Day 7 - Calorie Counting

The Problem...

How do excercise apps/machines determine how many calories you have burned?

Why?

• Critical examination of the algorithms behind ICT
• Make mathematical connections between variables
• Experimentation and control variables

I have often wondered about how exercise bikes and running apps are able to calculate the amount of calories burned.  What assumptions do they make to find that number?  This question is an opportunity to combine math and biology (the science often seen as having to do the least with math), as well as tying both into physics.


These are the stats of one of my runs (from last year when I was in way better shape) collected using the free iPhone app RunKeeper.  Apparently, I burned 403 calories. Not too shabby. 

I think an interesting activity would be to try and reverse-engineer where that 403 calories comes from. 

Collect some data...

Students could form groups and collect data on their own devices on a variety of apps and experiment by  playing with different variables (if you look hard enough on the RunKeeper website, there is actually a list of variables used to calculate the calories, but it doesn't tell you how its calculated).  This is a good introduction to control variables.  Students will have to understand they can only change one variable at a time to get useful results.  For example, they may change the weight that is input and see if the calories burned varies linearly with weight.

**If a school has exercise bikes available, they may be a good starting point because there are usually less variables to deal with and the method they use for calculating calories is much simpler (and usually just linear with distance travelled).  What assumptions does the software in these machines make?

Critique and Create...

After coming to some conclusions about how the apps calculate calories, students should critically evaluate the assumptions in the calculation.  I think an interesting way of evaluating this would be for the students to decide what other variables may be important and come up with their own algorithm for calculating calories burned.  They could then submit their recommendations to the app developers.

Curriculum...

This activity encourages the use of control variables and has students creating their own experiments.  They have to think about the mathematical relationships to establish an understanding of the cause and effect of the variables in the app, a critical part of the Scientific Method.

This activity is also a good introduction to metabolism:

• What are calories?
• Why do we use the unit calories instead of joules?
• To give some scale of energy, how many calories does a lightbulb use in an hour?
• How many calories does a litre of gasoline contain?

We can also tie in physics:

• In physics, we say that the total energy in has to equal the total energy out.  Is this true of humans?  
• What other ways do we use energy besides going for a run or bike ride?

21C...

Students participate in Knowledge Construction by performing their own experiments.  They should have the freedom to choose what apps they want to analyse and work in groups to establish the relationships between the variables.  


1. Collaboration: entry - adoption - adaptation - infusion - transformation
2. Knowledge Construction: entry - adoption - adaptation - infusion - transformation
3. Real-World Problem Solving & Innovation: entry - adoption - adaptation - infusion - transformation
6. Use of ICT for Learning: entry - adoption - adaptation - infusion - transformation