Fluid Rules for Cyclists

Exercise nutrition is not rocket science, but it isn’t finger painting either. A little knowledge is required to do fuel your rides properly. Many cyclists do not fuel properly, and it makes a difference. Here are the facts and guidelines that every cyclist should know.

The two main purposes of exercise nutrition are hydration and energy provision.

Perspiration is the body’s cooling mechanism. Sweating keeps the body’s core temperature from rising. Sweat contains water and electrolyte minerals. The more water and electrolytes the body loses, the less efficient this cooling mechanism becomes. At the same time, cardiac and motor signaling efficiency decrease and the risk of muscle cramping increases.

As little as 1% loss of body fluids can negatively impact endurance performance. For a 160-lb. cyclist, this equates to about 1.5 lbs. of fluid loss.

Typically, cyclists sweat at the rate of 900-1,200 ml per hour, but actual sweat rates depend on weight, intensity, air temperature, and genetic factors. Cyclists should consume fluids containing water and electrolytes (sodium, chloride, potassium, and magnesium) at a similar rate. Studies show that doing so has a strong, positive impact on performance.

Carbohydrate is the primary source of energy for muscle contractions during cycling. Typically, cyclists burn at least 200 grams of carbohydrate an hour while riding. The body can only store enough carbohydrate to fuel three or four hours of moderate-intensity riding.

Studies have shown that consuming carbohydrate during exercise lasting 60 minutes or more can greatly enhance endurance performance. However, the average cyclist cannot absorb more than 70 to 80 grams of carbohydrate per hour. You should try to get about this amount.

It is important to get your nutrition in an easily absorbed form during exercise. Most sports drinks are formulated to provide water, electrolytes, and carbohydrate in the right balance for fast absorption.

Insulin is a hormone that is responsible for transporting carbohydrate into the muscle cells. The pancreases releases insulin automatically in response to rising glucose levels in the blood. Protein also stimulates insulin release. Research has shown that the addition of protein to a sports drink increases insulin release and results in faster deliver of carbohydrate to the muscle cells. This allows the muscles to conserve their stored carbohydrate and prolongs endurance.

Too much protein in a sports drink would slow stomach emptying and sabotage the insulin effect. The ideal ratio of carbohydrate and protein in a sports drink is 4:1. This ratio maximizes insulin release without slowing stomach emptying.

Many cyclists are unaware that protein is also broken down for energy during exercise. The longer exercise lasts and the lower the body’s carbohydrate supply gets, the more protein is used. After 90 minutes of vigorous activity, as much as 15% of the muscles’ energy comes from protein. Most of this protein comes from the breakdown of muscle cells.

Consuming protein during exercise accelerates muscle protein rebuilding after exercise and may also reduce muscle protein breakdown during exercise.

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