Monthly Archives: April 2015

Heart Rate Belts, Phone Cameras and Convenience

I had a chance to have a coffee with Marco Altini, the builder of the Heart Rate Variability Logger app that I often use to take readings. I enjoyed the discussion as Marco is very knowledgeable on the topic of heart rate variability. I took some key insights away that will help me set direction for future studies.

During the discussion he told me he is focussing on his app that support physical training, HRV4Training. He prefers to work on this because in addition to a bluetooth heart rate belt the user can choose to take a reading with the camera on the phone. Marco thinks that the convenience of using the camera makes it more accessible.

I agree with him. In my own work I often to not take advantage of readings because I don’t have the belt on and simply don’t feel like putting it on. Just this week I did one reading while conducting an interview using the belt, and I did not take readings on numerous meetings that would have given me good data for further study.

And while pushing into new areas of study such as heart rate variability during negotiations, or while giving a speech, it is not going to work to have a finger on a smart phone camera. To only use the camera would confine readings to stationary sessions where no activity was allowed. There is much more to learn than taking readings in only a motionless state.

So I am going to start incorporating smart phone camera useage into my work and share the results here. Marco has done a workup of how his apps use the camera to compare well with the Polar H7. We have to figure out a way to make this accessible, and useful, so more people can train for improved personal performance using heart rate variability.

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Superpower Series: Introduction

Our strength as a species that can envision a potential future is also the source of our greatest perceptual error. We tend to freeze a picture in place as a goal and once a situation is to our satisfaction we will want to maintain that situation frozen permanently.

This mechanism is effective when we want to achieve an outcome. We see something we want to build in our minds and keep it fixed until we see the outcome achieved. This same mechanism backfires when we try to freeze a situation in place despite it being dynamic by nature.

When we picture relaxation or stress reduction, we picture permanent relaxation frozen in time. Our expectation is that we will enter a permanent state of enlightenment where everything will be calm and ok from that point on.

Our work here is about finding the variability in our physiology so we can compare it to external circumstances. We naturally physically accelerate and relax as we go through life. These up and down reactions can come from our circumstances, or it can come from our imagination. When we are reacting to our circumstances we are in alignment with what is real and reacting appropriately.

When we react with our imagination we can be reacting to fictions, and fictions can make us accelerate when it is not necessary. So our goal is not to dumb down our accelerations or artificially amp ourselves up, it is to accelerate when circumstances call for it and to rest when no acceleration is needed.

If you want to learn more about developing a Superpower read about Basic Training.

Superpower Series: Variability Basic Training

Before you begin taking readings in work sessions and meetings you have to become familiar with the pattern and connection between your circumstances, Heart Rate Variability (HRV), and breath. Your breath rate signals to your nervous system whether your circumstance calls for an accelerated state, or a relaxed nervous state. Conducting repeated sessions will allow you to see the relationship.

Exercise: Using basic kit take a measurement each morning for five minutes. While doing so, breathe six times a minute. That means breath in five seconds and out for five seconds. You can start with a smaller period if you are uncomfortable  and need to practice. Even at smaller intervals make the breaths even and consistent. Afterward look at the intervals between heart beats to see how well your breath and HRV relate to each other.

If you are relaxed the measure of RR intervals will go up and down evenly with your breath. This means your Parasympathetic Nervous System (PNS) is applying the brake to put you in rest and digest state. Here is a graph of my RR intervals during a five minute session in a completely relaxed state:


I have had many sessions where despite regular breathing I could not enter a relaxed state. Here is a session where I was thoughtful about a variety of to do’s while trying to bring myself to a relaxed state. These Upsets were evident in the graph of my RR intervals:

You can see in the intervals have periods where there is not much variability. My thought process was accelerating my Sympathetic Nervous System even though I was sitting quietly breathing in a regular rhythm. In another session I was generally relaxed and in the zone then had a thought that interrupted my flow. I let the through go and returned to breathing and recaptured my variability. You can see the interruption and return in the red circle.


In another session on two occasions I had Upsets in the flow of the session and was able to recover twice. You can see these episodes in the red circles in this chart.


