Data Fit - Heart Rate Analysis of Crossfit

Data Fit

One of my workout friends at the gym recently bought a Polar h7 chest strap heart rate monitor. We did a workout while he collected data about how his heart was working and we geeked out about it for quite a while afterwards. While we were wondering what statistics we could calculate, or how we could generate a linear regression from the data, I had the thought that I could make some really interesting data visualizations out of this. So I bought a heart rate monitor for myself, started monitoring my workouts and low and behold, I got some very cool data. Then I took this data and tried to draw some conclusions about what how I have been performing, and about Crossfit classes as a whole. I will only analyze one class here, but there is so much more analysis that could be done.

Crossfit Classes

Heart Rate vs. Time During Crossfit Class

Heart Rate vs. Time During Crossfit Class

The workout was as follows

Warm Up:

2 Rounds
24 Plank Knee to Elbows
12 Pike Feet Walkout
12 Bar Hollow Hold
12 Hand Walkouts
Rest 30 seconds between movements

Technique / Speed: EMOM 8 minutes

5 Reps Hang Full Clean @95 / 65lbs

Metcon: 2 Parts

AMRAP 5 min
5 Power Cleans @135 / 95lbs
5 Shoulder to Overhead @135 / 95lbs
5 Burpees
Rest 2 Minutes
METCON for Time
Run 600m

Movements Completed by Catagory, (Gymnastics, Cardio, Weightlifting)

Movements Completed by Catagory, (Gymnastics, Cardio, Weightlifting)

Seconds Spent in a Heart Rate Zone (Full Class)

Seconds Spent in a Heart Rate Zone (Full Class)

Looking at the analysis of the workout, we can say that the days workout was very well conceived. We incorporated all three categories of movements (Gymnastics, Weightlifting, Monostructural) into our workout for the day. We warmed up with some dynamic flexibility movements an often overlooked but critical aspect of performance. We then practiced speed work for hang cleans which will definitely help us in future workouts. Finally, we went hard on some heavier weightlifting while also testing our aerobic capacity and recovery.

Something that most people will look at in this data and come to an erroneous conclusion is about the rest. If you look at my heart rate monitor it shows that I spent a large majority (2794 seconds) of my hour "Resting". This is a common criticsm of some gyms but in reality this is actually a sign that our coaches spent the time to explain the workouts, and gave us practice time to help us understand and improve, instead of the whole class going all-out for a full hour. If someone was looking for that kind of workout, then there are other versions of training that would better align with those goals. My opinion is I'm trying to get better at all aspects of fitness, and skill is a large part of this.


First we break down the workout itself. Below is a graph of my heart rate during the WOD, plus time spent in each zone.

Now we can tell I was working pretty hard. We defined the zones as multiples of twenty, (200 - 180 = Redline, 180-160 = Anaerobic... etc) For most of the workout, and even part of the rest, I was maintaining my heart rate in the "Anaerobic Zone", which is exactly where I wanted to be to move as fast as possible without burning out. You can see that I spent 132 seconds in the Redline Zone, which was on the final push for both parts of the workout. Using this information (and a few other statistics we can see that pacing does not seem to be an issue for me, at least in this workout. I did not redline too early and I was not taking it too easy (except in the very beginning it seems I tried to plateau for ~30 seconds at 165 bpm)

Seconds Spent in a Heart Rate Zone (WOD Only)

Seconds Spent in a Heart Rate Zone (WOD Only)

Heart Rate During the WOD

Heart Rate During the WOD


Something that really sticks out with me here is my recovery during the 2 minute rest. I wanted to see how fast and how much I was able to recover during that time, and the heart rate monitor data gives us the ability to do that. Lets put some numbers together that I can use in the future to calculate recovery time inside of a workout. Doing some very simple math, we can come up with a number that will help guide us.

Change in Heart Rate / Change in Time = Recovery Pace
180bpm - 135bpm / 346s - 428s = -0.54 bpm / s Recovery Pace

-0.54 bpm/s Recovery, or rounded to about 1bpm every 2 seconds of recovery. Now this number was a bit self selected, and there is definitely significantly more to look into here, but that would require a whole other set of analysis. The best we can do is verify that this number holds water by seeing how fast my heart rate recovered after the workout was over.

Change in Heart Rate / Change in Time = Recovery Pace
180bpm - 130bpm / 686s - 600s = -0.58 bpm / s Recovery Pace

So it seems that it is fairly accurate, although maybe we can attribute the extra recovery ability to all the lying on the floor complaining that I did after the workout.

Areas of Research

After doing this analysis, I have actually come out with more questions that I started with. Among them are

  • Why is there a slight pause before recovery? How log does that pause last?
  • Can I extrapolate workout output per BPM (kwH / bpm)?
  • During Recovery, there seemed to be a plateau at about 130 bpm. Why did that occur?
  • How does my performance match up against other peoples performance per heart beat?
  • Can I match up other statistics other than heart rate? (Pre workout feels, nutrition, blood glucose)

Hopefully I will be able to answer these questions later.