Dr. James Allen Watrous, Ph.D.

Dehydration occurs to everyone all the time for all levels of activity, including breathing.  Even when you sleep you dehydrate.  When riding a bicycle, the water loss is accelerated.  The average 160 lb. person will require one tall water bottle (26 oz.) per hour under normal conditions day or night.  If the climate is hotter or dryer, then the water needs can increase to as much as two tall water bottles per hour.  Mountain climates are generally dryer than lower elevations.  Thus, your water loss will be greater in the mountains, even at cooler temperatures.

All riders must LEARN to drink frequently.  A ten minute interval is about right.  REMEMBER - WHEN YOU BECOME THIRSTY, YOU ARE AN HOUR LATE AND A QUART LOW!  The human body mechanisms generate warning signs in desperation.  That is, the thirsty sensation is like the red oil light coming on in a car.  Take Action Now.

Even minor dehydration will reduce your fun and performance.  Remember dehydration is very dangerous!  Once you have gone beyond being thirsty and beyond sweating, you are entering a critical situation.  The body is not providing you any warnings and you could simply lose consciousness while riding.  This is not good!

So choose to drink often with sufficient quantities.  Since most bicyclists are not in the habit of drinking sufficient quantities frequently, you may psychologically convince yourself that you do not need this water.  If you allow a mental emotion to make your choices for you, you are ignoring the reality of the human body mechanism and its physical needs.  If you choose not to drink adequately, then you risk a severe penalty of dehydration and hospitalization.

Human Water Needs While Bicycling

Note: water with small percentages (4 to 7%) of carbohydrates and adequate amounts of electrolytes will increase the water absorption by the body in the small intestine and replace the electrolytes lost in sweating.



Water Need Range

per Hour

Number of Water Bottles

120 lb

16 oz. to 40 oz.

1 to 2 1/2 regular

160 lb

26 oz. to 65 oz.

1 to 2 1/2 tall

200 lb

36 oz. to 88 oz.

1 1/2 to 3 1/2 tall

Water bottles that allow you to see the water level are best for maintaining your hydration.

Regular Water Bottle = 16 oz or 1/2 liter.

Tall Water Bottle = 26 oz or 3/4 liter.

A Tall Water Bottle equals about 1.7 pounds or 0.77 kilograms.

A lose of 2 pounds of body weight do to dehydration [more than one tall water bottle] equals a performance lose of 1 to 3 percent depending on total body weight.  A lose of 4 pounds of body weight do to dehydration [two and half tall water bottles] equals a performance lose of 3 to 7 percent depending on total body weight.  As you approach 6 pounds of body weight lose do to dehydration [three and half tall water bottles], your performance lose can jump to 10 to 20 percent.  Clearly, as dehydration occurs, your fun decreases quickly.

When dehydration occurs, the balance between body functions, synchronization of body functions and electrolyte balances begin to change and become disorganized.  Your performance will decrease regardless of your fitness level (from beginner to pro-athlete).

Copyright, 2017, 1981 to 2017. Watrous' Cycling Enterprises