Thursday, August 30, 2007

Finger length may indicate athletic ability

High levels of the male hormone, testosterone, cause the fourth finger of unborn children to grow more than the second. This explains why men usually have proportionately longer fourth fingers than women do. Scientists can use the length of the fourth finger to tell which women were exposed to higher levels of testosterone before they were born. Researchers at the University of Central Lancashire in Preston, England showed that women whose fourth finger is much longer than their second were faster cross country runners in races of one to four miles (American Journal of Human Biology, May-June 2007).

The finger length was measured from the bottom crease where the finger joins the hand to the tip of the finger. Men are typically bigger and stronger than women, and have larger muscles and bones, because of their higher testosterone levels. Testosterone helps people to recover faster from hard workouts, so they can do more work and become better athletes. Women exposed to higher levels of testosterone in utero have higher ratios of their fourth to second fingers and often are better athletes.

Tuesday, August 28, 2007

Most common cause of muscle cramps: lack of salt

The most common cause of muscle cramps in exercisers is lack of salt, according to a report from the University of Oklahoma. The authors cite studies of tennis and football players showing that crampers tend to be salty sweaters, and of triathletes who cramp losing more salt during a race than peers who did not cramp. They found that intravenous saline can reverse cramping, and that more salt in the diet or in sports drinks can help to prevent heat cramping.

Until now, the leading theory was that most cases of muscle cramps in competitive athletes are caused by an exaggerated "stretch reflex". When you stretch a muscle, it pulls on its tendon. Stretch reflex nerves in that tendon send a message back to the spinal cord (not the brain), and then the "stretch reflex" in the spinal cord sends a message along nerves from the spine to cause the muscle to contract. During fatigue, the muscle retains its contraction to form a cramp. A study from South Africa showed that the most likely cause is muscle fatigue or tearing of the muscle itself. If this is true, muscle cramps during endurance events can be prevented by slowing down when you feel excessive soreness in one muscle group or straining in a muscle. Of course, competitive athletes will not do this, and they pay for it with muscle cramps.

For many years I have recommended eating salted peanuts or other salty foods during heavy exercise, but other doctors believe that extra salt will raise blood pressure. If this is a concern for you, get a wrist cuff monitor and check your blood pressure every day. You are likely to find that your blood pressure goes down, not up, with regular exercise even when you add salt. Journal reference; salt and blood pressure

Sunday, August 26, 2007

Acne patients improve on low-glycemic-index diet

Most dermatologists tell their patients that diet has nothing to do with acne, but researchers at RMIT University in Melbourne, Australia presented a paper showing that an experimental low glycemic–load diet helps to improve acne. After 12 weeks, those on the special diet had lower acne lesion counts, lower body weight and lower blood levels of male hormones, compared to those who were not on the special diet.

Acne is a skin disease in which a person's skin glands produce excessive amounts of oil that is converted from a colorless liquid to a more solid white sebum. Then the body causes an immune reaction that causes redness and swelling around the oil glands on the surface of the skin. High levels of male hormones increase oil secretion, while female hormones usually lower it. This study shows that foods that cause a high rise in blood sugar may increase male hormones, oil production and acne.
Journal reference; explanation of low-glycemic-index diet

Thursday, August 23, 2007

Fish Oil Supplements Can Raise LDL Cholesterol

Nobody really knows whether fish oil supplements prevent heart attacts as effectively as eating fish. However, both eating fish and taking fish oil pills can lower triglycerides and prevent clotting, which may help prevent heart attacks. Heart attacks occur when a plaque breaks off from the wall of arteries leading to the heart and travels down the ever-narrowing artery until it stops and forms a clot that blocks blood flow to the heart.

