Health Data Dump, 2021

By | January 10, 2022

I have an Apple Watch that collects a lot of my personal health data. But… it doesn’t use make very good use of it and doesn’t let me export it outside of the Apple universe for my own analysis. So, this post will be the start of a yearly series that collates and analysis said data.

Data Dictionary

The data series I collate and analyze are shown below. Inclusion criteria is based on whether I deem it useful and am able to accurately record it. I will collate monthly averages of daily data. Details below include the data series: Name, Definition, Source and Notes.

Active Energy

  • Definition: Estimate of energy burnt over and above your resting energy use, Active energy use includes activities such as walking slowly, pushing your wheelchair and household chores, as well as exercise such as biking and dancing.
  • Source: Apple watch
  • Notes: I take my apple watch off when I enter the water (surfing/swimming) so it will under report activity.

Resting Energy

  • Definition: Estimate of the energy your body uses each day while minimally active. Additional physical activity requires more energy over and above resting energy
  • Source: Apple watch
  • Notes:

Total Energy

  • Definition: Your total energy use is the sum of your resting energy and active energy.
  • Source: Apple watch
  • Notes:

Walking + Running Distance

  • Definition: Sum of walking and running distance.
  • Source: Apple watch
  • Notes:

Workout Time

  • Definition: Total minutes spent working out.
  • Source: Apple watch
  • Notes: I take my apple watch off when I enter the water (surfing/swimming) so it will under report activity.

VO2 Max

  • Definition: Maximum amount of oxygen your body can consume during exercise.
  • Source: Apple watch
  • Notes:

Resting Heart Rate

  • Definition: Average beats per minute measured when you have been inactive or relaxed for several minutes (excluding sleep).
  • Source: Apple watch
  • Notes:


  • Definition: Body weight.
  • Source: Apple watch
  • Notes:

Time Asleep

  • Definition: Time spent asleep (distinct from time in bed).
  • Source: Apple watch
  • Notes:

Stand Minutes

  • Definition: Stand Minutes are the minutes in each day that you are standing and moving.
  • Source: Apple watch
  • Notes: I think its just total minutes in a day that you are standing.

Raw Data, Monthly Averages, 2021

MeasureJan FebMarAprMayJunJulAugSepOctNov Dec
Active Energy (KJ)202921932327205011411374163530163322271420891242
Resting Energy  (KJ) 774076717848773676857326749376007773782577727311
Total Energy (KJ) 9769986410175978688268700912810616110951053998618553
Walking + Running Distance (Km)
Workout Time (Mins)6618123871516235887675726
VO2 max 5048.947.148.548.247.949.55050.751.750.450
Resting Heart Rate (Bpm)646664636357585752525557
Weight (Kg)73.575.177.179.1582797878.0276.9774.474.573.5
Time Asleep (Hrs)
Stand Time (Mins)108114104854040479194766964

Descriptive Statistics

  Active Energy  Resting Energy  Total Energy Walking + Running Distance Workout Time (Mins) VO2 max Resting Heart Rate Weight   Time Asleep    Stand Minutes
Standard Error198.019352.51383232.9720.72271910.03060.3804821.3980510.759580.3467317.525042
Standard Deviation685.959181.9132807.03862.50357334.747031.3180284.8429892.6312631.20111126.06751
Sample Variance470539.733092.42651311.36.2678791207.3561.73719723.454556.9235451.442668679.5152


 Active Energy Resting Energy Total EnergyWalking + Running DistanceWorkout Time (Mins)VO2 max Resting Heart RateWeightTime Asleep Stand Minutes
Active Energy 1
Resting Energy 0.591
Total Energy0.980.731
Walking + Running Distance0.950.450.911
Workout Time (Mins)0.630.700.690.441
VO2 max 0.470.150.430.640.001
Resting Heart Rate-0.370.11-0.29-0.47-0.03-0.701
Time Asleep -0.02-0.17-0.05-
Stand Minutes0.650.570.680.600.590.110.33-0.48-0.571



Basically, I perform 3 different types of physical exercise: running/walking, stationary exercise (e.g. gym), and water based exercise (e.g. surfing). When I wear my Apple watch, it measures my overall activity level, my total distance traversed, and my time spent working out. So, at first glance, you would think that it paints a pretty good picture of my overall activity, but, practically speaking, none of the metrics are a perfect measure.; all the activity metrics will under-record water based exercise as I don’t take my Apple Watch into the water, workout time is biased downwards as I often forget or simply don’t record workouts, and Walking + Running Distance doesn’t record stationary exercise, such as gym exercises. So, in light of these flaws, which metric should I use? Examining correlations, Active Energy captures a lot of the variation in Walking + Running Distance (0.95), and a decent amount of Workout Time (0.65) (lower correlation of workout time can be explained by me not recording all workouts). Suggesting that it is perhaps the best measure to use.

Active Energy looks like a camel with two humps; the first hump representing my weightlifting at the beginning of the year and the second hump my marathon training. Given these are somewhat casual shocks to my health, they provide a good opportunity to assess how my other health metrics respond to these different activities.

This is hardly a robust casual analysis, but visual inspection reveals several important things: (a) my weightlifting period was substantially positively associated with my weight gain, but weakly related to sleep (positive) and resting heart rate (negative), and (b) my marathon training period was substantially negatively related to my weight, but moderately related to sleep (positive), and resting heart rate (negative).


Wow… what a ride! Up 9kg during the first half of the year and then back down 9kg during the second half. What the hell happened? First, over March and April I joined an Olympic weightlifting club and my workout time skyrocketed (over 120mins/day in march), and so did my appetite, resulting in most of my weight gain. Second, over the middle part of the year (Apr-Jul), I stopped weightlifting, ate moderately, and started surfing as the winter swell arrived, resulting in 2-3kg of total weight loss. Third, from Aug until the end of the year, I started running (over 10kms/day in Sep), kept surfing, and kept eating – albeit healthier – resulting in a steady weight decrease.

Also, rather than just recording weight, I should start recording food quantity as well as quality; add a little more color to the picture. I don’t want to put too much effort into this – like calorie counting – but I should be happy to give myself a daily score out of 10 for food quality and quantity.


Lol… I only slept for an average of 4-6 hours over Jan and Feb. Basically, I was stressed out and working my ass off at a private equity internship. Otherwise, my sleep time has slightly increased over the course of the year, peaking during August when my marathon training entered full swing. I hope this sleep trend continues and I crack the 8 hour average next year. I love sleep!

Also, while hours slept is a nice metric, there is more to be measured! For example, sleep quality and variability. I’ll start looking for ways to start recording these so I can bring a bit more color to next years picture.

Other things to track

To add additional pixels to my health portrait, I am also going to start daily tracking of some more qualitative/subjective health metrics. To measure them, I plan to simply give each of these metric a score out of 10 at the end of each day. These metrics are (a) how happy I felt, (b) how energetic I felt, and (c) how productive I felt.