Water Intake During Exercise

Coach Paul Greer of the San Diego Track Club has been helping runners train for the Rock ‘n’ Roll San Diego Marathon & 1/2 for 20 years running! In this series, we’ll feature tips, workouts and programs, courtesy of Coach, that will help you conquer your first or 100th marathon!

The body’s need for water is second in importance only to its need for oxygen. Adult body weight is approximately 55 – 65% water. A 10% loss poses significant health risks, and a 20% loss may result in death.

Water plays an essential role in the human energy system. The more we expend, the more we need. During running, only 25% of the energy generated by the body is turned into mechanical work. The balance is actually turned into heat. The heat must be removed by sweating to avoid dangerous increases in body temperature.

During intense running, the body can lose up to two liters of water as sweat. A marathon runner can actually lose 13 lbs of body weight in the form of water during a race. Dehydration due to water loss during running can have a significant effect on the body’s performance. When water is drawn away from the working muscles, blood volume is decreased. The heart must pump harder to supply the same amount of energy.

Here are the following suggestions to ensure that your body has adequate water while running:

  • Drink 8 – 10 ounce glasses daily.
  • Start drinking before you feel thirsty since during activity the body loses water faster in sweat than it can absorb into the digestive system.
  • Use water to cool your skin during running.
  • Don’t count on thirst as an accurate guide to your water needs. You will quench your thirst long before you replenish your body supply.
  • Finally, do not try to lose weight by failing to replace water lost during your running activity.

About Coach Paul Greer

Coach Paul Greer is Professor in Health and Exercise Science at San Diego City College and has a Master’s Degree in Exercise Science and 32 years coaching experience. Greer ran the mile in under four minutes (3:59.79) and was a 1992 U.S. Olympic Trials qualifier at 1500 meters with a 3:39.05. In addition to teaching at San Diego City, Greer also coaches for the San Diego Track Club; the largest running club in San Diego. He works with over 500 runners and is the Director for the Rockin N Runnin full and half marathon training program preparing athletes every year for San Diego’s Rock N Roll marathon/half marathon in June. Greer’s workouts cater for runners of all ages and abilities and he provides training schedules to his athletes on an individual basis.

Coach Paul Greer was featured in The Game Changer, the debut episode of Milestones, a video series that celebrates and commemorate the Rock ‘n’ Roll Marathon Series history.