The following charts and narrative are excerpted with permission from the book, The Peformance Zone: Your Nutrition Action Plan for Greater Endurance & Sports Performance by Dr. John Ivy, Ph. D, and Dr. Robert Portman, Ph D. Basic Health Publications, Inc. 2004

Effects of Increasing Dehydration on Physical Performance

Body Water Loss Effects
0.5% Increased strain on the heart
1% Reduced aerobic endurance
3% Reduced muscular endurance
4% Reduced muscle strength; reduced fine motor skills; heat cramps
5% Heat exhaustion; cramping; fatigue; reduced mental capacity
6% Physical exhaustion; heatstroke


Dave Scott comments:  A 2% water loss is the maximum amount of water loss before more serious effects.  Most people experience greater cardiac stress at 2% and higher.

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Average Sweat Rate at Moderate Exercise Intensity
For Different Temperatures

 
Sweat Rate (ounces per hour)
Temperature Low Moderate High
40°F 12 17 35
55°F 15 22 31
70°F 22 27 47
90°F 31 37 75

Dave Scott’s comments: Humidity, body weight, fitness level and genetics will affect your sweat rate.

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Ideal Nutrient Composition for a Sports Drink During Exercise

Nutrient Objectives Ideal Composition (per 12 oz water)
  • Replace fluids and electrolytes
  • Preserve muscle glycogen
  • Maintain blood glucose levels
  • Minimize cortisol increases
  • Set the stage for a faster recovery
  • High-glycemic carbohydrates, such as glucose, sucrose, and maltodextrin:
    20-30 g
  • Whey protein: 5-6 g
  • Vitamin C: 30-120 mg
  • Sodium: 100-250 mg
  • Potassium: 60-120 mg
  • Magnesium: 60-120 mg

Dave Scott’s comments: 4 calories = 1 gram.  Concentration in calories is 80-120 calories. 

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Creating your nutrition action plan

Every athlete is different, and therefore each has his or her own unique nutritional requirements. In this section, we describe how you can tailor these general recommendations into your own nutrition action plan. It involves a few simple calculations based on your weight and your activity level. If you participate in more than one sports activity, create a separate nutrition action plan for each.

Compute your total caloric expenditure

Figuring out your total caloric expenditure is the most important calculation you'll make. From this figure, you can determine your fluid and carbohydrates needs. Total caloric expenditure is a function of your exercise activity, the intensity and duration of your exercise activity, the intensity and duration of your exercise, and your weight in pounds. The table below lists the energy expenditure values for a wide range of exercise activities. To determine your total caloric expenditure, select the energy expenditure value from the table below based on your activity and intensity. This number is multiplied by your weight in pounds and your workout duration.

For example, if you train by running at an eight-minute per mile pace, weight 150 pounds, and exercise for forty-five minutes, your calculated caloric expenditure would be:

Total Caloric Expenditure = .09 (cal/min/lb) x 150 lb x 45 min = 607 calories

Dave Scott's Comments: After you've computed the total number of calories that you've expended, you now need to determine how many calories you need to replace. The last chart below, entitled "Determining Fluid and Nutrient Needs During Exercise," will help you determine that number. You need to replace 25-30% of total calories burned during your training session. In the example above, 607 calories were burned. 25-30% of 607 calories equals roughly 150-200 calories to replace for this 45 minute session.  

 

Energy Expenditure Values For Different Exercise Activities

Activity Energy Expenditure Value (cal/min/lb) Activity Energy Expenditure Value (cal/min/lb)
Aerobic high impact 0.07 Running: 7 min/mile 0.10
Aerobic: low impact 0.04 Running: 8 min/mile 0.09
Basketball 0.06 Running: 9 min/mile 0.09
Cycling 10 mph 0.06 Running: 11.5 min/mile 0.06
Cycling 15 mph

0.08

Skiing vigorous/racing 0.06
Cycling 17.5 mph 0.09 Soccer Competitive 0.08
Cycling > 20 mph 0.12 Strength Training: Circuit 0.06
Football 0.07 Strength Training: Vigorous 0.05
Golf (carrying clubs) 0.04 Swimming back stroke 0.08
Gymnastics 0.03 Swimming breast stroke 0.07
Mountain bike 0.06 Swimming freestyle 50 yards/min 0.06
Running, cross-country 0.07 Swimming freestyle 75 yards/min 0.08
Running: 5.5 min/mile 0.13 Tennis Match 0.08
Running: 6 min/mile 0.11 Volleyball 0.02

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Determining Fluid and Nutrient Needs During Exercise

Total Caloric Expenditure (cal) Total Fluid Loss Thru Sweating (oz) Target Carb Caloric Intake* (cal) Carb (g) Protein (g) Sports Drink** (oz) Water (oz) Total Target Fluid Intake (oz)
200 9 50 12.5 3.1 7 1.9 8.9
250 11 63 15.3 3.9 9 2.4 11.4
300 14 75 18.8 4.7 11 2.9 13.9
350 16 88 21.9 5.5 12 3.4 15.4
450 20 113 28.1 7.0 16 4.4 20.4
500 23 125 31.3 7.8 18 4.8 22.8
550 25 138 34.4 8.6 19 5.3 24.3
600 27 150 37.5 9.4 21 5.8 26.8
650 29 163 40.6 10.2 23 6.3 29.3
700 32 175 43.8 10.9 25 6.8 31.8
750 34 188 46.9 11.7 26 7.3 33.3
800 36 200 50.0 12.5 28 7.8 35.8
850 38 213 53.1 13.3 30 8.2 38.2
900 41 225 56.3 14.1 32 8.7 40.7
1000 45 250 62.5 15.6 35 9.7 44.7
1200 54 300 75.0 18.8 42 11.6 53.6

* 25% of Caloric Expenditure, ** (6% carb/1.5% protein)

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