Dripping in Sweat

You're puffing along on the treadmill at an even pace with the guy to the right and left.  You are drenched in sweat.  The guy on your right has a small stain on his shirt and the guy on the left strides with barely a bead of sweat on his brow.  No two people produce the same amount of sweat even doing the same workload. Some people can workout on their lunch break and go right back to their desks just as fresh as before and others would be offensive unless they hit the shower.  While you may not think of it this way, sweat is good for your body. How much we sweat is determined by a number of factors. 

 
What is sweat? 
 
Sweating is the body's most effective way of cooling itself. During exercise or when exposed to a hot environment, heat is released by the body, and body temperature rises. The rise in body temperature causes an increase in sweating and blood flow to the skin.  As a result, heat is removed by the evaporation of sweat from the skin, radiated from the body to the cooler surroundings, and is lost by convection to moving air.
 
What causes sweat?
 
The human body is approximately 55 to 65 percent fluid. We lose water from our body in one of four ways: perspiration, urination, respiration and leaky skin. Respiration and leaky skin produce what is known as insensible water loss, which amounts to approximately 500 milliliters per day. However, adults need to replace anywhere from 2 to 10 liters of water each day, depending upon genetics, fitness level, exercise intensity, environmental conditions (temperature, humidity), clothing, hydration and age. Water lost to perspiration occurs during exercise (or sometimes in response to stress) or in hot, humid conditions. 
 
What determines how much an individual sweats?
 
Why some people sweat more than others is determined by the number of sweat glands they possess. Humans are born with approximately 2.4 million sweat glands.  While even newborns sweat, the number of active sweat glands increases once individuals reach puberty. The most concentrated area of sweat glands is on the bottom of the feet, while the least concentrated area of sweat glands is on the back. While women have more sweat glands than men, men's are actually more active, and hence, they tend to sweat more. Other than genetics, fitness level appears to play the most active role in how much individuals sweat. Exercise intensity plays a role: The harder your body works, the higher the body temperate and the greater the sweat loss; however, as individuals increase their fitness levels, they become better sweaters.  Fitter individuals sweat sooner and sweat more. In addition, the body more easily adapts to exercise in warmer temperatures by sweating more. Some studies have shown that elite athletes can raise their metabolisms and begin sweating in the time period prior to beginning exerciser. Their bodies become so efficient that they begin warming up in preparation for exercise. Other factors that influence how much individuals sweat include the environment and clothing. Higher temperatures cause individuals to sweat more quickly and to lose more fluids through sweat. In addition, if humidity levels are high, it's more difficult for sweat to evaporate, which affects a person's ability to cool off. Wearing fewer and loose-fitting clothes helps to promote heat loss.
 
Replacing sweat loss -
 
The amount of water lost by the body through sweat is enormous. People typically fall into three ranges: low, average or high sweat loss. Those who fall into the low sweat-loss range lose up to 1 quart of sweat per hour during exercise; those in the average range lose up to 2 quarts of sweat per hour during exercise; and those in the high range lose up to 3 quarts. Those who fall into the high range are at greater risk of dehydration, fatigue, cramps, heat intolerance and slow recovery after exercise. The key to replacing water lost through sweat is to know your sweat rate.  Weigh yourself naked pre- and post-exercise, and then adjust for deficits. For instance, an individual weighing 152 pounds prior to exercising, and 150 pounds after exercise would need to replace 2 pounds of water weight, or 32 ounces of water (152 - 150 = 2 lb. = 32 oz.). It's important to note that sweat is not just made up of water. Sweat is also composed of ammonia, calcium, chloride, copper, creatine, iodine, iron, lactic acid, magnesium, manganese, phosphorus, potassium, sodium, urea and uric acid. Sodium and chloride are the predominate nutrients in sweat, with potassium, calcium and magnesium following, and all other nutrients accounting for trace amounts. Each individual loses sweat sodium in different concentrations; some people's sweat contains high levels of sodium, while others have low or average levels. Those who lose high levels of sweat sodium are at high risk of muscle cramps. Exercisers who are cramp-prone usually have or display some obvious signs, include a history of heat cramps, avoiding salt, inability to acclimatize, profuse sweating, prone to dehydration, or have legs and arms caked in salt after exercise. A drink high in sodium and potassium is recommended for these individuals post-exercise.

 
What's the Best Way to Replace Sweat?
 
The following recommendations are given as the best way to replace sweat:  Consume 20 ounces of water in the 60 minutes prior to exercise  Drink 1 cup of fluid every 15 minutes during exercise.  Drink 16 ounces per pound of lost body weight after exercise  In general, drink at least 20 ounces of fluid at all meals  Urinate at least once during the night  Limit caffeine and alcohol intake.

Rebecca LeSaffre is the owner of Lynnfield Boot Camp, and is an ACSM Certified Personal Trainer, a Fitness Nutrition Coach and a Licensed Physical Therapist Assistant. She is qualified to assess what types of exercises will be most beneficial for meeting personal fitness goals, while also helping assure that you use proper form for maximum results and injury prevention. You can contact her via her web site www.lynnfieldbootcamp.com