• Welcome to the DeeperBlue.com Forums, the largest online community dedicated to Freediving, Scuba Diving and Spearfishing. To gain full access to the DeeperBlue.com Forums you must register for a free account. As a registered member you will be able to:

    • Join over 44,280+ fellow diving enthusiasts from around the world on this forum
    • Participate in and browse from over 516,210+ posts.
    • Communicate privately with other divers from around the world.
    • Post your own photos or view from 7,441+ user submitted images.
    • All this and much more...

    You can gain access to all this absolutely free when you register for an account, so sign up today!

Differences in bpm during static

Thread Status: Hello , There was no answer in this thread for more than 60 days.
It can take a long time to get an up-to-date response or contact with relevant users.


Oct 16, 2001

I would like to hear if someone has any experience in this matter:

Me and my buddy trains static once a week and we always measure heartbeats per minute during the sessions!
The strange is that our bpm pattern totally differs. :duh (maybe it's not strange for some people who understands it)

His pattern is something like this:

5.30+ -----30bpm

My pattern is this:

Our pb is both a little more tha 6min.

He has no contractions but I have 40-45 during a 6min breathhold (starting at around 3.50).

As you can see his heartrate goes down more than 50% and my drops around 22%.
Can it be different alkalinity of the blood, different initial CO2 or simply that he has a very strong diving reflex and I have not?

both of us pack around 6-8 packs.

My rest heartrate is about 48 and his something around 42.

Does anyone have a clue?

Can we learn something or is it unexplainable difference in physics?
Very interesting

That numbers are quite interesting.
My patters is similar to the first apneist and my brothers too.
The interesting part of this is the apneic times.
Let me squezze my brain for a while and let you know my thinkings about it
What is important is not the heart rate, but the 'double product' = systolic blood pressure x heart rate. The 'double product' gives you a more accurate indicator of cardiac O2 consumption. Even then, stroke volume is different.

Martin Stepanek, for his world record-level statics, had a heart rate of about 105 until 4'00, then when the contractions began, it would drop to 50-55 for the rest of the breath-hold.

In my case, I start around 100, then gradually drop to about 55 at the end.

Eric Fattah
BC, Canada
Eric, out of interest, what's your resting hr? My hr during statics seems to be a bit different from that - in the first few seconds it'll drop significantly (like 30%), then slowly build up until half way through contractions it's fast, then slow off again. So over 4 mins something like:

0sec: 70
5sec: 45
1:00: 50
2:00: 60
3:00: 75
3:30: 60
4:00: 55
Eric your answer is interesting, I know for a fact that I have a very low blood pressure maybe because I was a junior top level cross country skier and still are fit cardivascular? (VO2max about 80 then, but that was 13years ago).
It would be interesting to know the exact numbers for both my buddy and me but I just remember that my bp was low when I measured it.:confused:

I'll wait for your thinkings fpernett
Cardiac output

First than everything, it has always been considered the bradycardia like a strategy of our body to save oxygen. And in fact most of carried out studies both in hyperbaric chamber as in the sea have demonstrated a bradycardia (low heart frequency) induced by the immersion. But more than just the bradycardia is important to remember the Cardiac Output. This is the product of multiplying the systolic volume (the quantity of blood that eyects the heart in each contraction) for the heart frequency. By impedanciometry methods the systolic volume has been measured and it has been shown that it doesn't change along an immersion simulated in a hyperbaric chamber. And as always a bradycardia has been observed it is considered that the Cardiad Output diminishes during the immersion. An indirect form of measuring the systolic volume is the Systolic Arterial Tension (as Eric said it) and it will be an indicator a little coarse of our systolic volume, I said coarse because the SAT doesn't depends only on the ejection volume.
For the apneist in immersion, a reduced Cardiac Output is not always a problem, since the flow strays preferably to heart and brain, and not to the whole body.
Our body has pressure receptors, and if there are decreases of the SAT, this would avoid in certain way the extreme bradicardia, because it could commit the Cardiac output.
The experiments of the Dr. Ferrigno with Enzo Majorca and Rossana Majorca in hyperbaric chamberswas carried out with direct mensuration of the blood pressure and they really observed an increment in the BP with values of SAT that arrived to the range of 290 mmHg, but this was like simulating a No-limits immersion , as far as I know there is no trial where the BP was measured in static.
It will be good to know the BP at rest and during the realization of static apnea among both to have some clarity.
Hope I spell my thinkings well
  • Like
Reactions: derelictp

I am not sure if I understand this correctly.

