Yoga in the morning or evening? And how do I compare with a military guy?

This is bit of a fun little experiment I did with a friend. It’s a comparison between two people and a comparison within the same person. The ashtanga series is a complex set of moves and I wanted to ask two questions:

  • How different or similar are the heart rate profiles between two different individuals?
  • How different or similar are my own heart rate profiles when I practice in the morning vs. the evening? In other words, how much does the time of day matter?

Study participants: De-identified person 1 (CD) and de-identified person 2 (SquirrelB). CD is male, and a highly trained and very fit military dude. Me, SquirrelB, I’m lay-person (no military or sports training) but okay-fit for my age group and profession.

Study design: Record my heart rate during evening yoga practice and during morning yoga practice. Then use the same measuring device (my Fitbit Charge 2) that’s calibrated to me and let DH wear and record his heart rate during an evening ashtanga practice.


CD exhibits a much lower average heart rate than SquirrelB throughout the practice. This could mean that CD has better physical conditioning, and some of the strength moves may be less strenuous for CD than SquirrelB. However, the overall profile and fluctuations in heart rate during the series appear very consistent between the two individuals.

Heart  rate profiles over the course of 65 minutes of yoga in two individuals (CD: male, very fit; SquirrelB: female)



The surprising finding… I am less similar to my own self than I am to CD depending on the time of day. Sorry if that’s confusing. What I mean is, my cardiac profile during ashtanga in the morning vs. the evening (i.e., the intra-person correlation) is more dissimilar that the inter-person correlation in the evening.

Pearson correlations between SquirrelB in the evening vs. SquirrelB in the evening (Top); SquirrelB in the evening vs. CD in the evening (Middle); SquirrelB in the evening vs. SquirrelB in the morning (Bottom)


So if I compare my heart rates from two different evening practices, I see a strong correlation with Pearson R = 0.76.



The linear correlation between CD and SquirrelB’s evening practices is also very similar with Pearson correlation R = 0.62. This is despite the fact that when CD got his heart rate recorded, we had a different teacher and therefore slightly different pace (and no handstand practice).


Compared to that, the correlation between SquirrelB’s morning vs. evening practices is R = 0.58, which is the lowest correlation in all the comparisons.




The time of day appears to be a very big factor on practice intensity and heart rate profile. Subjectively, I’m not too fresh in the morning and I exert myself a lot less.

So is it better for me to practice in the morning or evening?

I think I gain a lot more practicing in the evening since I’m able to go deeper into poses and able to do the vinyasas with more vigor and enthusiasm. However, a morning practice may also come with its own set of benefits that I may not get from an evening practice since my physiology is somewhat different then. I think I’ll continue to stay more committed to my evening practices, but also try to make it to more morning classes.

[please excuse typos and errors; not proofread and author makes lots of typos]


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