The need for water far surpasses the need for any other nutrient. The body relies on watery fluids as the medium for all of its life-supporting activities, and if it loses too much water, its well-being becomes compromised.

Obviously water is lost thru sweat but water is also exhaled thru the lungs as water vapor. During physical activity, water losses from both routes are significant, and dehydration becomes a threat. Dehydration’s first symptom is fatigue: a water loss of even 1-2% of body weight can reduce a person’s capacity to do muscular work. With water losses of about 7%, a person is likely to collapse.

FLUID LOSSES VIA SWEAT

Working muscles produce heat as a by-product of energy metabolism. During intense activity, muscle heat production can be 15-20 times greater than at rest. The body cools itself by sweating. Each liter of sweat dissipates almost 600 kcal of heat (kcal is a unit of measurement – you’re not burning 600 cal by sweating out a liter of water), which prevents a rise in body temperature of almost 18 degrees F. The body routes its blood supply through the capillaries just under the skin, and the skin secretes sweat to evaporate and cool the skin and the underlying blood. The blood then flows back to cool the deeper tissues and chambers of the body.

HYPERTHERMIA

In hot, humid weather, sweat doesn’t evaporate well because the surrounding air is already laden with water vapor. In hyperthermia, body heat builds up and triggers maximum sweating, but without sweat evaporation, little cooling takes place. In these conditions, active people must take precautions to prevent heat stroke. To reduce the risk of heat stroke, drink enough fluid before and during the activity, rest in the shade if applicable, and wear light weight clothing that allows sweat to evaporate. If you ever experience any of the symptoms of heat stroke listed below, stop the activity, sip some fluids, seek shade or cool area, and ask for help. Heat stroke – although will most like not apply to the body building community – can be fatal, young people often die from it, and these symptoms demand attention.

• Headache
• Nausea
• Dizziness
• Clumsiness
• Stumbling
• Sudden cessation of sweating (hot dry skin)
• Confusion or mental changes

FLUID REPLACEMENT via HYDRATION

Endurance athletes can easily lose 1.5 liters or more of fluids each hour of activity. To prepare for fluid losses, a person should hydrate before activity. It is recommended to ingest approx. 2-3 cup 2 hr prior to activity and then 1-2 cup 15 min prior. To replace fluid losses, the person should rehydrate during and after activity. It is recommended to weigh yourself prior to and after activity. During activity, you should ingest approx. 8-10 fluid oz (1-1 ½ cup) every 15-20 minutes. Depending on the change in total body weight post activity, 16 oz of fluids (2 cup) should be ingested per pound of weight lost at a rate of 8-10 oz every 15-20 minutes. Even still, in hot weather, the GI tract may not be able to absorb enough water fast enough to keep up with sweat losses, and some degree of dehydration may be inevitable.

ELECTROLYTE LOSSES & REPLACEMENT

When a person sweats, small amounts of electrolyte – the electrically charged minerals sodium, potassium, chloride, and magnesium – are lost from the body along with water. Losses are greatest in beginners; training improves electrolyte retention. These electrolytes are essential to muscular contractions and without them they simply will not function.

To replenish lost electrolytes, a person ordinarily needs only to eat a regular diet that meets energy and nutrient needs. In events lasting more than one hour, sports drinks may be needed to replace fluids and electrolytes. Due to the antagonistic relationship between potassium and sodium, salt tablets can worsen dehydration and impair performance by increasing potassium losses, irate the stomach, and cause nausea or vomiting.

In summary: Active people need to drink plenty of water; endurance athletes need to drink both water and carbohydrate-containing beverages, especially during activity. During events lasting longer than 3 hrs, athletes need to pay special attention to replacing sodium losses to prevent hyponatremia – a decrease in the concentration of sodium in the blood. Symptoms of hyponatremia include headaches, vomiting, bloating or water retention, confusion seizure.

I realize that the risk of dehydration is mostly a moot point for body builders. I, personally, am not a body builder by any stretch of the imagination. I enjoy employing various cross-training techniques in terms of improving functional fitness. I enjoy playing beach volleyball at a completive level, and where I am the environment is hot and humid most year round. My approach to fitness, if you haven’t noticed already, is a holistic approach. I like to provide balance and understanding in all aspects, so I hope some of you find this interesting and useful.