Calories burned, and water and minerals lost during running

Calorie, carbohydrate, fat, and protein expenditure, and water and mineral losses during runningDuring running, athletes burn calorie, and lose water and salts in amounts depending on various factors such as the technique, training level, environmental conditions, and physiological characteristics of each runner. The knowledge of these factors allows to plan an adequate diet both during workout  and recovery, with the aim of optimizing performance.
Below we will analyze the energy expenditure of runners engaged in workouts on various distances, the amounts of carbohydrates, lipids, and proteins oxidized to meet the energy requirements, and which minerals are lost in sweat.

CONTENTS

Energy expenditure during running

During running energy expenditure is equal to 0.85-1.05 kcal per kilogram per kilometer.
This range is due to the fact that athletes with a good technique spend less than those with a poor technique.
A 70 kilogram (154 pound) athlete has an energy expenditure per kilometer between:

70 x 0.85 x 1 = 59.5 kcal
and
70 x 1.05 x 1 = 73.5 kcal

The table shows the calculations to determine the energy expenditure of the athlete to run 10, 20, 30, and 40 kilometers.

Distance

Energy expenditure

10 km 0.85 x 70 x 10 = 595 kcal
1.05 x 70 x 10 = 735 kcal
20 km 0.85 x 70 x 20 = 1190 kcal
1.05 x 70 x 20 = 1470 kcal
30 km 0.85 x 70 x 30 = 1785 kcal
1.05 x 70 x 30 = 2205 kcal
40 km 0.85 x 70 x 40 = 2380 kcal
1.05 x 70 x 40 = 2940 kcal

Note: who has started running for a short time ago has an energy expenditure even higher than 1.05 kcal per kilogram per kilometer.

During running, the energy for muscle work derives from the oxidation of carbohydrates, lipids, and proteins. Carbohydrates and lipids are the main energy source, and their oxidation rate depends on the intensity of exercise: as it increases, the percentage of lipid oxidation decreases whereas that of carbohydrates increases, as summarized below.

Intensity Fuel
30% VO2max Mainly fats
40-60% VO2max Equally fats and carbohydrates
75% VO2max Mainly carbohydrates
80% VO2max Almost only carbohydrates

Note: The failure to use the suitable fuel can promote fatigue and lead to overtraining.

Then, when running above the anaerobic threshold, the oxidation of carbohydrates can provide the entire energy requirement. At marathon pace, carbohydrates provide 60-70% of the energy requirement, whereas at lower pace they provide less than 50% of energy requirement.
Below, the amounts of carbohydrates, lipids, and proteins oxidized during workout are analyzed. During workout ,the energy expenditure is covered for about 60% by carbohydrates, for about 40% by lipids, whereas the residual percentage, between 3 and 5%, by proteins.

Carbohydrate oxidation during workout

For a 70 kilogram runner the amount of carbohydrates oxidized per kilometer is between:

(0.6 x 59.5) /4 = 8.9 g/km
and
(0.6 x 73.5) /4 = 11 g/km

Note: carbohydrates provide, on average, 4 kcal per gram.
The table shows the calculations to determine the amount of carbohydrates oxidized when the athlete runs 10, 20, 30, and 40 kilometers.

Distance Carbohydrate expenditure

10 km

[(0.85 x 70 x 10) x 0.6 ] / 4 = 89 g
[(1.05 x 70 x 10) x 0.6 ] / 4 = 110 g

20 km

[(0.85 x 70 x 20) x 0.6] / 4 = 179 g
[(1.05 x 70 x 20) x 0.6] / 4 = 221 g

30 km

[(0.85 x 70 x 30) x 0.6] / 4 = 268 g
[(1.05 x 70 x 30) x 0.6] / 4 = 331 g

40 km

[(0.85 x 70 x 40) x 0.6] / 4 = 357 g
[(1.05 x 70 x 40) x 0.6] / 4 = 441 g

Lipid oxidation during workout

By calculations similar to those for carbohydrates, we determine the amount of lipids oxidized per kilometer, which is between:

(0.4 x 59.5) / 9 = 2.6 g/km
and
(0.4 x 73.5) / 9 = 3.3 g/km

Note: lipids provide, on average, 9 kcal per gram.
The table shows the calculations to determine the amount of lipids oxidized when the athlete runs 10, 20, 30, and 40 kilometers.

Distance

Lipid expenditure

10 km [(0.85 x 70 x 10) x 0.4] / 9 = 26 g
[(1.05 x 70 x 10) x 0.4] / 9 = 33 g
20 km [(0.85 x 70 x 20) x 0.4] / 9 = 53 g
[(1.05 x 70 x 20) x 0.4] / 9 = 65 g
30 km [(0.85 x 70 x 30) x 0.4] / 9 = 79 g
((1.05 x 70 x 30) x 0.4] / 9 = 98 g
40 km [(0.85 x 70 x 40) x 0.4] / 9 = 106 g
[(1.05 x 70 x 40) x 0.4] / 9 = 131 g

Protein oxidation during workout

Protein requirements of adults are equal to 0.9 grams per kilogram of body weight, and, for a 70 kilogram athlete is:

70 x 0.9 = 63 g

During workout  the energy expenditure is covered for about 3-5% by protein oxidation.