A recent report shows that nine grams of fish oil supplements per day may not be completely safe because they can cause a substantial rise in the bad LDL cholesterol (from 106 to 186) that increases heart attack risk (The Annals of Pharmacotherapy, July 2007). Fish oil supplements lower triglycerides by reducing liver cells' ability to manufacture triglycerides. At the same time, they can block the LDL receptors on liver cells from removing LDL from the bloodstream. Once again, I recommend getting the nutrients your body needs from food rather than from supplements. Diet to lower cholesterol; how to raise the good HDL cholesterol

Wednesday, August 22, 2007

Injuries more likely if you have only one sport

Triathletes are injured only about one third as often as marathon runners even though they do far more work in their program of swimming, cycling and running. Training intelligently for three sports is less likely to injure you than training very hard for one. Training is limited by damage to skeletal muscles. Every time you exercise, your muscles develop small tears with bleeding. It takes at least 48 hours for muscles to heal from exercise. Each sport stresses a particular group of muscles most. Marathon runners who train every day stress the same muscles and do not allow adequate time to recover from the previous day's workout, so they are at increased risk for injury.

Top triathletes train in different sports on consecutive days. Running stresses the lower leg muscles most, cycling stresses the upper leg muscles most and swimming stresses the arms and shoulders most. Triathletes usually set up a workout schedule that includes two sports on one day and one on the next. Of the three sports, running causes the most muscle damage. Muscles are protected by the water in swimming and by the rotary pedal motion in cycling. However, the force of the footstrike in running tears up muscles. So a knowledgeable triathlete runs on one day and cycles and swims on the next. This way each stressed muscle group has a 48-hour recovery before the next workout. You can apply these same rules for alternating any two or three different activities. Principles of training

Tuesday, August 21, 2007

Does High Fructose Corn Syrup Cause Obesity?

For the last 25 years, soft drinks have used high fructose corn syrup as their major form of sweetening. This coincides with a major increase in obesity in America. However, a study from the University of Washington shows that there is no evidence that commercial beverages sweetened with either sucrose or high fructose corn syrup have significantly different effects on hunger or how much you eat (American Journal of Clinical Nutrition, July 2007).

In another study from Purdue University, subjects were given three different food groups in both liquid and solid forms (International Journal of Obesity, June 2007). No matter what they ate, the subjects ate far more calories on the days that they took in foods in liquid form. This shows that liquid forms of food are interpreted in the brain as less filling, and therefore people take in more calories when their beverages contain calories. Interestingly, the increase in calories associated with liquid forms of foods was nearly the same in obese and skinny people.

A single 12-ounce can of soda contains 13 teaspoons of high fructose corn syrup and the average American consumes almost 60 pounds of it, according to the U.S. Department of Agriculture. The leading theory now is that any sugar in liquid form does not make you feel full the way solid food does. Therefore if weight is a problem for you, you should not take in calories in liquid form. Drink water or other zero-calorie beverages instead. More

Sunday, August 19, 2007

Spot Reduction Exercises Don't Work

Many people believe that if they do enough sit-ups they will get rid of belly fat, but your body does not work that way. Exercising a specific muscle does not get rid of more fat over that muscle in comparison to the rest of your body. If it did, tennis players would have less fat in their tennis arms, and this does not happen. Strength training strengthens weak muscles, but it cannot remove fat specifically over the strengthened muscle.

A recent study from the University of Connecticut showed that men who exercised one arm against heavy resistance for 12 weeks appeared to lose more fat in their exercised arm than their inactive one when fat was measured by a caliper that calculated skin thickness (Medicine & Science in Sports & Exercise, July 2007). However, when the same authors used an MRI machine to measure fat underneath the skin, there was no difference between the exercised and non- exercised arms.

When you take in more calories than your body burns, you store the extra calories as fat. More than half of the fat in your body is stored underneath your skin and over your muscles. Your stomach will look better when your belly muscles are strong, but sit-ups or crunches will not remove extra fat from your belly. The only way to lose fat from a specific part of your body is to lose weight overall. More on belly fat

Wednesday, August 15, 2007

Selenium May Increase Diabetes Risk

If you take selenium pills, you may be increasing your chances of developing diabetes, according to a report from the Nutritional Prevention of Cancer (NPC) trial (Annals of Internal Medicine, August 2007). This study is the largest and longest available experimental study of selenium supplements and was done by randomly selecting people for either placebos or selenium and then checking to see who develops diabetes.

