Is drinking only when thirsty enough to stay hydrated while cycling?

QUESTION: I’m a recreational cyclist. I always take a water bottle with me on rides, but I only drink from it when I feel thirsty. I avoid sports drinks because they sometimes upset my stomach. Otherwise, I feel OK when sticking with plain water. But some friends who ride tell me I should be drinking on a schedule, whether I feel thirsty or not and that some of what I drink should include electrolytes. Are they right, and if so, why? —Aaron J.

RBR’S STAN PURDUM REPLIES: Your friends are likely referring to the fact that it’s easy when exercising to become dehydrated, since we all lose body water volume simply by sweating and breathing. And there are studies, such as this one, that show that drinking on a schedule leads to better cycling performance. At the same time, some authorities say that mild dehydration does not impair exercise.

Where there’s no argument is in competitive cycling. Among the factors that have led to improved performance are programs of prescribed eating and drinking while on the bike. Recreational cyclists can make some gains by adopting their own programs of on-bike consumption, but with professional cyclists, the food and fluid intake is part of a larger focus on menu and diet while off the bike as well.

If you feel good and are happy with your performance on the bike, there is no reason to change your approach. What’s more, some authorities say that for most people, drinking when thirsty is typically enough to stop cyclists from losing more than 2% of their body weight in water (the level of loss at which some experts say dehydration becomes detrimental).

One addition you might consider, however, especially in hot weather when you are sweating more, is to consume some salty snacks, such as pretzels or corn chips and some carbs from an energy bar or, my preference, fig bars.

You did not mention how long you typically ride, but time on the bike can also affect how much and how often you need to drink. If you’re well hydrated before you start riding, you often can ride for an hour in moderate weather without needing to drink more. On longer rides, many nutritionists recommend you drink the equivalent of a full water bottle full per hour, which is probably good as rule of thumb, but I often find it too much for me.

Unless, that is, the circumstances of my ride change. Once when riding on a bike tour across America, I had to do the trip in segments over time instead of in a single long crossing. At one point, after some months back home, I resumed my ride in Colorado, climbing to 11,500 feet going over the Continental Divide the first day back. I expected some breathing problems at that high altitude, but what I hadn’t anticipated was how that altitude would affect my hydration. Long story short, even after drinking more than usual, I became dehydrated and continued to feel lousy the next day, and then I got worse. I finally had to stop at the home of strangers and ask for help getting to an emergency room.

Here’s how I described the ER visit in my book about my coast-to-coast ride, Roll Around Heaven All Day:

The emergency room modeled efficiency. A nurse interviewed me within two minutes of my entry, a doctor checked me over three minutes later, and five minutes after that the first of three liters of intravenous fluid pulsed into my arm. “Chronic dehydration,” the doctor diagnosed. “It happens easily at high, dry altitudes. There’s not enough air pressure to keep the moisture in your body. You need to drink lots more water than usual when you’re working as hard as you were at that height.”

Later, after seeing my blood test results, she added, “You’re severely dehydrated. Your enzymes and blood sugar are all out of whack, and your muscles were even starting to break down.”

Five hours later, after finally squeezing out enough urine to prove that my functions were returning, I was released.

The strangers, who proved to be a family of good Samaritans, put me up for the night, firmly refusing my attempt to pay for their help. I continued my trip the next day. Later in my journey, in Kansas, I rode another hot stretch, not at high altitude this time, but ran out of water. I started to experience some nausea, similar to what I’d had in Colorado, but I recalled that the printed discharge instructions from the emergency room described a “fluid replacement mixture” I could concoct myself: one teaspoon of sugar and one-half teaspoon of salt dissolved in one pint of water. In a Kansas convenience store, I used a soft drink cup and the sugar and salt packets to make this cocktail. After drinking it, I felt somewhat better, so I mixed and swallowed another. Almost immediately all the nausea fled.

So do take hydration seriously.

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Stan Purdum has ridden several long-distance bike trips, including an across-America ride recounted in his book Roll Around Heaven All Day, and a trek on U.S. 62, from Niagara Falls, New York, to El Paso, Texas, the subject of his book Playing in Traffic. Stan, a freelance writer and editor, lives in Ohio. See more at www.StanPurdum.com.