Expert: Ken Alan - 3/9/2009

Question
QUESTION: Hello Ken,
Not sure you can answer this, but thought I'd try.
I use a treadmill for exercise, and hopefully to burn calories.  I would like to know why there are some differences with calories burned..
I enter the same speed, incline time etc.  I exercise with someone else. she doesn't always use the incline.  sometimes a slower speed.  Yet she always burns more calories than I do.  Sometimes I'll burn 170 sometimes less..she always will burn 180 190 200 etc. Why is this?
Thank you


ANSWER: There is some small, different element about your workouts, that you're not noticing.  Or your friend is entering different data than you.  Is it her weight/age?  If you're using the same machine, is the speed and time exactly the same as what you're doing? Are you using the same treadmill?  If you're using different makes/models, small differences are common.  Is she doing a cool-down on the treadmill that is adding the few extra calories? The machine, if you're using the same make/model, wouldn't abitrarily give different calorie burn totals for you and friend if everything you enter is identical and your speed/time are exactly the same.  There is some factor that is giving her a higher total. Even two minutes longer can equate to 10 calories or more difference, and it's easy to miscaculate your time by two minutes (example, when the timer hits "30 minutes", she may stay on it another 55 seconds and it would still say "30 minutes".)
Hope this helps.

---------- FOLLOW-UP ----------

QUESTION: thanks Ken for your response, but wanted to answer some of your questions.  I'm the one that will do a cool down she doesn't always care to.  WE go to a gym so we don't always use the same treadmills, and they are all the same make.
She is older, and is a different weight (heavier than I am).  I use the incline she doesn't always.  I use a faster speed sometimes she uses the same. As i said I 'm the one who stays on longer, because i do a cool down.  Someone did mention that because our weights are different it could be the reason.  But I walk fast on the treadmill  they tell me this could be a problem if I overdo.
thanks

Answer
There are a lot of variables from what you have described.  The primary culprit is probably the weight difference between the two of you.  A 125 pound person going at a speed of 5 mph on a treadmill may burn around 9 calories per minute.  A 160 pound person going at the same speed may burn around 11 calories per minute.  Heavier people burn more calories exercising at the same speed, time, and relative intensity as a ligher weight individual.  Caloric burn is also affected by fitness level, hormonal status, environment (hot/cold), stress, age, medications, and diet.

"Overdoing it" is not the reason you seem to be burning "less calories" than your friend.  Is the machine punishing you by saying you have burned less calories than your friend because it believes you are overdoing it?  I don't think so.  Equipment isn't that smart...yet!  It has no way of knowing if you are overdoing it or underdoing it.  It just knows you're doing it. It's not judgemental!   Don't be concerned about the difference in total caloric burn.  It's not a significant difference anyway. We'd have to get the two of you on the exact same machine, time you meticulosly, and make sure there are no other variables that change to compare the "caloric burn" readout the machine gives you.  I bet when this is done, a primary reason in two different outcomes is attributed to body weight differences.

Hope this helps.