In 1973, researchers showed that selenium protects against oxidative damage, chemical reactions that damage cells and shorten life. However, there is a narrow margin between getting enough selenium to keep you healthy and taking too much. High levels of selenium bind to and damage many essential body proteins. In the United States, dietary levels of selenium are high so there is little chances of developing selenium deficiency. Furthermore, selenium can be toxic to humans at low doses. Symptoms of poisoning include loss of hair and nails, tiredness, nerve or liver damage, and as shown in this study, diabetes. Selenium over-dosage cause oxidants to be formed in the body. They block the body's ability to respond to insulin and can even damage the insulin-producing cells in the pancreas. We do not know definitely that selenium causes diabetes, but until more data is available, most authorities recommend that people not take selenium supplements unless they have been tested and shown to have a selenium deficiency. Assess your risk for diabetes; weekly newsletter

Monday, August 13, 2007

Low Carb Diet Does Not Increase Endurance or Speed

Some athletes and exercisers believe that a low carbohydrate diet will increase their endurance and speed, but there is no evidence that it will. Runners get fuel for their muscles from fat and sugar in muscles, fat and sugar in the bloodstream and, to a lesser degree, from protein. The key to increasing endurance for racing is to store as much sugar in muscles before you race and keep it there as long as possible. Muscle sugar gives you the most energy for the least amount of oxygen.

Restricting carbohydrates does not stimulate muscles to store more sugar (Sports Medicine, April-May 2007). A low carbohydrate diet may impair performance if carried out for extended periods because a runner cannot train on a low- carbohydrate diet. If there are benefits from depleting muscles of their stored sugar supply, they probably come from the high- volume depletion workouts, not from the diet. To maximize stored muscle sugar, a runner should reduce his workouts for two to three days before a race. He or she should not restrict carbohydrates.

Another study from The University of Bern in Switzerland showed that a high carbohydrate, high-fat diet for three days before competition can help athletes store more fat in their muscles and use much more muscle fat for energy during exercise. Endurance-trained athletes exercised for three hours to empty sugar and fat reserves from their muscles. Then they ate a high-carbohydrate, low-fat diet for 2.5 days or the same diet with lots of added fat for the last 1.5 days. Athletes who ate the high-carbohydrate, high-fat diet stored 55 percent more fat in their muscles and used more than three times as much of that fat during exercise. More

Sunday, August 12, 2007

Athletes, exercisers and spectators: heed lightning warnings

People who are killed by lightning are often spectators or participants in sporting events. In the United States each year, lightning kills more than 70 people and injures more than 300 people, often permanently. Lightning strikes without warning, so sponsors of outdoor athletic events should have loudspeakers, sirens or horns to alert people to approaching electrical storms.

Water, metal and high objects attract lightning. When an electrical storm starts, try to enter a building or your automobile as quickly as possible. Get in your car, not near it. Standing near a car increases your risk of being struck by lightening because you are standing near metal. To avoid being near metal, get off your bike and away from it when you seek shelter. If you are on the golf course, get away from your golf clubs and carts and anything that contains metal.

If you are in an open field, you are the tallest object and therefore most likely to attract lightening. Standing makes you the tallest object, so if you cannot get to a sheltering building, go to a low spot and crouch down. Avoid being near the tallest object; do not stand under a single tree or by a pole. Standing under a tree that is shorter than other trees in the area is better. It is safer to be in a forest with many trees than to be under a single tree.

Don't stay in or near water. Just being near a lake, ocean or swimming pool increases your chances of being struck by lightning. Water sports such as swimming, fishing and boating increase your risk. Take the lifeguard's warnings or radio bulletins seriously, get out of the water and go to the nearest shelter. Fitness news

Wednesday, August 08, 2007

Napping Makes You Smarter

Two studies from Harvard show that napping make you smarter. I learned this for the first time when I was in the 7th grade. I would be in school from 8 AM to 3PM, go to work in the afternoon, and then come home at 6PM, eat supper and try to study and learn nothing. I would spend more time lying in bed thinking about studying than actually studying. So, in the seventh grade at age 12, I started a lifetime habit of sleeping every afternoon, even if I think that I don't need to sleep. I find that after just 30 to 60 minutes of sleep, I can think more clearly and do more work. If I don't sleep, I cannot write or think clearly.

