Bone Density Does Not Necessarily Measure Bone Strength

The greater the force you put on your bones during exercise, the stronger they become. Researchers at the University of Missouri in Columbia showed that recreational runners have denser bones than cyclists (Journal of Metabolism, February 2008). Another study from Université de St-Etienne in France show that youth soccer players have an increase in bone density over three years of playing high level soccer (Joint Bone Spine, January 2008). They failed to show that the soccer players had denser bones than their classmates, yet their intuition told them that heavy forces on bones while playing soccer must strengthen bones, so they stated that "The yearly gain in bone density is greater in soccer players than in controls."

These studies and many others comparing various sports measure bone density, not bone strength. The only way to measure bone strength is to see how much force it takes to break them. Needless to say, nobody is doing these studies in humans. So scientists use bone density, which can be measured, as a substitute for measuring bone strength. Nobody has shown that bone density determines bone strength. For example, birds have bones that are not dense because they need a low weight to fly effectively. Yet their bones are very strong. I think that, in the future, methods will be developed to determine bone strength and they will show that measuring bone density is, at best, a crude measure of whether a person is likely to break his or her bones. More

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Sexual Activity or Exercise: Which Stresses the Heart More?

The stress on the heart from making love is relatively insignificant, compared to that caused by exercising, according to a study from the University of Medicine and Dentistry of New Jersey in New Brunswick. Nineteen men and thirteen women performed a maximal-effort stress test (exercising vigorously on a treadmill) followed by home-monitored sexual activity using heart rate and blood pressure recording devices. During sexual activity the men had maximum heart rates 28 percent lower than during exercise, and systolic blood pressure 20 percent lower. In the women the heart rate was 36 percent lower and blood pressure 25 percent lower. Journal reference

The duration of treadmill exercise slowed by nine seconds for each additional year of age, and duration of sexual activity slowed by one minute for each year of age. How long they could make love correlated with how long they could run on a treadmill. For each additional minute on the treadmill, the person could make love for an additional 2.3 minutes. More

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Competitive Sports for Children?

Today, if you want your children to be champion athletes, they need to start training at a young age and play their sport 12 months a year. So naturally you want to know if heavy athletic training before and during the period of rapid growth in children will harm then in any way. The most common concern is whether heavy training will make them shorter as adults or damage the growth plates in their bones. Researchers at the University of Saskatchewan studied young gymnasts, swimmers and tennis players and showed that participation in these sports does not shorten their adult height. Furthermore it did not affect the age when they entered puberty. Journal reference

The biggest concern about starting training this early is not physical, it's whether you will destroy a child's desire to play that sport after you have taken away his or her childhood. Children as young as five years old are shipped off to Florida where they have private tutors and play tennis for several hours a day. Young football players are encouraged to take supplements. Gymnasts work out for six hours a day and are told to restrict calories. Try not to be one of those parents or coaches who place athletic training above the child's best interests.

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Weight Gained When You Stop Exercising May Be Hard to Lose

If you want to use exercise to help control your weight, don't stop. Paul Williams of the University of California at Berkeley showed that interrupting an exercise program can cause you to gain weight that won't come off easily even after you resume training (Medicine & Science in Sports & Exercise, February 2008).

Williams compared 17,280 men and 5,970 women who decreased their running distances with 4,632 men and 1,953 women who increased their running distances over an eight year period. He found that runners who decreased their distance from five to zero miles per week gained four times as much weight as those who decreased their distance from 25 to 20 miles per week. He also found that people who started running after an exercise layoff didn't lose weight until their mileage exceeded 20 miles per week in men, and 10 miles per week in women.

The people in the lower mileage groups were not able to lose the weight gained during time off if they just resumed the same exercise regimen. This study explains why exercise programs designed to prevent obesity may fall short if the exercise is irregular, seasonal, or often interrupted. "Many scientists attribute the obesity epidemic to excess calories rather than [lack of] exercise, because dieting has been shown to produce more weight loss than exercise," says Williams. "My findings suggest that calorie intake and body weight may be self regulating in active individuals." More on exercise and weight control

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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

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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

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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

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