Looking for fitness information

[frankencrank]

When you folks say CO, I assume you mean CO2.

Basically, this entire thread is navel-gazing. There are many epidemiologists and public health professionals who are interested in this problem, and I don't think that "institutional review" or cardiologist complacency is the major impediment to predicting health outcomes from measures of fitness.

My impression -- and this is just my impression that you can refute with properly controlled study results -- is that health outcomes improve dramatically with some level of fitness, but not particularly with athletic levels of fitness.

CO means cardiac output. Sorry for the jargon and shorthand.
Go back and read the linked study. Risk of dying increases as ones exercise ability decreases below "normal" and decreases as ones exercise ability increases above normal - measured in mets on a stress test. That is considered a measure of aerobic fitness.

[frankencrank]

My impression -- and this is just my impression that you can refute with properly controlled study results -- is that health outcomes improve dramatically with some level of fitness, but not particularly with athletic levels of fitness.

Risk of dying decreases the higher your aerobic fitness. That is clear from the study I linked.

The question you might want to ask yourself would be: Where do I fall on this spectrum?

The purpose of my idea is to, hopefully, answer that question for you without you needing to jump through a bunch of stuff.

[Carl Watts]

Some people here are seriously over thinking things and have disappeared down the rabbit hole.

Once you decide you do not want to be a couch potato your whole life and start some regular exercise all your interested in how you are placed against the general population not elite athletes

If you can hit 75th percentile or better I don't think you need to worry about the state of your fitness.

[Mike Caviston]

You might want to check your data.

You might want to check yours. For somebody who keeps claiming to be an expert in physiology, you keep bungling some pretty basic concepts.

Resting VO2 is about 250 ml/min in a 70 kg man.

And 70 kg x 3.5 mL/kg comes out to about 250 mL per minute! You really don't understand relative vs absolute VO2?

At exercise that man can burn 5-6 L/min.

For a 70 kg man, that works out to about 70-85 mL/kg/min. Not impossible, but at the upper end of human performance. Incidentally, that works out to 20-24 METs.

Oxygen carrying capacity of the blood doesn't change.

Who said it does? Why is that relevant?

If CO can only increase 4-6 times then the max mets possible would be 4-6 and we would all be striving to get to a 10 hour marathon.

This part really gets me, to the point where I think you must be trolling. Seriously, please quote some values for resting and maximal Cardiac Outputs. I still want to see where you are coming up with a 20-fold increase.

The met is what your body is receiving and using at rest. I believe it a safe assumption that whatever your HR is at rest it is delivering exactly 1 met.

Yes, as I said previously, one MET equals the resting VO2. Since resting HR varies so much within and between subjects, how can you possibly use resting HR in any calculation to estimate max METs?

[frankencrank]

You might want to check your data.

You might want to check yours. For somebody who keeps claiming to be an expert in physiology, you keep bungling some pretty basic concepts.

Resting VO2 is about 250 ml/min in a 70 kg man.

And 70 kg x 3.5 mL/kg comes out to about 250 mL per minute! You really don't understand relative vs absolute VO2?

I am confused. What did I get wrong again? What is the difference between 250 ml/min and 250 mL per minute? I am an anesthesiologist trained in the art of close circuit anesthesia so I should be able to understand your detailed explanation. I occasionally misspeak but...

At exercise that man can burn 5-6 L/min.

For a 70 kg man, that works out to about 70-85 mL/kg/min. Not impossible, but at the upper end of human performance. Incidentally, that works out to 20-24 METs.

So.....? Your point. That increase in oxygen delivery (actually, the O2 increase isn't quite as much as the mets increase because everyone is anaerobic at that point so at least a few of the muscles are not getting all the oxygen they need for the work they are doing). Luckily, the heart isn't one of them.