Systolic blood pressure is constant?
By impedanciometry methods the systolic volume has been measured and it has been shown that it doesn't change along an immersion simulated in a hyperbaric chamber.

QUOTE]What is important is not the heart rate, but the 'double product' = systolic blood pressure x heart rate[/QUOTE]
This determins your O2 consumption which should be constant in statics. Then your HR should be constant too.
Or am I missing someting. :confused:

Your O2 consumption is definitely not constant during statics. As the static progresses, your BP increases, your HR decreases, in such a way that the net effect is a gradual decrease of O2 consumption rate.

Eric Fattah
BC, Canada
Hi Zipy,
The systolic volume or stroke volume is the amount of blood ejected in every contraction. It's not the same than systolic blood pressure. As Eric said, the BP increases during apneas


After reading both Erics and Franks answer the conclusion to this maybe that what determines cardiac output from the heart is:

1. Heart rate
2. Bloodpressure (systolic)
3. Stroke volume (systolic)

And I can say that I can feel my heart beating very "light" (not powerful) during breathup and static compared to normal.

The next question is why does the heart behave this way, is it because the blood is alkaline or is it because of a lowered metabolism that makes the heart beat different because it's energy saving?

In static it seems to me that 2 things affects my heartrate.

-Lowered CO2 levels seems to increase the heartrate.
-Packing seems to increase the heartrate. (Empty lung static seems to reduce heartrate radically)
Cardiac output

Just to make it clear:
Cardiac Output = Stroke Volume * Heart Rate
An the stroke volume depends on :
Preload = The amount of blood that arrives to the heart. If you are dehydrated less amount of blood will arrive to heart and it afects Stroke Volume
Postload: It's what the heart has to pump against, like blood pressure. If you suffer hypertension, the heart has to pump against you higher pressure. It affects the stroke volume too.
Contractility: Is the strenght of miocardial muscle to contract. If a person have suffer an infarction and has some "death" muscle his Stroke Volume will be afeccted.
All this means that Heart Rate, Preload, Postload and Contractility will affect the Cardiac Output.
On the other side the acid blood will produce vasodilation and lower the contractility of heart muscle. The alkalinity will affect the conctractility too, and diminish the Cardiac Output, makes the heart prone to arrythmyas and lower the K+. Of course it depends on how you get to that alkalinity it's different if it's a respiratory alkalosis or a metabolic. Hyperventilation produces respiratory alkalosis and the kind of diet can produce metabolic alcalosis.
There is any important difference in BP, respiratory pattern, food habits, and age between you and your partner?
The food habits for me and my buddy does not differs much.

I'm 35 years and my buddy is 25.

I don't know about differences in bp but I will try to find out!

We both use a method of breathup that is very relaxed but I can't tell if it differs. The best way to tell the differences here would be to measure CO2 levels?

Anyway thanks for good thinkings!! :)
  • Like
Reactions: fpernett

The age could be a difference.
I read an study of Erika Schagatay where the heart rate was compared among different class of divers (UW rugby players, Japanese AMA's, Indonesian tribal divers, etc) they found that diving bradycardia was higher in Indonesian and UW rugby players, the diving bradycardia was almost nule in the AMA group, but the mean age of that group was 54, indonesian was 30 and UW rugby players was 25.
They found a blunted diving bradycardia in Japanese AMA. The heart rate in apnea was similar to non-diving controls.
This is not your case because the age difference between your partner and you isn't significant.
Another question is the experience in freediving? Both of you have the same time practicing apnea?
The parasymphatic tone is different among people, and this can explain the difference.
The thing that's more interesting to me is that both of you have similar apneic times, and some have said that diving bradycardia is an oxygen saving reflex. But this doesn't seems to be that case.
Eric, have you measured your heart rate in your maximal static time? It will be good to find out differences in heart rate with PB in static time. But I'm not sure of it
Last edited:
Interesting study!

