells where it can be used for energy by the muscles. Before insulin can do its job of removing sugar from the bloodstream and putting it into cells where it can be burned for energy, it must first attach on special hooks called insulin receptors on the surface of cells. Fat stored in cells internalizes receptors so insulin loses its attachment sites and is unable to its job. Exercise causes muscle cells to markedly increase their production of certain fat transported proteins that remove fat from fat and muscle cells. So less fat is available to block insulin receptors and blood sugar levels drop. Journal reference

Another study, from University of California at Berkeley, followed 36,000 male runners for almost a decade. Those who ran five or more miles per week were half as likely to develop diabetes as those who ran fewer than five miles per week (Diabetes Care, November 2007). Furthermore, researchers at the University of Western Australia showed that an eight-week exercise program markedly increased diabetics' ability to respond to insulin, even if they did not lose any fat. Journal reference

Anyone who wants to prevent diabetes should make exercise a priority. Because of the extremely high rate of heart disease in diabetics, all diabetics should have their hearts checked by a cardiologist. If they can pass a thalium stress test, they should be in some kind of supervised exercise program. More

Knee Cartilage Repair: Will it Work for You?

The ends of bones are soft, so they must be covered with a thick white gristle called cartilage. Once damaged, cartilage can never heal. When knee cartilage is damaged, the person spends the rest of his life losing more cartilage until it is completely gone and the knee hurts 24 hours a day.

If only a small area of the cartilage is damaged, it may be repaired with cartilage extracted from your own body. (If cartilage is taken from someone else, your immunity will try to kill it, but it doesn’t try to kill your own cartilage.) Your extracted cartilage is grown in special culture dishes and then injected into a hole in your own cartilage and secured in place. This procedure works very well if you have only a small piece of cartilage missing. The doctors just fill the hole. However, unless they can enclose the entire area for the donor site, the cartilage will not stay where it was put and will not be beneficial. That is why this procedure cannot be used to treat a cracked cartilage in the knee. Remember they have to cover the articular surface that meets the cartilage from the other side of a joint.

When all the cartilage in your knee is gone, the only effective treatment is to replace the whole knee. Knee replacements are now lasting for twelve to twenty years or more, and most remain pain-free.

If you have damaged cartilage in your knee, you should protect that knee for the rest of your life. Running, fast walking and jumping cause further damage, while pedaling and swimming usually do not. When the knee hurts all the time, your doctor will check to see how much cartilage is left. If it's gone, you probably need a knee replacement.