Let me add one more extraneous fact. When we go anaerobic it is not because the lungs cannot take in more oxygen. Normal lungs are never the limiter. It is usually not because the heart can't pump more. A normal heart is never the limiter. We are forced to stop because the pH gets screwed up. The reason we can exercise for any length of time when we go anaerobic is because of the bicarbonate buffer system.

Oxygen carrying capacity of the blood doesn't change.

Who said it does? Why is that relevant?

If you understood oxygen delivery you would understand that in this instance increased delivery comes about mainly from increasing cardiac output. It is reasonable to assume that cardiac output increases as the mets increase. Since cardiac output increase more than the HR something else must be going on. What could it be?

If CO can only increase 4-6 times then the max mets possible would be 4-6 and we would all be striving to get to a 10 hour marathon.

This part really gets me, to the point where I think you must be trolling. Seriously, please quote some values for resting and maximal Cardiac Outputs. I still want to see where you are coming up with a 20-fold increase.

You don't understand yet do you. I don't care what the actual cardiac outputs are. All I care about are the relative mets. That is all I need to know to use the study to evaluate risk.

The met is what your body is receiving and using at rest. I believe it a safe assumption that whatever your HR is at rest it is delivering exactly 1 met.

[Yes, as I said previously, one MET equals the resting VO2. Since resting HR varies so much within and between subjects, how can you possibly use resting HR in any calculation to estimate max METs?

Because all I care about is the relative mets that each individual is at. It is unimportant what those mets represent in O2, or calories, or anything else. Normal hearts are the same and respond to stress in a similar fashion. The numbers may change between people but it is the relative changes that are important for this evaluation. And, I agree that resting HR does vary a lot between individuals. And, when unstimulated the resting HR will vary inversely with the state of aerobic fitness. Individuals with failing hearts (in congestive heart failure) have very tiny reserve and resting HR above 100 sometimes. Elite athletes (with huge reserves) have resting HR in the 30's. Most sedentary people are in the 70-80's

Give me your data and let me see how close I come.

[frankencrank]

Some people here are seriously over thinking things and have disappeared down the rabbit hole.

Once you decide you do not want to be a couch potato your whole life and start some regular exercise all your interested in how you are placed against the general population not elite athletes

If you can hit 75th percentile or better I don't think you need to worry about the state of your fitness.

How does one know where they stand. Apple was telling me I am below average when I am clearly 75th percentile or better. That is the point of my idea, giving a better assessment than what is available now.

[frankencrank]

For those that question what is going on regarding cardiac output here is a link for you.https://academic.oup.com/bjaed/article/4/6/185/314696

From this paper.

The increase in blood flow to muscles requires an increase in the cardiac output, which is in direct proportion to the increase in oxygen consumption. The cardiac output is increased by both a rise in the heart rate and the stroke volume attributable to a more complete emptying of the heart by a forcible systolic contraction. These chronotropic and inotropic effects on the heart are brought about by stimulation from the noradrenergic sympathetic nervous system. The increase in heart rate is also mediated by vagal inhibition and is sustained by autonomic sympathetic responses and carbon dioxide acting on the medulla.

The efficacy of systolic contraction is particularly important in trained athletes who can achieve significant increases in cardiac output as a consequence of hypertrophy of cardiac muscle. Table 2 shows that increased maximal cardiac output in endurance trained athletes is a function of greater stroke volume rather than an increase in maximal heart rate, which is, in fact, lower in these athletes.

Table 2
Comparison of cardiac function between athletes and non-athletes
------------------------Stroke volume (ml) -----------Heart rate (beats min−1)
At rest
Non-athlete------------------ 70---------------------------------70
Trained athlete---------------100---------------------------------50
Maximum exercise
Non-athlete-----------------110 --------------------------------190
Trained athlete---------------160--------------------------------180


Heart rate and stroke volume increase to about 90% of their maximum values during strenuous exercise and cardiovascular function is the limiting factor for oxygen delivery to the tissues. Oxygen utilization by the body can never be more than the rate at which the cardiovascular system can transport oxygen to the tissues. There is only a moderate increase in blood pressure secondary to the rise in cardiac output. This is caused by stretching of the walls of the arterioles and vasodilatation, which in combination reduce overall peripheral vascular resistance. There is a large increase in venous return as a consequence of muscular contraction, blood diversion from the viscera and vasoconstriction.

