Ma Be in USMA 18535 wrote: > I'd like someone here to help me understand the relationship between the >figure that treadmills/bicycle exercising machines give us in W with >energy we used (which, unfortunately, is invariably reported in calories). > >Something simply is not making any sense to me. Yesterday I was >monitoring how my wife was doing in the bike machine and I'd say she was >spending an average of 120 W+ in her exercise routine. Upon checking the >calorie reading it was stating that she spent about 260 calories during >her 30-min session! Am I missing something here?... > >Note: Doing the calcs would give us the following: >120 W x 30 min x 60 s = 216 kJ =~ 52 Cal >This is intriguing because I know I usually spend about 2 MJ of energy per >half-hour of running I do on my treadmill at ~12.5 km/h speed.
The following item in this morning's Gloobe and Mail may explain the mystery. It says: "A worker doing hard physical labour all day--or a felon turning a treadmill--can put out about 100 watts of power. That's the output, in the form of a little light and a lot of heat, of the familiar light bulb," writes Steven Vogel in Natural History magazine. "What about the fuel? We are at best only about 25 per cent efficient, so an output of 100 watts requires a minimum input of 400 watts, which translates (when we multiply it by 0.86) into about 350 Calories per hour. Burning a tenth of a pound of good fuel--fat--yields about 350 Calories, so working at 100 watts for eight hours costs less than a pound of body fat--still nearly double a human male's normal energy use." Does that explain the reading of your wife's bike machine? Was the maker of the machine trying to show the body thinning power of the machine in terms of the food input required to support the energy needed in pedaling? Joseph B.Reid 17 Glebe Road West Toronto M5P 1C8 TEL. 416-486-6071
