Stretching aids athletics, but not muscle strength


Lots of people think that stretching before exercise prevents injuries. There is no evidence that it does, but there is evidence that stretching can help to make you a better athlete.

Every time you exercise, you injure some of your muscle fibers. They shorten when they heal, and short, tight muscles are more likely to tear. Muscles and tendons tear when the force on them is greater than their inherent strength. Stretching does not make muscles stronger. Heavy resistance training is what strengthens muscles and makes them less likely to tear.

If you compete in sports, stretching may improve your performance. Stretching makes your muscles and tendons longer, and longer muscles generate a greater torque around a joint. The increased force can help you to lift heavier weights, run faster, jump higher and throw further.

If you decide to stretch, do it after you warm up or after you exercise. Resting muscles have a temperature of about 98 degrees Fahrenheit. When you exercise enough to start to sweat, your exercising muscle temperature is more than 101 degrees. The increased temperature makes the muscles and tendons more pliable and less likely to tear.

Do not stretch further than you can hold for a few seconds. Several studies show that bouncing can give you a longer stretch, but it is also more likely to tear your muscles. If you're over 50, you need to be particularly careful when you stretch. Aging robs muscles of their normal springiness and makes them tear more easily.

Q: Will vitamin pills help combat stress?

A: There is no evidence that stress increases your need for vitamins or that taking vitamins will help you to handle stress. Most vitamins are parts of chemicals called enzymes that cause reactions to proceed in your body. When chemical A is converted to chemical B and releases energy, a vitamin starts the reaction. Since enzymes only start chemical reactions and are not used up by them, they can be used over and over again and only minuscule amounts are needed from your diet.

One of the largest drug companies in the world advertised that their vitamin pills help relieve stress from the "complications of everyday life." They further claimed that taking their vitamins would reduce the effects of psychological stress. They were forced to stop making these claims.

Q: Is it true that the food you eat at night is more fattening than what you eat in the morning?

A: Yes. When you eat more food than your body needs, the extra calories are converted to fat by your liver. If you eat and then exercise immediately afterward, there usually are no extra calories and you store no fat. However, when you are inactive, you burn fewer calories and the extra calories are converted to fat. If you want to lose weight, pick a lower body exercise such as dancing, walking or cycling and alternate it with an upper body sport such as rowing or swimming, and heed the latest word from the scientific community to eat like a king for breakfast, eat like a prince for lunch and eat like a pauper for supper.

Dr. Mirkin is a practicing physician in Silver Spring specializing in sports medicine and nutrition.

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