For every physical activity, the body requires energy and the amount depends on the duration and type of activity. Energy is measured in calories and is obtained from the body stores or the food we eat. This article looks at the energy expenditure for walking and running.
A linear relationship exists at walking speeds of 3 to 5 km/hr of oxygen consumption but at faster speeds, oxygen consumption rises making walking less economical.
Body mass can be used to predict energy expenditure with reasonable accuracy at walking speeds of 2 to 4 mph (3.2 to 6.4 km/hr). McArdle (2000) details the number of calories you will burn per minute for ranges of body mass (weight) and speed when you walk on a firm level surface.
If your body mass is 64 kg and you walk at a speed of 5.63 km/hr then you will burn approximately 4.6 Calories/minute - if you walk for one hour you will burn 60 × 4.6 = 276 Calories
When running at identical speeds, a trained distance runner runs at a lower percentage of their aerobic capacity than an untrained athlete does, even though the oxygen uptake during the run will be similar for both athletes. The demarcation between running and jogging depends on the individual's level of fitness. Independent of fitness it becomes far more economical from an energy viewpoint to change from walking to running when your speed exceeds 8km/hr (5mph). Above 8km/hr the oxygen intake for a walker exceeds the oxygen intake of a runner. At 10km/hr the walker's oxygen (O2) uptake is 40 ml/kg/min compared to 35 ml/kg/min for the runner. See McArdle (2000)  .
Body mass can be used to predict energy expenditure with reasonable accuracy when running on a firm level surface (road, track or grass). The number of calories required to run 1 km equals your weight in kg (a runner of 78 kg will burn 78 Calories/km).
One litre of oxygen equals five calories so our 78kg runner utilises 15.6 litres of oxygen per kilometre.
McArdle (2000) details the number of calories you will burn per minute for ranges of body mass (weight) and speed when you run on a firm level surface
How Exercises Compare
The following table, adapted from McArdle (2000), contains the approximate caloric expenditure in a 30 minute period of exercise for a person weighing 68kg for various exercises and intensity of work. Add 10% for every 7kg over 68kg and deduct 10% for every 7kg under 68kg
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