The exercise of breathing regularly and taking your HRV measurement for five minutes a day will give you a baseline for when your system is Upset by different thoughts, and when it is responding to your breath while relaxed.

If you want to learn more about developing a Superpower read about Giving a Speech.

Why Apple Watch Will Not Be Accurate on Stress Readings

With the imminent launch of the Apple Watch it is clear that everyone is looking to it for new functionality and inevitably there will be claims you can reduce stress using it. I wanted to look into whether the device could reliably deliver on that promise.

Apple Watch Will Not Be Accurate

The watch reportedly can read heart rate by taking pulse readings from the wrist using pulse oximetry, a method that uses light pulses to read heart beats by measuring the change in skin color due to different levels of blood flow. Pulse oximetry is refined enough for reading heart rate, but Heart Rate Variability (HRV) demands precision that pulse oximetry reportedly cannot deliver.

I am interested in using HRV to improve personal performance in working sessions, face to face meetings, negotiations and public speaking. I thought it would be interesting to be able to use an Apple Watch to read HRV and improve those skills. So I wanted to test pulse oximetry myself.
Apple Watch Will Not Be Accurate

I don’t have an Apple Watch, so I connected a Mio Velo wrist worn band to the SweetbeatLife app on an iPhone. The Mio product claims to deliver “EKG-accurate heart rate data” and uses pulse oximetry, so this would be my proxy for an Apple Watch.

Apple Watch Will Not Be Accurate

To compare this setup with readings from electrical signals I connected a Polar H7 to Marco Altini’s Heart Rate Variability Logger on an iPod Touch. This would allow me to take two readings of a single heart beat and compare the methods. After wrangling settings and conflicting signalling I got them both to work.

My goal was to use my Parasympathetic Flatline method when comparing the pulse oximetry with electrical readings using a heart rate belt. This means I am looking for 10 consecutive heart beat intervals that vary less than 17 milliseconds from beat to beat. When I find these strings of beats I am measuring myself in a fight/flight state.

Researching pulse oximetry I found a research paper that said that physical movement introduced errors in readings making pulse oximetry unreliable for measuring HRV when subjects were in motion. The conclusion was that pulse oximetry “is unlikely to prove a practical alternative to the ECG in ambulatory recordings or recordings made during other activities.”

Apple Watch Will Not Be Accurate

My interest is looking at activities like negotiating, meeting and coding where there is not a lot of physical movement. With the study providing some potential for pulse oximetry to provide some value to my area of interest, it seemed reasonable that readings when relaxed would be similar and when walking very different.

I conducted sessions in a relaxed state, working by myself on the computer, in meetings and while walking. I first conducted the dual measurements while in a relaxed state for ten minutes. I sat and did not move and breathed in an even rhythm. Subjectively I think I was in fight/flight for 25% of the time because sitting motionless allowed me to think about all the things I was not getting done. Here is a graph of the two readings:

Apple Watch Will Not Be Accurate

The pulse oximetry reading was that I was in fight/flight 87% of the time and that is way overstated. The P7 said 32% and that was much closer to my experience. So the relaxed state had a completely different outcome than my hypothesis.

Next I measured myself when I was in a working session, which meant I had structured some time to work on my computer without interruption. I was working on some recruiting matters which meant screening resumes. It was very focused work and I felt relaxed. I would have said I was 10% at most in fight/flight. My session was 16 minutes long, and here are the charts:

Apple Watch Will Not Be Accurate

The pulse oximetry reading said I was in fight/flight 57% of the time. This did not remotely match my experience. The H7 reading said I experienced no fight/flight at all. There were accelerations, but none that were more than 9 beats. So though I’m not sure it was a perfect session it was clear that the H7 more closely matched my experience.

I also took readings during the first and second half of a long staff meeting. I was not the host, I was a participant. There were some controversial things being discussed so I would have subjectively said I was in fight/flight 15% of the time. Here is the chart for the first half of the meeting:

Apple Watch Will Not Be Accurate

You can see the pulse oximetry said I was at 62% fight/flight, H7 10%. Here is the chart for the second half:

Apple Watch Will Not Be Accurate

Pulse Oximetry had me at 63% and H7 at 1%. The H7 seemed low because there were a few moments where I was definitely in a heightened state, but an average under 10% is much close to the perceived 15% than a consistent reading by the Apple Watch equivalent of over 60%. That just made no sense.

