The available energy contents of various kinds of food are often listed in 'Calories' charts. One of these food 'Calories' is actually 1000 calories of the type defined in this experiment, i.e. 1 food Calorie = 1 kcal or kilocalorie. Assuming the human body is 50% efficient in the conversion of food Calories into mechanical work, how many turns of the crank would have been necessary to work off an average breakfast of about 600 food Calories? An efficiency of 50% means that only 50% of the food energy intake can be used for mechanical work. The other 50% is wasted in the form of heat (sweating).