Matthew Walker's study supports what I learned almost 60 year ago. He taught people to type a long list of words on a computer. He showed that those who were trained at night and were tested after a long night's sleep did far better than those who were trained in the morning and tested 12 hours later without sleeping. Thus, those who were tested after a night's sleep did much better than those who were tested after 12 hours being awake.

In the second study, Sara Mednick reported that she compared a person's ability to learn after no sleep, a 30-minute nap, or a 60 minute nap. Those who had a 30-minute nap did better than those who didn't nap, while those who took a 60-minute nap did far better than those who took only a 30-minute nap. When you start a nap, your eyes are kept still, called non-rapid-eye-movement sleep. You drop down from stage one sleep into a deeper stage two, then a deeper stage three, and then your eyes start to move rapidly back and forth. This is called Rapid Eye Movement sleep, also know as REM sleep. You learn best if you wake up right after non-rapid-eye-movement sleep (stage 2). And you get more non rapid eye movement sleep (stage 2) in a 60-minute nap than a 30-minute nap.

If you feel tired most afternoons, you are normal. In many parts of the world it is traditional to take an afternoon nap or siesta. Studies of office workers and school children show that people work best in the early morning. As the morning progresses, they lose their ability to concentrate, go out to lunch and function way below their capacity for the rest of the day. A study from the University of Pennsylvania Hospital shows that pilots, who sleep just 20 minutes during flights while their copilots take over, are more alert, attentive and responsive than those who don't nap.

It gets worse as you age. Older people fall asleep while you talk to them in the afternoon. An article in the medical journal, SLEEP, shows that a regular afternoon nap can help older people remain awake afternoon and evenings. They took a planned nap for 90 minutes between 1:30 and 3:00 in the afternoon. They were hooked up to special machines that showed that most slept for about one of the one and a half hours they lay in bed. These people had a remarkable improvement in their alertness in the afternoon and evening. They did not sleep as deeply at night and did awake a little earlier in the morning, but felt that the gain in alertness afternoons and evenings was far more important than this slight loss of sleep at night. Their sleep cycles however remained unchanged, so they still went to bed at their usual times.

Tiredness is a signal that your brain needs a rest. If you suffer from afternoon tiredness, find a quiet place to lie down during your lunch hour and take a nap. There is no data to support exercising when you feel tired because exercise does not perk you up. Recommendations to eat protein-rich foods and avoid carbohydrate ones are not based on solid data. Eating does not prevent afternoon tiredness and the drop in mental and physical performance. The only effective treatment for tiredness is rest. Set a radio to wake you to music, rather than a harsh sound that will jolt you, and expect to be far more productive than you were when you struggled to get through the afternoon and evenings without napping. Journal references; free fitness and health newsletter

Tuesday, August 07, 2007

Fasting Triglycerides Test for Heart Attack Risk Unreliable

For more than 50 years doctors have used fasting blood triglyceride levels to predict a future heart attack, but now two studies in the Journal of the American Medical Association show that non-fasting blood triglyceride levels are far more dependable (July 18, 2007). When your blood sugar rises too high after eating, your pancreas releases huge amounts of insulin. Insulin converts sugar to triglycerides. Triglycerides are therefore a marker for a high blood sugar levels that damage arteries to cause heart attacks. More than 75 percent of diabetics die of heart disease.

Many people have normal blood sugar and triglyceride levels after an overnight fast, but have their blood sugar levels rise too high after eating and therefore have a high rise in triglycerides only after eating. This means that having normal triglycerides after fasting does not rule out high risk for a heart attack. High triglycerides after eating shows that you have high blood sugar levels and should restrict foods and beverages made with sugar, flour or other refined carbohydrates, the foods that cause the highest rise in blood sugar.

