DEAR DR. DONOHUE: Last year my son suffered a concussion during the last football game of the season. He wasn’t knocked out, but he was groggy for a whole day and had a headache for three days. Our family doctor examined him, and so did a neurologist. Neither found anything wrong.

He wants to play football again this year. I am dead set against it; my husband is for it. Should he be allowed to play? What should we look for if he does play? – B.Z.

ANSWER: A concussion does not require that a person lose consciousness. It’s an interruption of normal brain function. Concussions come in varying degrees of seriousness, but none can be ignored.

The least dangerous is a grade 1 concussion, an injury that causes mild, transient confusion. The person might be unsteady. Often he or she can’t remember what caused the injury and finds it hard to retain information immediately following the accident. The player can also be unable to carry out specific instructions. All these symptoms last less than 15 minutes.

A concussion a grade 2 when the above symptoms last for more than 15 minutes.

A grade 3 concussion is a loss of consciousness, even for brief periods of time.

What makes any grade of concussion a serious matter is the fact that the brain is more vulnerable to a second concussion until it has fully recovered. Full recovery can take up to seven days.

Your son can safely play football this year. After even severe concussions, most have no impairment within 90 days, and your son is well past that milestone. That is not true of all concussions and is often not true after a second one.

If your son sustains even a mild concussion this year, he should not return to play for a full week, and perhaps he should be examined by the family doctor before he resumes play.

DEAR DR. DONOHUE: I try to get in 30 minutes of walking every day. Most of the time I can’t. I am a busy mom and have to be in many different places during the day. I can manage 10-minute walks. If I take three of those, would I get the same benefit as a 30-minute walk? I want to lose weight, and walking definitely helps me. – K.D.

ANSWER: Three 10-minute walking sessions are as beneficial as one uninterrupted 30-minute session.

This has been proven with untrained men between the ages of 40 and 49. They were divided into two groups. One walked for 30 minutes straight. The other group had three 10-minute walking sessions.

Both groups burned the same number of calories, about 280. I am sure this applies to women as well as men.

If you follow this program for a full year, walking every day, you can anticipate a weight loss of 25 to 30 pounds.

Ten minutes is the minimal time interval. Less than that does not provide as much benefit or burn as many calories, even if the total amount of time adds up to 30 minutes.

DEAR DR. DONOHUE: I am 18 and into weightlifting big-time. I have a friend who has diabetes. He is a weightlifter too. He says he read that injecting insulin builds muscles quickly, and he’s offered to share his insulin with me. What do you think of this? – M.R.

ANSWER: I think the idea is dangerous.

There is evidence that insulin slows muscle protein breakdown and increases muscle protein synthesis. It also packs muscle cells with glycogen (muscle sugar). The same effect comes from the body’s own naturally made insulin. Diabetics need injected insulin to replace what their bodies no longer make.

The use of insulin by someone who does not need it can drop blood sugar to very low and very unsafe levels. Don’t even think about doing this.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475.

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