Note in the above chart that the non-athlete achieves a higher HR than the athlete. Max HR is not an indicator of aerobic fitness.

I disagree with the statement that cardiovascular function is the limiting factor. It superficially appears that way but the heart function drops off as pH changes occur due to lactate buffering in the periphery.

Let me add one more thing. The trained athletes of this study, with a resting HR of 50, are clearly not elite aerobic athletes. Most studies like this use college kids volunteers. Most will be club sport athletes.

[JaapvanE]

How does one know where they stand. Apple was telling me I am below average when I am clearly 75th percentile or better. That is the point of my idea, giving a better assessment than what is available now.

Who cares? As I said before: any metric is a guess based on half decent measurement combined with tons of assumptions. Be better than yesterday. Who cares what the rest does.

And please note: a company like Apple or Garmin really know what they are doing. They know the data far better than you do, they have AI and other tools and they have people who can write algorithms based on the data. And they are under quite some pressure to deliver new functionality. So I think that some humility is needed when you think that using two simple metrics you can detect risk of heart failure. Even high end apps like Cardiogram take a ton of data to analyze before they even suggest any risk exposure.

[frankencrank]

How does one know where they stand. Apple was telling me I am below average when I am clearly 75th percentile or better. That is the point of my idea, giving a better assessment than what is available now.

Who cares? As I said before: any metric is a guess based on half decent measurement combined with tons of assumptions. Be better than yesterday. Who cares what the rest does.

And please note: a company like Apple or Garmin really know what they are doing. They know the data far better than you do, they have AI and other tools and they have people who can write algorithms based on the data. And they are under quite some pressure to deliver new functionality. So I think that some humility is needed when you think that using two simple metrics can detect risk of heart failure. Even high end apps like Cardiogram take a ton of data to analyze before they even suggest any risk exposure.

Apple did not know me very well. My metric does a better job, at least for me. I am trying to find out if it works for others also. Not getting much help.

And, models (metrics) are not guesses. They usually are not perfect but, with refinement, can be pretty good for the question they are trying to answer. I have no clue who is figuring this stuff out for Apple. But, I can assure you being "smart" does not mean you see everything or understand everything. My guess is they have a bunch of exercise physiologists whose knowledge of cardiac physiology is limited. If they have a bunch of cardiac anesthesiologists then I take that back.

[Mike Caviston]

I am confused. What did I get wrong again?

I said that resting VO2 is 3.5 mL/kg/min, and you said I should check my data because resting VO2 is 250 mL. There is no difference but you didn’t recognize that. Otherwise why bring up 250 mL and tell me to check my data?

Let me add one more extraneous fact. When we go anaerobic...

Only one? Many of your “facts” are irrelevant or unrelated to the subject at hand. I only asked you about Cardiac Output and how resting HR is related to the MET. Concepts such as “going anaerobic” and the “anaerobic threshold” are beside the point now but I have discussed them in some detail previously. If you (or others) are interested, here are some examples:

viewtopic.php?f=3&t=10977&hilit=anaerobic+threshold

viewtopic.php?f=3&t=4401&hilit=anaerobic+threshold

viewtopic.php?f=3&t=4421&p=65689&hilit= ... old#p65689

If you understood oxygen delivery you would understand that in this instance increased delivery comes about mainly from increasing cardiac output.

I understand O2 delivery very well, which is why I am absolutely astounded that you initially insisted Cardiac Output can increase 20x above resting values, and then claim you don’t know or care what actual values are.

I don't care what the actual cardiac outputs are. All I care about are the relative mets. That is all I need to know to use the study to evaluate risk... Because all I care about is the relative mets that each individual is at. It is unimportant what those mets represent in O2, or calories, or anything else.

FYI, “relative METs” is redundant because METs are a relative value. It is very important what METs represent in O2, because METs by definition are multiples of resting VO2. If you are estimating METs based on some other value, you have to know how that other value relates to actual VO2. It is beyond me how resting HR can be the basis for an estimate. However, let’s leave that alone. I’m not your target audience, so don’t waste time (yours, mine, or others) on trying to explain it to me.

I do have one final question, if you care to answer it. What are the details of the stress test you referenced at the beginning of the thread? Was it a true max VO2 test with respiratory gas exchange, or was VO2 estimated by other means? What protocol was used? What was your final RQ?

[JaapvanE]

I have no clue who is figuring this stuff out for Apple. But, I can assure you being "smart" does not mean you see everything or understand everything. My guess is they have a bunch of exercise physiologists whose knowledge of cardiac physiology is limited. If they have a bunch of cardiac anesthesiologists then I take that back.

If you see how active this research field is, and how much is developed at companies like FirstBeat and the like, you see PhD's and part-time professors. I guess companies like Apple and Google/FitBit have a similar team buildup. The relation with medical universities is extremely close in that area as the development of sensors and algorithms are so intertwined and stuff is pretty close to the field. This is bleeding edge stuff that is heading for medical approval (where the science has to back up your numbers), not an intern that codes something in the night that might make it to the product.

[gvcormac]

JaapvanE:

I'd be very interested to learn more about the history of C2 and the open project you're talking about. I have read the original C2 patent and I think it is quite clever. I don't agree that it makes wild assumptions in calculating power to the flywheel. It needs to know the angular moment and velocity of the flywheel, which are, respectively, constant and measured quite readily. It then needs to numerically calculate the derivative (acceleration) and an integral (power to energy).

As the paper you mentioned notes, if the acceleration is very jerky, these numerical calculations can be off a bit, but only by a couple of percent.

I find it ironic that although it is called an ergometer, it doesn't report ergs or joules or newton-meters or any other objective measure of work done. Of course you can multiply duration by average watts to get joules. They do report Calories which is another measure of work but -- correct me if I'm wrong -- this is not calories at the flywheel (1 cal = 4.18 joule) but some wild-assed estimate of metabolic calories.

I also agree that the distance estimates are artificial. But they -- like the Calorie estimates -- are consistent.

G

P.S. The bike strain gauge ergs have, I think, an even trickier job: double numerical integration, to get from force to angular velocity to distance.

[frankencrank]

I am confused. What did I get wrong again?

I said that resting VO2 is 3.5 mL/kg/min, and you said I should check my data because resting VO2 is 250 mL. There is no difference but you didn’t recognize that. Otherwise why bring up 250 mL and tell me to check my data?

Let me add one more extraneous fact. When we go anaerobic...

Only one? Many of your “facts” are irrelevant or unrelated to the subject at hand. I only asked you about Cardiac Output and how resting HR is related to the MET. Concepts such as “going anaerobic” and the “anaerobic threshold” are beside the point now but I have discussed them in some detail previously. If you (or others) are interested, here are some examples:

viewtopic.php?f=3&t=10977&hilit=anaerobic+threshold

viewtopic.php?f=3&t=4401&hilit=anaerobic+threshold

viewtopic.php?f=3&t=4421&p=65689&hilit= ... old#p65689

If you understood oxygen delivery you would understand that in this instance increased delivery comes about mainly from increasing cardiac output.

I understand O2 delivery very well, which is why I am absolutely astounded that you initially insisted Cardiac Output can increase 20x above resting values, and then claim you don’t know or care what actual values are.

I don't believe you understand cardiorespiratory physiology well. You may have a basic knowledge but, very well? I don't think so. Where did you gain this knowledge?