The table shows the calculations to determine the amount of proteins oxidized when the athlete runs 10, 20, 30, and 40 kilometers, and proteins provide 3% of the energy requirement.

Distance

Protein expenditure (3%)

10 km [(0.85 x 70 x 10) x 0.03)] / 4 = 4.5 g
[(1.05 x 70 x 10) x 0.03)] / 4 = 5.5 g
20 km [(0.85 x 70 x 20) x 0.03)] / 4 = 8.9 g
[(1.05 x 70 x 20) x 0.03)] / 4 = 11 g
30 km [(0.85 x 70 x 30) x 0.03)] / 4 = 13.4 g
[(1.05 x 70 x 30) x 0.03)] / 4 = 16.5 g
40 km [(0.85 x 70 x 40) x 0.03)] /4 = 17.9 g
[(1.05 x 70 x 40) x 0.03)] /4 = 22.1 g

Note: proteins provide, on average, 4 kcal per gram.

For energy expenditure of 0.85 and 1.05 kcal per kilogram per kilometer, the average additional protein oxidation per kilogram to run 10, 20, 30, and 40 kilometers, rounded to the second decimal place, is:

  • 10 km: [(4.5 + 5.5) / 2] / 70 = 0.07 g
  • 20 km: [(4.5 + 5.5) / 2] / 70 = 0.14 g
  • 30 km: [(4.5 + 5.5) / 2] / 70 = 0.21 g
  • 40 km: [(4.5 + 5.5) / 2] / 70 = 0.29 g

Finally, adding the daily protein requirement of adults, the total protein requirement of a 70 kilogram runner, for the four distances, is:

  • 10 km: 0.07 + 0.9 = 0.97 g
  • 20 km: 0.14 + 0.9 = 1.04 g
  • 30 km: 0.21 + 0.9 = 1.11 g
  • 40 km: 0.29 + 0.9 = 1.19 g

By calculations similar to the previous ones, we determine the overall protein requirement when proteins provide 5% of the energy requirement.

  • 10 km: 0.12 + 0.9 = 1.02 g
  • 20 km: 0.24 + 0.9 = 1.14 g
  • 30 km: 0.36 + 0.9 = 1.26 g
  • 40 km: 0.48 + 0.9 = 1.38 g

Excluding athletes who run 30 kilometers or more every day, the values are slightly higher than 0.9 grams per kilogram of body weight.
In reality, the daily protein requirement is just slightly higher because a certain amount of nitrogen, hence proteins, is lost, as well as in the urine, also through sweating.

Water and minerals loss during running

Water losses depend on the amount of sweat produced, that depends on:

  • air temperature and humidity;
  • solar radiation.

The loss will be greater the higher these values are.
Finally, the amount of sweat produced is different from person to person.

Minerals lost in sweat are mostly:

  • sodium (Na+) and chlorine (Cl), about 1 gram per liter of sweat in heat acclimatized athletes;
  • potassium (K+), in an amount equal to about 15% of the sodium lost;
  • magnesium (Mg2+), in an amount equal to about 1% of the sodium lost.

The amount of minerals lost depends on how much sweat is produced, and it increases in non-heat acclimatized athletes.

The table shows the values, in grams per liter, of the minerals lost in sweat for non-heat and heat-acclimated athletes.

  Non-heat acclimated athletes

heat acclimated athetes

Sodium

1.38

0.92

Chlorine

1.5

1.00

Potassium

0.20

0.15

Magnesium

0.01

0.01

Total

3.09

2.08

Therefore, during physical activity, sodium is the mineral we need most of all.
After physical activity, runner, or who sweats heavily, tends to eat saltier food. This effect, known as selective hunger, was discovered, for sodium, in studies conducted on foundry workers. Probably, the selective hunger doesn’t not exist for potassium and magnesium.

References

Mahan L.K., Escott-Stump S.: “Krause’s foods, nutrition, and diet therapy” 10th ed. 2000

Sawka M.N., Burke L.M., Eichner E.R., Maughan, R.J., Montain S.J., Stachenfeld N.S. American College of Sports Medicine position stand: exercise and fluid replacement. Med Sci Sport Exercise 2007;39(2):377-390 doi:10.1249/mss.0b013e31802ca597

Shils M.E., Olson J.A., Shike M., Ross A.C.: “Modern nutrition in health and disease” 9th ed. 1999

Shirreffs S., Sawka M.N. Fluid and electrolyte needs for training, competition and recovery. J Sport Sci 2011;29:sup1, S39-S46 doi:10.1080/02640414.2011.614269