HOW HEART RATE CHANGES DURING 2 DAYS OF QADA NAMAZ/SALAH PRACTICE. YEAH, I WAS CURIOUS.

Summary of this article:

1. Practicing qada namaz for 2 days puts you in Zone 2 training for the 80% of the total 33 minute duration.
2. Although we don't practice namaz for workout purposes, It is a valid Zone 2 workout when we practice daily debts from Fajr to Isha Vitr in order at a fast pace.

Two months ago, I have visited a sports physician with the complaints of not being able to get adapted to having exercises, even after 2 months of disciplined training. It is been more than 8 years, since I stopped exercising and I was having trouble to start back. No matter what I do, I always feel tired even with a good sleeping schedule, and couldn't find that adaptation where your body feels energized after getting used to some mid-levels of exercise.

After listening my complaints, my physician offered me a new training program circled around the heart rate monitoring and some additional flexing exercises. He told me to get a heart rate monitor and workout based on his suggested heart rate zones (mix of  140/bpm and 110/bpm and 90/bpm ranges). Later when I researched about it, I found out that these zones are pretty low heart rate zones for training actually, but thats a thing- It is called Low Heart Rate zone training and millions of triathlon athletes are following it.   
 
Long story short, I got Polar H10 heart rate monitor (considered as the most accurate one in the industry), along with a sports watch, and started my exercises. After about a week I felt pretty good about my progress, since the workout is not consuming me, I feel not tired at all, and after learning from triathlon athletes  who follow the Zone 2 Training for more than 10 years and completing a 42km run under 3 hours with a Heart Rate in ZONE 2, is just mind blowing to me. 

These learnings made me curious about one thing in particular, when I try to break even my salahs/namazs (reaching namazeven point), which is praying continuos qada namazs for the whole day from fajr to isha vitr in order. I feel the same way as I feel like practicing in light times in Zone 2 training (which is simply Zone 1 training ~ around 110-120 bpm). Therefore, I wanted to test it. I practiced 2 days worth of  qada namazs with a fast pace which is my normal speed of practicing namaz. It took about 17 minutes for me to finish whole days qada debt.

I used H10 on my chest strap during namazs, and one ceveat with that is: It could not pick up the hearth rate during bowing (ruku), prostration (sujud) and sitting (kade) positions. It was able to pick up heart rate correctly during standing positions though. This is considered normal, since the H10 strap is having space on the chest in those positions and can not pick up true heart rate. Therefore, I stood after each namaz to see whats the real heart rate reached while calling iqamah and noted them.   

My weight/height: 233 pounds/6'0" (106kg/183cm)
My normal daily activity heart rate: btw 65-80 bpm

Zone 2 is between 111 bpm and 129 bpm for myself.
Praying for 2 days qada:

Time: 33 minutes
Max Heart Rate: 123bpm

1. Although I have used the most trusted heart rate monitor, anomalities can be seen easily. It was not able to pick up heart rates except in standing positions.
2. Peak rates are gathered after each namaz, in standing positions where I was calling for ne iqamah for the next qada. This is surprising, cause indeed 20 seconds ago, I was sitting and in a resting position. This means that, my heart rate was indeed much higher during the namaz practice, but H10 could not pick it up. Even after sitting/resting position while I stand up, it picked up higher rates than it shown during the namaz practice. Therefore I will assume those peak values average are somewhat reality during the namaz. Therefore, average HR of 98 bpm is indeed misleading. The reality of average HR is the average of peak values.
These are my recordings in standing position after each namaz:

After practicing 1st Fajr Qada: 92 bpm
After practicing 1st Dhuhr Qada: 103 bpm
After practicing 1st Asr Qada: 110 bpm
After practicing 1st Maghrib Qada: 109 bpm
After practicing 1st Isha Qada: 115 bpm
After practicing 1st Isha Vitr Qada: 116 bpm
After practicing 2nd Fajr Qada: 115 bpm
After practicing 2nd Dhuhr Qada: 111 bpm
After practicing 2nd Asr Qada: 118 bpm
After practicing 2nd Maghrib Qada: 118 bpm
After practicing 2nd Isha Qada: 123 bpm
After practicing 2nd Isha Vitr Qada: 111 bpm

Average Heart for first 20 rakats of Namaz : 108.6 bpm
Average Heart for last 20 rakats of Namaz : 116.2 bpm  
Average Heart for whole 40 rakats of Namaz : 112.4 bpm 
(All of these above rates calculated with weighted average of each namaz rakats)

This value 112.4 is within the lower threshold of Zone 2 activity zone. Zone 2 is well known for its long term benefits such as: 

You can learn more about Zone 2 training here if you like.
I don't want to go into details of Zone 2 training here, since I am also just learning about it, but you get the idea. It is a lightweight training, that yields a massive benefit to our physical and mental health. Lets see how namaz aligns with it. Of course we don't practice namaz cause we want to workout in Zone 2, however while we are paying our qada namaz/salah debt we might just do ourselves a huge favor without even noticing.

Keep in mind that Zone 2 training is suggested for 20 minutes for beginners and, gradually work your way up to 60 minute workouts. This means that for qada namaz's you can start with 1 day of debt and up to 3 days of debt paying in the long term. 

Also, there are different methods about deciding on Zone 2 levels, since using 220-age formula for highest heart rate is an estimate, there are healtier ways to determine this value (metabolic test, talk-test, and lactate test), and you can do so but I am good with this approach as a beginner.