Me and my buddy have both some years of training behind us.

I began freediving in -97 and my buddy have at least 3 years of training.

I agree about bradycardia saving oxygene. In Peter Lindholms research he shows that.

The problem whith such studies is that it's hard to isolate only bradycardia vs cardiac output because there is other factors that also makes a difference in cardiac output, for example relaxation.
That's the point

That's what seem interesting to me, if we think in bradycardia as a preserving oxigen reflex, your apneic times should be less than your mate.
We have to take in account the oxygen comsuption rate.

I don't think that the relaxation affects the Cardiac Ouput directly, but it should affect the consumption rate.

As you mention it, the main drawback in all the studies, is that is diffucult to calculate physicologycal variables.

Some have said that is better just take in account the "easy phase" of apneic time, because the "struggle phase" is more prolonged in trained apneists.

I'll check this weekend BP and HR while doing static with my mate to see if I found differences, I'll try that my brother make the same
heart rate drop at end of static

My heart rate does this -

First part of static - quite violent drop (presumably due to immersion reflex), then stays low then goes up a bit around first contraction but the weird thing is that on PB attempts it always drops again, quite dramatically, just before I give up and surface.

My buddy thinks this may be what is triggering me to give up? and presumably if I can get used to to it I could stay down longer. (We are not seeing the same effect on tables or times I know I can comfortably do.)

Anyone reckon this is possible? I never really know why I come up for air, just a general panicky feeling. Until now I had interpreted this panic as an approaching samba... Does anyone know if the heart rate drops right down before samba/blackout? (we haven't had the monitor on at the right time to see that yet!!)

One Canadian diver who had never had a samba/BO in static, wanted to learn what the warning signals were, so he told his buddy; "I'm not comin' up from this one. Drag me out when I B/O." So, he started his (wet) static. As the contractions intensified, he kep telling himself, 'I'm not comin up,' and around 5'30 he tensed up, then exhaled and went limp, and blue, motionless. His buddy dragged him out. He learned the warning signals. He didn't have any sambas/BO's after that.

Not necessarily the recommended method though.

Eric Fattah
BC, Canada
HR monitoring during statics

I usually monitor my HR with my Polar S610. The great thing is that you can analyse the results on your pc afterwards :D

When the first feeling of discomfort appears (I never have contractions:confused: ), I push the "laptime" button. This way I can separate the comfort zone from the struggle phase.
Almost all statics have the same pattern: it starts with a high HR of about 90, then drops within 30 secs to about 60. Immediately when the first feeling of discomfort appears, the HR drops very slowly but steady to about 45.

Fred S.
I only have a very simple POLAR A1:waterwork

Fred, I belive your pattern is the most common.

To other strange things I have noticed:

When I measured the heartrate on an apnea while on a trainingbike I had the following data:

Before apnea----140bpm
at 1min apnea---52bpm

My bradycardia seems bigger at apnea+work than apnea+rest.

Another thing:

When I dive in the summer I do hangs at 20-25m and when I count my heartrate it seems to be lower than 30bpm but the heartbeats are very strong. I can almost hear them:D .
That's strange.... (however I can only compare this with my own patterns..)

In the gym I like to do apnea training on a bicycle as follows:

- a total training time of 36'.00" at about 140 Watts resistance
- a constant 75 rotations per min. during the whole session
- 3'.00 warm up (no apnea)
- 30 x (30 secs apnea / 30 secs breathing & recovery)
- 3'.00" cooling down

During this training my HR is usually around 140 but never below 120 or even 51 like you had. But I must add that I have a rather high HR compared to others.

Fred S.
  • Like
Reactions: derelictp
DeeperBlue.com - The Worlds Largest Community Dedicated To Freediving, Scuba Diving and Spearfishing


ISSN 1469-865X | Copyright © 1996 - 2024 deeperblue.net limited.

DeeperBlue.com is the World's Largest Community dedicated to Freediving, Scuba Diving, Ocean Advocacy and Diving Travel.

We've been dedicated to bringing you the freshest news, features and discussions from around the underwater world since 1996.