What to drink when exercising in the heat


DEAR DR. DONOHUE: I am taking my two teenage boys backpacking in the Southwest this August. It will be hot and dry, and I am preparing for those conditions.

I need some guidance on what fluids to drink. I was taught that drinking plain water is the best way to stay hydrated. My older son says his class was told not to drink plain water, because it could cause brain damage. What is this all about? – F.W.

It’s all about becoming sodium-depleted and having the brain swell as a result. The condition is hyponatremia.It used to be taught that, when exercising in hot weather, people should guzzle water at every opportunity, even when they don’t feel thirsty.

That can be dangerous if the exercise lasts for hours and hours and if the only liquid drunk is water.

Too much water dilutes body sodium. That, in turn, can cause brain swelling and, in the extreme, death. Up-to-date advice is to let thirst be a rough guide for how much liquid you drink.

If people are engaged in prolonged exercise, it is good to include some salt in the program.

Half a teaspoon of salt and half a teaspoon of baking soda (sodium bicarbonate) in a quart of water can keep body sodium levels from dropping. For you and your sons, it would be advisable to salt your food and to eat some salty snacks – another way to ensure body sodium doesn’t bottom out.Hyponatremia is uncommon. Dehydration is common.

For most, drinking water as a replacement fluid in hot weather is fine. It’s not going to lead to a dangerous drop in body sodium.

Only those who lose lots of sweat for long periods of time run the risk of hyponatremia by drinking pure water.This is advice that doesn’t apply only to athletes or backpackers. It applies to all those who are out working in hot weather and sweating up a storm.

DEAR DR. DONOHUE: At 73, my maximum heart rate is calculated to be 147 beats a minute. I have been told that to give the heart proper exercise, you should maintain a heart rate of 60 percent of the maximum for at least 20 minutes. For me that would be a heart rate of 88 beats a minute. I work out in a gym with weights, and I use a treadmill. If I average 94 beats a minute for an hour or more, am I accomplishing the same thing? – G.B.

I’m not sure I understand your question. Any heart-rate increase over a person’s resting heart rate is good for that person and that person’s heart.

The heart-rate rule you are using is the one that says maximum heart rate is obtained by deducting age from 220 – your 147.

A beginner gets adequate exercise by taking 60 percent of the maximum heart rate as a target rate – for you, that would be 88, not exactly a high heartbeat.

With conditioning, a person should gradually try to get his or her heart beating to 80 percent of the maximum rate – for you, that would be 118.

Please note: These rules are made up. There’s not a whole lot of science behind them. To know if your exercise is giving your heart the stress it needs, all you need is your evaluation of the workout. If you feel you’re exercising moderately hard, that’s as good as any heart rate rule.

You shouldn’t be panting for breath during or at the end of your exercise, you shouldn’t be wiped out by it, and you should feel invigorated by it.

Your current exercise accomplishes all that you want and then some.

People at older ages ought to seek their physician’s approval for any exercise program.

DEAR DR. DONOHUE: I have lost 78 pounds. I exercise three times a week for 30 minutes each time. How can I get rid of my hips and stomach? – J.L.

You’ve done wonders. If it’s fat that makes your hips prominent, you need to lose some more pounds. Fat cannot be selectively removed from a particular area by any exercise. It goes equally from all fat depots.

Your stomach might be protruding because of posture. Stand with your back against a wall. If you can fit your fist between your lower back and the wall, your back curves in too far. If you flatten the curve, your stomach will be drawn in.

DEAR DR. DONOHUE: Nowadays there is such a to-do about gluten sensitivity and celiac disease. Which comes first? – F.G.

Gluten sensitivity and celiac disease are different names for the same condition. Gluten is a protein found in wheat, barley and rye. People with a sensitivity to gluten develop an inability to absorb nutrients, causing diarrhea and weight loss. Gluten acts like a poison to their digestive tracts. Treatment is avoidance of those grains and gluten.

You can call the illness celiac disease, gluten sensitivity, gluten enteropathy or sprue – whichever strikes your fancy.

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. Readers may also order health newsletters from www.rbmamall.com