You can tell if you are at high risk for diabetes if you store fat primarily in your belly. Pinch your belly; if you can pinch an inch, you are at increased risk and should get a blood test called HBA1C. Having high blood levels of triglycerides and low levels of the good HDL cholesterol that helps prevent heart attacks also increases your risk for diabetes. When you eat sugar or flour, your blood sugar rises too high. This causes your pancreas to release insulin that converts sugar to triglycerides, which are poured into your bloodstream. Then the good HDL cholesterol tries to remove triglycerides by carrying them back into the liver, so having high blood levels of triglycerides and low blood levels of the good HDL cholesterol are both individual risk factors for diabetes. More on pre-diabetes; more on insulin resistance

Sunday, August 05, 2007

Muscle Sugar More Important Than Fluid for Endurance

How fast you can move and how long you can exercise intensely depends on the amount of sugar (glycogen) stored in your muscles. The same rule applies in all sports: when muscles run out of their stored sugar supply, they require more oxygen and you have to slow down.

Fluid is less important than muscle sugar because dehydration will not cause you to slow down until your blood volume is reduced. As you lose fluid from sweating, interstitial fluid stored around cells is released into the blood to maintain blood volume. When you compete is sports at a very high intensity, your muscles run out for stored sugar long before your blood volume is reduced, and you slow down from lack of muscle sugar before you slow down from reduced blood volume (Sports Medicine, April- May 2007).

Fuel for muscles comes from sugar and fat stored in muscles, sugar and fat in the bloodstream and, to a lesser degree, protein. When you start to exercise intensely, more than 50 percent of your energy comes from sugar stored in muscles. Two hours later, most of the sugar stored in muscles is used up and less than 10 percent of energy comes from that source. If you do not supply extra sugar during exercise so that your muscles will use less of their stored sugar, muscles run out of glycogen and your performance will suffer. More on hyponatremia

Wednesday, August 01, 2007

Low vitamin D prevents insulin response; sunlight may not be enough

A recent study from the University of Wisconsin Osteoporosis Clinical Research Program in Madison, showed that some people have very low levels of vitamin D in spite of getting a lot of sunlight where they live in sun-drenched Hawaii (Journal of Clinical Endocrinology & Metabolism, June 2007).
The 93 participants in the study averaged 22.4 hours per week outside without sun screen. In spite of abundant sun exposure, 51 percent had low vitamin D levels.

Many people think of vitamin D as the vitamin that helps to prevent rickets, a disease characterized by weak bones that break easily. However, vitamin D does much more than that. It is necessary for your immune system to search out and destroy invading bacteria, viruses and even cancer cells. Recent studies show that lack of vitamin D prevents your body from responding to insulin adequately. The Third National Health and Nutrition Examination Survey shows that having low levels of vitamin D increases risk for high blood pressure, obesity, diabetes and having high blood levels of triglycerides (Archives of Internal Medicine, Volume 167, 2007). Researchers at Tufts University in Massachusetts showed that obesity increases a person's chances of having low vitamin D levels (Journal of Clinical Endocrinology & Metabolism, May 2007). A possible explanation is that fat sops up the available vitamin D so that it is not readily available to be used by the body.

Most people do not get adequate amounts of vitamin D from the food that they eat. They must depend on sunlight. People with dark skin require more sunlight to meet their needs for that vitamin, which could explain the increased risk for diabetes in dark-skinned people who live far from the equator. Calcium blocks the activation of vitamin D so people who take calcium supplements need to get extra sunlight or take vitamin D supplements. The large amount of calcium in milk can lower vitamin D levels even when the milk is fortified with the vitamin.

Vitamin D can be made in the skin when it is exposed to ultraviolet light from the sun. Then the liver converts vitamin D to an active hormone form called 25 hydroxy vitamin D. Then your kidneys convert this hormone to a more active di-hydroxy vitamin D. So you get that vitamin from your skin, liver and kidneys, and lack of sunlight and liver or kidney diseases can cause a deficiency. Now we learn that some people can be deficient even with adequate sunlight exposure and normal kidneys and livers. The only way to find if you are deficient of vitamin D is to get a blood test called 1,25 diyhxdroxy-vitamin D.