I took measurements while walking. I had low expectations because I had taken readings when exercising and know that HRV is low when physically active. Here is the chart as I took my first walk to the train from work.

Apple Watch Will Not Be Accurate

I walk briskly so I expected a 60% to 75% reading here. What you see is Oximetry at 91% and H7 at 67%. Again oximetry was high. Here is my reading for leaving the train and going to the pickup point:

Apple Watch Will Not Be Accurate

What is interesting here is my wife picked me up about a third of the way through the reading and I relaxed in the car chatting with her as she drove me home. The H7 clearly shows me moving from an accelerated state to more relaxed, which was my experience. The oximetry reading shows continued stress. Again the H7 reading matched the experience.

So what conclusion can we draw from comparing pulse oximetry as used by Apple Watch to electrical readings from chest worn heart rate belts? In the range of activity from sitting motionless to walking briskly the pulse oximetry method overstates stress.

So your Apple Watch is not the best tool to measure stress response using HRV. When you read, “Physicians and digital health experts are encouraged by the level of accuracy suggested by the Apple Watch’s sensors,” remember that pulse oximetry will overstate your stress. In a world of stress the last thing you need is to have it overstated.

Superpower Series: Why You Should Memorize Your Speeches

One superpower that some people seem to have mastered is the ability to stand in front of a group of people and give a speech. For most people it is the most stressful of events, up there with losing a job and divorce. So how can you use Heart Rate Variability (HRV) to keep your fight or flight mode from kicking in and you entering a panic state in front of the group?

Well, it does not appear you can avoid the fight or flight response standing in front of a group of people. From measurements I have taken when speaking I think that the only strategy you can employ is to have more material embedded in memory so you just speak automatically without having the engage your prefontal cortex.

The mechanics of this are straightforward. When you are in fight/flight your body optimizes blood flow to get you out of danger. Blood flows to your limbs and the back of your brain, allowing you to maximize your ability to react. When you are in this reaction mode your thinking brain is offline. You can’t wing it when your thinking brain is offline.

I took readings while speaking at two different Quantified Self meetups. This is a very sympathetic crowd. There is no pressure to perform for this crown. And I have experience speaking publicly, from corporate engagements to speaking competitions for Toastmasters. I enjoy public speaking, so I should be on the more relaxed end of the spectrum. The data shows that even experienced speakers are not immune to the stress of presenting to groups.

As a baseline for compare readings from a meeting with senior people that I am working for as I presented in an earlier post. This was a high intensity meeting where I was expected to present information. The graph shows with blue bars where I experienced the fight/flight impulse.

Readings on a speech I did at the meetup July 28th of 2014 showed how much stress the system kicks in when on a stage. I started the measurement about five minutes before the speech and did some breathing exercises to see if that would have an effect on my measurements. Here is me giving the speech.

Qs Speech

The breathing exercises did help kick in my relaxation response for the first five minutes of the reading. Once I got to the podium, however, the fight/flight kicked in. I spoke for 14 minutes and answered questions for ten minutes. You can see the readings in this graph: The red box shows the period in which the speaking portion of the presentation took place.


A second speech showed a similar pattern. In March of 2015 I spoke again at a Quantified Self meetup to a smaller group. Again a very sympathetic group. I knew the material and was pleased to be presenting. This was a shorter speech, five minutes speaking and five minutes of Q&A. You can see from the chart and the red box that the during speaking portion I was almost entirely in fight/flight state.


Why this is important is  as described above the pre-frontal cortex is offline when in this state. Meaning that you can’t think through what you are going to say in real time when you are on the podium. You are in reaction mode. So rehearse the material. When a slide comes up, you react to what you have memorized. I have had experience of “watching” myself giving a speech when I have memorized the material and am bouncing along well. And I have had the experience of freezing in place when I had nothing in my deep memory to react to. And I just stared blankly at the audience.

So memorize your material before you get up to speak. Your physiology will ensure your brain is offline. If you react well throughout the speech you will give a great speech. Even this guy had to memorize his speech: