Do you know what MDR is?

[Morg]

Wow interesting graphs there jome.

Next time I am going to do some statics I will try and find a heart rate monitor and get some readings as well.

[naiad]

Originally Posted by jome

But, all that said, these facts remain:
-My best perfomances are done packing to the point of uncomfortable and relatively high heart rate (in the 70-80s vs 40-50s without packing)
-I still perform better in apnea on dry land
-Exception being deep diving, for which there is no way (?) to compare to dry apnea results, but there definately is a "jump" in performance (for example a 2 minute dynamic in the pool is torture, but 2-3 minutes in cw goes by like you don't even notice).

My best performances are done with full lungs and often a high heart rate. I perform better in apnea on dry land. I hope I will be better at deep diving than I am at dynamic.

[tylerz]

Most of my response here is targeting everybody and in response to many opinions I have come across. I am just working from some key statements Connor has presented.

Originally Posted by cdavis

I always thought MDR was pretty straightforward, mammalian physiology... <snip>... All divers experiance MDR (as I define it) whether they know it or not. You say you are not, but what's your definition of MDR?

Connor, good point that throws us right into the heart of the issue. MDR is frequently presented as an aquatic adaptation passed on from our ancestors (aquatic ape? other sea mammal?). Often, it is taught that we need to reengage or awaken the reflex in ourselves. This is suggestive of a reflex, as clarified by Ben Gowland in the original thread:

The term reflex should be reserved for an event which triggers a neurological or endocrinological response. If the 'reflex' is not 'controlled' by the body, and is a mere reaction/effect of pressure, then we decided that reaction was a better term.

Connor, what are you meaning by “straightforward” physiology? Are you referring to mechanical physiology as opposed to the involvement of the nervous system?

If one looks at the issue from the stand point of mechanical physiology, then we should be referring to the “diving reaction”. Further it seems largely presumptuous to refer to it as a mammalian DIVING reflex. Instead, in reference to Feign's post above, it could have been called the “birthing reaction”, or separated into “high-pressure reaction” and “hypoxic reaction”. At the time of first using diving reflex, I wonder if “facial-immersion reflex” was considered under the term diving reflex.

So, here we are with a term that in a minor way has had its use in the medical field, but it appears has not had enough attention or focus to really distinguish that there are multiple concepts and physiological systems at work, all being thrown under “diving reflex”. Not only does that cause a great ambiguity, but considering that the medical community goes to great lengths to separate and distinguish between the physiological systems, their workings, and interrelations, the “diving reflex” does not appear to reflect a mature concept. This suggests it has not been relevant or important enough to be repackaged and refined. To summarize some of the responses and reflexes suggested as covered by the MDR:

bradycardia reflex to apnea
bradycardia reflex to facial immersion
bradycardia in response to cold
vasoconstriction response to apnea
vasoconstriction reflex to apnea
vasoconstriction reflex to facial immersion
vasoconstriction in response to increased external pressures
vasoconstriction in response to cold
lowered cardiac output in response to core blood volume increases.

To summarize a few situations where at least one of these end results occurs:

life threatening bodily wounds
hypothermic conditions
meditation
yoga

If a person claims they are experiencing the MDR, it seems to suggest they are experiencing everything associated with MDR. It seems, MDR should not be referred to in the singular if a person is only experiencing a single physiological response that has come to be associated with the MDR. If MDR, as it's name implies, refers to a “reflex”, and only those responses which satisfy the term reflex, then a person claiming they have triggered the MDR, would be referring to triggering something in their nervous or endocrine systems. In this situation, referring to the MDR as a whole may make sense. However, if we are talking about mechanical responses/reactions, then referring in the singular to MDR suggests that all the responses are logically tied to each other, and unless impeded, will all take place upon diving, correct? Also, concluding MDR is taking place due to witnessing a subset of the responses occurring, whether diving or not, logically suggests that these responses are naturally originating from the need to deal with diving conditions. However, as we know, these responses occur in many conditions which have nothing to do with diving, therefore even though it is possible that diving conditions were the main push for such responses, it seems presumptuous to conclude it was so.

Packaging the MDR as all the things that we freedivers have come to associate with it, seems like looking at a human laughing, crying, bouncing about, heart-rate increasing, jaw muscles flexing, etc., from being tickled, and suggesting they are all responses originating and integrally owned by the “tickle reflex”. Of course these responses do occur in response to being tickled, but they occur in response to many things. Would it not be presumptuous to claim that these responses individually originated due to being tickled or some essentially equivalent situation? Does it seem realistic to suggest muscle growth in the jaw, an instance of crying, an increase in momentary heart rate, etc, all developed in the human body to deal with being tickled, or are a sign of an active “tickle reflex”? I wonder if this relation to MDR doesn't strike you as being a fair logical comparison?

So, I am inclined that MDR should more appropriately be used as a container to label what responses we “can” undergo as a response to diving conditions. That is what we do “know”. Science and the medical community attempt as much as possible to reflect what we tend to call knowledge. What we don't know is that the responses automatically occur when anybody dives, that the responses originate as an adaptation to water submersion specifically, or that the responses were not an adaptation to more prevalent conditions of mammals out of the water. Since we don't know that, I don't think the science or medical community would, or should, back a definition that suggests otherwise.

I went back and read some of the threads you referenced. Seems like some divers might be misidentifying some things as MDR(at least by my definition), but maybe. . . .

So, let's see some definitions that people think are appropriate for MDR?

To give mine, I need to specify that there should be at least two separate concepts we refer to:
MDR – a collection of reflexes in mammals that are known to sometimes occur in response to water submersion.
Diving Responses – a collection of physiological responses in mammals that sometimes occur due to water submersion.

Now, those are my choices of definition, but what not everybody may see is the degree of implication within each of those statements. There are implications of how to use the terms and what is covered by the terms. Statements, such as, "I felt my heart-rate drop significantly when diving the other day, therefore the MDR kicked in strongly," would not be a statement that could logically follow or take credence from my suggested definitions.

I tend to separate the physiological MDR response from the emotional, relaxation aspects but maybe that's not right. Is it possible that a strong physical MDR extends into the relaxation/emotional realm? or that either can reinforce the other?

Depending upon the definition, emotional may very well be part or not of MDR. It is all about definition and that is why I think there is so much confusion around the topic. It has not strictly been defined or where those definitions exist, too much imprecise extrapolation has occurred.

I am hoping that with enough participation here and promotion of clarifications that arise, our community can drive a set of definitions that are precise and accurate, which maybe will push the relevant fields to also eventually develop upon that need. As more freediving research occurs, it will happen anyhow. It would be nice if when that occurs, freedivers are not looked upon as having it all misconstrued and actively promoting weak reasoning and romanticism, for our own interests. The public currently receives its understandings mostly from the freediving community, therefore I believe we should be striving to be on top of things with a level of professionalism whether it benefits how we see ourselves or not.

Thoughts?

[cdavis]

Tyler, you think more deeply about this stuff than I do, part of why its fun to think about your posts.

To me MDR includes reflex and (as I understand your term) reaction, response. Its all the physiological changes that go on in the body that kick in when we start diving, get wet, hold our breath, etc. For me that would include dumping red blood cells into the bloodstream from the spleen, something most people might categorize differently. Thirty minutes into a diving session and my dives are approaching their best, I might say, " My reflex has kicked in all the way."
Not sure I understand your question about "straightforward physiology." Mechanical, I think. I readily see your point about fuzzy MDR definitions. I'm as guilty as anyone. It would be very useful to develop a set of well thought out definitions for all or part of the various diving related responses. Food for lots more threads in "Freedive Training" and better ways to better focus our training.

I agree with your points about the "aquatic ape" theory. Fun theory with some interesting supporting data, but I'm a bit sceptical. Maybe it is sufficient to explain MDR, but it certainly isn't necessary.

I am fascinated with the idea that MDR can include emotional reactions. Seems logical, given a proper definition, just never thought about it. Spearo background. How about expound on the ties between emotional and physiological responces the may or may not be associated with MDR type reactions. Anybody else??

Connor

[Ben Gowland]

Nice one Tyler - I barely remembered the original thread!

I still remember the issues surrounding Reflex versus Response/Reaction. Ironically, even within the scientific literature the two have been interchanged as if they are the same. I'd prefer to call it a Response as it captures all of the potential changes in the body. Although I believe there are some true reflexes there that have highly variable strengths between individuals and within individuals (depending on conditions).

But in the end so what - it is about maximising the response (reflex or not) so that we have great dives!

[Ben Gowland]

Naiad - do you pack (It would explain the high heart rates)?

[naiad]

I sometimes pack, but not always. My heart rate is high anyway. When I am doing normal everyday stuff, it is about 100. My lowest resting HR is 64, but it is normally 70-80 if I am relaxed and doing nothing.

[tylerz]

Originally Posted by Ben Gowland

But in the end so what - it is about maximising the response (reflex or not) so that we have great dives!

Not sure to what degree and what focus you meant to imply with "so what". However, to emphasize what I find important in working on this topic, the "so what" that I am working under are the following ideas:

1. Teachers only have vague, loosely interrelated, and inconsistent information to work from; creates a lack of confidence in presenting and elaborating this information.

2. Students put their trust in teachers, yet the topic in its unorganized and vague state, is arguably promoted as the most important topic to convey to students. This is fine if everybody is aware that this is the current state that the topic needs to be approached from, but instead this topic is taught as though there is a well defined and conclusive quality to it.

3. Because of its vague state, we see relaying of false/imprecise/inaccurate/inadequate information by teachers and students. This propogates exponentially.

4. promoting MDR at the forefront of our knowledge of freediving, yet, without any reasonably consistent or detailed comprehension of MDR, followed by lots of assumptions, weakens the stance that the freediving community has the ability to develop and discern relevant information. This can hinder the community from being taken seriously or professionally outside the community in this regard.

5. maximizing requires as much information as is available and drawing the relations between such information. Yet, if the information on MDR is not organized and clarified, then relations can not be drawn accurately and there is little ability to assess whether maximizing based upon currently available information is actually taking place.

6. if the information was organized and clarified then other previously unknown explorations and deduction may readily advance towards maximizing MDR.

So, at the end of the day, I see clarifying, organizing, and expanding on the concept of MDR as being the only way for freediving participants to collectively have access to digestible information towards "maximizing" MDR.

[oferdegi]

So, at the end of the day, I see clarifying, organizing, and expanding on the concept of MDR as being the only way for freediving participants to collectively have access to digestible information towards "maximizing" MDR.

I agree. One thing I can think of to promote the above stated objectives would be to propose and run some very simple experiments, conducted by as many DB freedivers as would be willing to cooperate in such effort. I'll leave it to you eggheads to propose such experiments.

Ofer

[naiad]

I would be glad to help out.

[Ben Gowland]

I see the problem within the 'Advanced' Freediving community in terms of accuracy of information, but:

The generally accepted definition (from Marine Mammal Science [MMS]) is not as defined as you think it should be. It is simply:- Bradycardia, peripheral vasoconstriction & 'blood shift'. Whether it is a response/reaction or a true reflex, or whether these are apneic or cold or pressure reponses/reflexes has never really been looked at in depth in MMS as it is not yet of much interest as they are still trying to study the magnitude of the responses rather than the controlling mechanisms.

Sadly science is too far behind the freediving world to be of much use to us.

[tylerz]

Good summary of the state of affairs outside the freediving community.

This state of affairs is actually fine. And only further supports what I am suggesting. Identifying what we do not know is knowledge in and of itself, therefore, is as important as specifying what we do know and what we suspect. It is how clearly, precisely, and accurately we identify and categorize the various points related to MDR that determines the quality of the information.

The quality seems to be low at this time. I am simply hoping we can take what we know, don't know, and suspect and form it into quality information.