I don't care what the actual cardiac outputs are. All I care about are the relative mets. That is all I need to know to use the study to evaluate risk... Because all I care about is the relative mets that each individual is at. It is unimportant what those mets represent in O2, or calories, or anything else.

FYI, “relative METs” is redundant because METs are a relative value. It is very important what METs represent in O2, because METs by definition are multiples of resting VO2. If you are estimating METs based on some other value, you have to know how that other value relates to actual VO2. It is beyond me how resting HR can be the basis for an estimate. However, let’s leave that alone. I’m not your target audience, so don’t waste time (yours, mine, or others) on trying to explain it to me.

Are you trolling here? The mets at rest and at exercise are relative to each other. Of course I am estimating mets based upon some other value (the change in the HR) because one cannot measure them directly even in the lab (where they can be estimated based upon oxygen consumption).

I do have one final question, if you care to answer it. What are the details of the stress test you referenced at the beginning of the thread? Was it a true max VO2 test with respiratory gas exchange, or was VO2 estimated by other means? What protocol was used? What was your final RQ?

A treadmill ramp test, almost to exhaustion (I could have gone a little longer but the technician stopped it - I had stopped him from ending it earlier as I wasn't near exhaustion). The purpose was to do ultrasound to check heart function when stressed. I passed. Mets would have been calculated based upon some formula using my weight, slope, and speed I am sure. I didn't double check what the doctor told me.

So, tell me again how you became so learned in cardiac physiology. I am trained as an anesthesiologist and taught residents in the UC San Francisco system.

[frankencrank]

I have no clue who is figuring this stuff out for Apple. But, I can assure you being "smart" does not mean you see everything or understand everything. My guess is they have a bunch of exercise physiologists whose knowledge of cardiac physiology is limited. If they have a bunch of cardiac anesthesiologists then I take that back.

If you see how active this research field is, and how much is developed at companies like FirstBeat and the like, you see PhD's and part-time professors. I guess companies like Apple and Google/FitBit have a similar team buildup. The relation with medical universities is extremely close in that area as the development of sensors and algorithms are so intertwined and stuff is pretty close to the field. This is bleeding edge stuff that is heading for medical approval (where the science has to back up your numbers), not an intern that codes something in the night that might make it to the product.

You are guessing as to their team. All I can say is they sure got me wrong. I tried to open a dialogue with Apple about the problem and was ignored of course. That is why I started to look at the technology to see if I could figure out the problem and see if it could actually give me a more correct assessment. I am trying to get some data to try to validate the approach I cam up with.

Surely someone has some data they would share to help me out?

[frankencrank]

JaapvanE:

I'd be very interested to learn more about the history of C2 and the open project you're talking about. I have read the original C2 patent and I think it is quite clever. I don't agree that it makes wild assumptions in calculating power to the flywheel. It needs to know the angular moment and velocity of the flywheel, which are, respectively, constant and measured quite readily. It then needs to numerically calculate the derivative (acceleration) and an integral (power to energy).

As the paper you mentioned notes, if the acceleration is very jerky, these numerical calculations can be off a bit, but only by a couple of percent.

I find it ironic that although it is called an ergometer, it doesn't report ergs or joules or newton-meters or any other objective measure of work done. Of course you can multiply duration by average watts to get joules. They do report Calories which is another measure of work but -- correct me if I'm wrong -- this is not calories at the flywheel (1 cal = 4.18 joule) but some wild-assed estimate of metabolic calories.

I also agree that the distance estimates are artificial. But they -- like the Calorie estimates -- are consistent.

G

P.S. The bike strain gauge ergs have, I think, an even trickier job: double numerical integration, to get from force to angular velocity to distance.

I think you are in the wrong thread.

What makes C2 not a true ergometer is they don't account for the work done overcoming the shock cord. It would be very easy to do but they chose not to. What makes it valuable as a "scientific" training tool is output is repeatable and self calibrating.