Do I need to Fuel for an Event Less Than One Hour?
Jeffrey Rocco, M.D.

The short answer is no, but depending on your pre-race hydration and glycogen stores, you might need to fuel during an event lasting an hour or less. All athletes would like to perform at their personal best, however, your best may be compromised by dehydration, lack of muscle glycogen, or electrolyte imbalances.

Fluid and electrolytes are lost primarily through sweat. Sweating is your body’s mechanism to dissipate heat generated by working muscles. Higher temperatures and more intense exercise will result in higher core temperatures, and hence, more sweat and more fluids lost. Athletic performance begins to suffer when fluid losses exceed 2% of body weight. Rates of fluid loss can vary from 500 to 3000ml per hour; this is roughly between 1 and 6 pounds. For example, if a 150 lb. athlete loses 1500ml of sweat during an hour of exercise, that would be at the 2% threshold, and their performance will likely suffer.

You can determine your own sweat rate with a simple test during a one hour workout. The test should be performed under similar conditions to your anticipated event. Weigh yourself nude before exercising. Workout for one hour. Consume as much fluid as you want during exercise and record carefully the amount consumed. At the end of your workout, weigh yourself again. Subtract post workout weight from the pre workout weight and add the fluids (16 oz. per pound) consumed during the workout. This is your sweat rate per hour.

Sweat rate=Weight Before -Weight After + Fluids consumed

If your sweat rate approaches 2% of your body weight for the anticipated duration of your event, your will probably need hydration during the event. This assumes proper hydration prior to the start of the event. The American College of Sports Medicine has released guidelines for proper hydration (1). Fluids should be consumed before the event, depending on the weight of the athlete:

The beverage consumed should contain carbohydrates and electrolytes. EFS by First Endurance is an optimal choice for hydration and contains electrolytes in significant enough quantity to replace those lost during exercise.

Carbohydrate consumption needs to be considered in addition to fluid and electrolyte losses. As the intensity of exercise increases, the proportion of carbohydrates burned will increase. Calorie consumption will also increase as the size of the athlete increases. Approximately 1500 calories of energy are stored in the form of muscle glycogen. Extremely intense exercise (“race pace”) may deplete these stores entirely over the course of an hour. It is important to maximize glycogen stores and start the event with a full tank. Replenishing glycogen stores immediately following exercise can help to keep the tank full and ready for the next event.

Consuming carbohydrates during exercise can help to prevent the “bonk” that occurs when glycogen stores have been depleted. A solution containing 6-8% high glycemic index carbohydrates has been shown to be optimal for gastric (stomach) emptying and absorption (3). Even a carbohydrate mouth rinse that isn’t actually consumed has been shown to improve performance during exercise during a one hour time trial (2). With easily digested carbohydrates from multiple sources, most athletes can safely consume and metabolize between 45g and 90g of carbohydrates per hour. For example 24 oz. of EFS contains 48g of carbohydrates in addition to adequate amounts of electrolytes necessary to maintain performance.

To summarize: It is important to start every race, regardless of length, with energy and hydration reserves topped off. Races less than half an hour probably don’t require additional fuel during the race. As the race length approaches one hour, fuelling with fluid, carbohydrates and electrolytes will improve performance.

References:

3 Guezennec CY, Satabin C, Duforez F, Koziet J, Antoine JM (1993). The role of type and structure of complex carbohydrates response to physical exercise. Int. J. Sports Med. 14:224-231.