1. We tracked heart rate variability in college football players from day 1 of preseason training through to the national championship. Some key findings & thoughts discussed in the thread below.

Tweaked my back a few days ago making the age-old mistake of lifting too heavy in the morning when I’m an afternoon lifter. Rx = body weight training as tolerated, AE, and stretching. Feeling better and HRV coming back up.

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Garmin 2-min Health Snapshot vs ECG. - 3 seated, 1 standing. - Clean samples (all normal beats). - No filter, no detrending. RMSSD difference <3 ms (range 0.2-2.8). SDNN difference <1 ms (range 0.1-0.6). Will see how it performs with higher/lower values, diff skin tones this

Oura ring is probably the most accurate wearable on the market for HRV. Nevertheless, this new figure shows that its agreement with Polar H10 decreases at higher RMSSD values. Strong agreement until ~60 ms, then difference scores spread.

Confirms my suspicion.

This figure from a new study shows very clear proportional bias by Garmin. It’s underestimating high HRV values and overestimating low values. Looks like this affects values <40 and >60 ms. Use with caution and note that these still aren’t research tools.

Dose response effect of alcohol intake on HR and HRV. Up to ~37 bpm increase in HR. Up to ~25 ms decrease in RMSSD

Macro-level vs. micro-level data-guided training example. Standing HRV peaked at the end of summer break (pic 1) then crashed last week with start of the semester (pic 2). Full trend in pic 3. Thus, for optimal cardiovascular health and training response, I should quit work.

I’m a big fan of the convenience factor but it needs to be used with caution. This method can be accurate (pic 1) but it’s not always accurate (pic 2, bottom left panel, shows greater error with higher values). I’ve struggled with consistent clean measures since the newer

New meta-analysis shows that higher cardiorespiratory fitness lowers mortality risk across all BMI categories, while low fitness increases risk regardless of BMI (pic 1). One possible unmentioned mechanism could be better autonomic regulation with greater fitness, reflected in

Three recent studies suggesting that resistance training alone isn’t good enough. If someone tells you not to do cardio, run away. And keep running for ~30 min. You’ll escape the bad advice and get your much-needed daily AE.

7/ . Final Takeaway. There was a tendency for greater cardiac efficiency during exercise when standing HRV was higher. There was a tendency for greater internal load in response to a fixed stimulus when standing HRV was reduced. Considering that I cannot use sleep HRV to.

6/ . Standing HRV helps avoid saturation. This is why the original HRV-guided training studies (Kiviniemi et al. 2007, 2010) used standing measures. If your HR is <55 bpm, I would strongly encourage you to create a scatterplot of your HR and HRV to determine if this affects

5/ . Why Sleep HRV Failed. My sleep HR was consistently <55 bpm. At low HR, parasympathetic saturation can occur. Note that the association between my RMSSD and HR is negative in the standing position (as HR goes down, RMSSD goes up, expectedly), whereas the opposite occurs for

4/ . Correlations with HRex. Sleep HR: r = 0.58 (strong, in expected direction) indicating that when sleep HR was lower, HRex also tended to be lower. Sleep HRV: r = 0.25 (small, in opposite direction) indicating that when sleep HRV was higher, HRex also tended to be higher.

3/ . Trends Over Time. HRex tended to ↓ across time, consistent with improving fitness. Sleep HR tended to ↓ across time, consistent with improving fitness. Sleep HRV tended to ↓ across time, inconsistent with improving fitness. Standing HR tended to ↓ across time,

2/. How did I do it?. All tools used for this self-experiment were wearable devices that I validated on myself. HRex = avg HR from last 3 min of a daily 20-min treadmill walk at 3.7 mph, 1.5% grade (50-60% HRmax) measured with Polar Vantage V3 (validation in pic 1). Sleep values

1/. Summary thread of recent n=1 HRV experiment. Link to full blog at the end. What did I do?. I compared associations between my daily submaximal exercise heart rate at a fixed intensity (HRex, an indicator of aerobic fitness) and both nocturnal and standing RHR and HRV over a