Here is Tom Scotto's first post in his official capacity as a Master Instructor here at ICI/PRO –
Indoor cycling instruction keeps progressing and improving and so do the bikes we ride. Today, many of our indoor bikes have more than the ability to add and remove resistance. Bikes are now providing us with cadence, heart rate, power, time and a host of other measurements to guide our rides and training. So I thought it would be good to talk about what these numbers actually mean and get some response from our knowledgeable community about experiences you’ve had or ways you’ve incorporated these tools into your classes and teaching.
OK, they are really not “Killer” calories but that is how is sounds much of the time when I hear people talk about it. We are referring to kcal. This is a scientific abbreviation for kilogram calories or kilocalories. It is generally used to indicate a “small calorie” or gram calorie. When written properly, it is presented with a lowercase “c” as in “cal”. However, like many things we try to understand these days, the inconsistency of how it is display and how it is calculated can create more confusion. So, by its original definition, kcal is 1000 “small” calories or simply a Calorie (note the uppercase “C”).
Without nose-diving into a verbose science lesson (which I’m not qualified to give), kcal or Calories is simply a measurement of energy needed or required. In science terms a kcal represents the approximate “energy” needed to increase the temperature of 1 gram of water by 1 degree Celsius. So on the bike kcal is simply a measurement of how much “energy” we are generating.
So how does the bike know this? Enter the joule.
Since these bikes are also calculating power output (watts – we’ll talk about that in another post), a joule is the measure of energy from the amount of force (mechanical work) required to move an object. Joules can be converted to calories (1 joule equates to 0.2389 calories or 0.0002388459 kilocalorie) – YIKES!!!!! Let’s just say that with my math skills, I’m glad computers can figure this stuff out.
Enough of that Brain Twisting – Is kcal Useful or Accurate?
In a “very” general sense 1 kcal = 1 calorie, but it is better to think of this as the energy that you produced during your ride rather than how many calories your body burned while riding. Here are some factors that affect the true conversion from 1 kcal to 1 Calorie:
(1) Muscle Mass
A person with a higher percentage or body fat will usually burn LESS calories than a person with more muscle mass. Since body fat percentage affects a person’s metabolism, it will affect how much it will cost them (energy) to do a certain amount of work.
(2) Fitness Level
A person who has a greater fitness level will more likely burn LESS calories than someone who is not as fit for the same amount of work or activity. Hence the benefit of training and adaptation.
(3) Body Weight
A person that has more body weight may require LESS energy to push (move) a certain workload (force) than an smaller, lighter person.
(4) Mechanical Efficiency
A rider with good form, posture and technique will fight the mechanics of the bike LESS and may achieve the same output with LESS effort of energy expended.
Because of all the possible variations and factors, it is best to use kcal as a “personal” benchmark. If you generated 500 kcals during a certain ride or training focus, you can try to replicate this on a future ride or try to exceed it. Use it to measure your progress or gauge how hard you may be working during a given class. Just remember, that different pieces of fitness equipment may not calculate kcal the same. This may be due to the mechanics of the equipment (treadmill vs. bike) or because they may include additional measurements (like body weight) into the calculation. Consider each piece of equipment its own animal and use kcal an estimation of how much energy one workout required compared to another.