The Great Stationary Cycling Experiment
Saturday, September 22, 2012
In yet another experiment borne of message board discussions, the question arose as to whether your body weight actually does make much difference in stationary cycling. One poster said that it does, because Spark gives significantly different burn rates for heavier people for the same workout. Others said that the resistance is entirely magnetic and your individual body weight is irrelevant.
So the experiment...
Using myself as an estimation, therefore pretty identical actual HRs during the two bouts, so the only variable is the weight plugged into the device...
10 mins stationary cycling at 18mph, with the weights of 250lbs and 120lbs plugged into the Bike and the HRM.
Spark Stationary = stationary cycling,vigorous, greater-than 15mph
Calories burned at 250lbs:
Spark Stationary: 219
Calories burned at 120lbs
Spark Stationary: 83
The bike and the HRM reported similar but only slightly lower burn rates for the lighter person, given the same HR recorded over the durations. Spark, which doesn't ask for HR, indicated an incredibly significantly higher burn for the heavier person, and a burn more matching the other devices for the lighter person.
Notice that Spark's figure of 219 for 10 minutes of exercise for the obese person is 22 cals per minute - which is pretty much physically impossible. Exercise almost never gets above 14 cpm, and most exercise is 6-12cpm depending on intensity and your weight. Given cycling is a very low intensity lower-body-only activity, it's incredibly unlikely that it would realistically be anywhere near 22 cpm even for the most grossly overweight of individuals.
Spark erroneously takes your weight into consideration when calculating burn on a magnetic resistance device. Neither the device, nor my HRM, report that the burn would be significantly different for a heavier person, but Spark reports a phenominal difference - more than 2.5 times the burn.
Therefore I would STRONGLY caution AGAINST using Spark's estimates for any magnetic resistance workout, and instead use an HRM, or the machine reported figure, or seek an average from other online sources.