Calculation of calories burned running
During running, energy expenditure is equal to:
0.85-1.05 kcal/kg of body weight/km
The range is due to the fact that athletes with a “cheaper” athletic technique expend less than those with a less refined technique.
Moreover, we must underline that who have recently started running have expenditures even higher than 1.05 kcal/kg of body weight/km.
How many calories does a 70 kg (154 pound) athlete, with a good technique, expend if he runs for 10, 20, 30 or 40 km?
The expenditure/km is between:
70×0.85=59.5 Kcal and 70×1.05=73.5 Kcal/km.
For increasing mileage, omitting calculations, we obtain:
- 10 km: 595-735 kcal
- 20 km: 1190-1470 kcal
- 30 km: 1785-2205 kcal
- 40 km: 2380-2940 kcal
What does he consume during running?
Carbohydrate consumption during running
- for running higher than anaerobic threshold, therefore the athlete is going very fast, only those are consumed;
- in the pace typical of marathon, they supply 60-70% of the energy;
- for pace lower than that of marathon, they supply less 50% of energy.
Carbohydrate consumption during workout
If we consider a 70 Kg (154 pound) athlete, carbohydrate consumption (in grams) to supply the aforementioned 60% for 10 km (energy expenditure between 595 and 735 kcal) is equal to:
(0.6×595)/4=about 90 g and (0.6×735)/4=about 110 g
- 20 km: 180-220 g
- 30 km: 270-330 g
- 40 km: 360-440 g
Lipid consumption during workout
- 10 km: 26-32 g
- 20 km: 53-65 g
- 30 km: 80-100 g
- 40 km: 105-130 g
A formula, called “Arcelli’s formula”, exists by which we can estimate the grams of lipids consumed during running/walking:
grams of consumed lipids=(km x kg of body weight)/20 (30 if we walks).
Daily protein requirements and running
Protein requirements of a sedentary man (adult) are equal to 0.8 g/kg of body weight/day (OMS source).
So, the basal requirements of the 70 kg (154 pound) athlete are :
About 3-5% of the energy expended to sustain muscular work comes from amino acids (coming from proteins) oxidation.
With calculations as those made for carbohydrates and lipids, for the just seen distances, we obtain:
- 10 km: 61-64 g (0.87-0.92 g/kg of body weight/day)
- 20 km: 66-73 g (0.94-1.04 g/ kg of body weight/day)
- 30 km: 71-81 g (1.01-1.16 g/ kg of body weight/day)
- 40 km: 76-89 g (1.09-1.28 g/ kg of body weight/day)
Leaving out athletes who train daily for 30 km or more, we obtain values slightly higher than 0.8/kg of body weight/day of the general sedentary population.
Actually, the amount is a bit to increase because some nitrogen (proteins) is lost with sweating as well as urine.
Howeve, we are always at lower values than 1.5 g/kg of body weight/day.
Fluid and mineral loss during running
Water losses depend on the amount of sweat that athlete produces that in turn depend on:
- air temperature and humidity;
- solar radiation.
The loss will be greater the higher these values are.
Finally, sweat is produced in different amount in any person.
By sweat, mineral lost are mostly:
- sodium (Na+) and chlorine (Cl–), about 1 g/L of sweat in athlete accustomed to train in environmental conditions that cause a great sweating;
- potassium (K+) about 15% of sodium;
- magnesium (Mg2+) still less, about 1% of sodium.
The amount of mineral salt lost depends on how much sweat we produce, and it increases if we consider not accustomed athletes.
Physical activity and sodium
During physical activity, the mineral we need most of all is sodium.
After physical activity, runner or who sweats very much (studies conducted initially on foundry workers) tends to eat saltier, both as food and as salt on food. We talk of “selective hunger”.
Probably, the “selective hunger” doesn’t not exist for potassium and magnesium (it seems that is not true for all subjects, usually 2 of 3).
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;39:377-390 [PDF]
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 [Abstract]
Wolinsky I., Driskell J.A. Sport nutrition: energy metabolism and exercise. CRC Press; Taylor & Francis Group, 2008