Looking for fitness information

[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 make one clarification for those who are still here and interested in the physiology.

Basal oxygen requirement varies with weight but not linearly. In anesthesia the basal oxygen requirement for closed circuit anesthesia can be estimated quite well and it varies with the mass to the 3/4 power. This is true for all mammals. It is because most of that requirement is to maintain the temperature of the organism and the temperature loss varies with the surface area, which does not follow the mass linearly. 3.5ml/kg/min is what is expected for a 70 Kg man. That formula does not hold for everyone. As an example. A 100 kg man would be expected to have a basal uptake of about 327 ml/min. This is 3.27 ml/kg/min, not 3.5. A 50 kg woman would be expected to have a basal need of about 194 ml/min or 3.88 ml/kg/min.

3.5ml/kg/min is only correct for one weight. It gets close when applied to other weights if they are not too far from 70 kg but it is not a correct formula for predicting basal oxygen uptake.

[Mike Caviston]

I don't believe you understand cardiorespiratory physiology well.

Based on the comments you keep making, I understand it better than you. You said:

First, I am not trying to estimate VO2max. Rather, I am trying to estimate METS capacity as that is the basis of the risk assessment. They are related but different. Here is the thought. Cardiac output can increase about 20 times. HR can only increase about 4 times.

VO2 max is the same as METs capacity since METs are calculated from VO2. Saying your capacity based on VO2 is different from your capacity based on METs is like saying your weight expressed in kilograms is different from your weight expressed in pounds. Then, saying cardiac output can increase 20 times is so far outside reality it’s as if you are insisting the human heart is the size of a giant pumpkin. Somebody trained in cardiology really should know. I pointed out that resting CO is about 5 L/min and during max exercise it will reach 20-30 L/min depending on fitness/training. You next insisted that if CO only increased 4-6 times it would be difficult to run a marathon in under 10 hours. Then, to validate your authority, you quoted some information from an article, including a table comparing resting and max cardiac outputs of non-athletes and trained athletes. The table shows resting CO is about 5 L/min for both non-athletes and athletes (with different resting HR and SV), max CO is about 21 L/min for non-athletes (a 4-fold increase), and max CO id about 29 L/min for trained athletes (a 6-fold increase). Which is exactly what I said so thanks for validating my knowledge of physiology. But it doesn’t support your claim that CO can increase 20-fold, so you say, well, these trained athletes aren’t really trained athletes, they’re just college kids. So “real” trained athletes can increase CO 20-fold? I’d love to see the research supporting that. If you google Miguel Indurain, the Internet insists his cardiac output was 50 L/min but doesn’t offer any proof. Anyway, however well I understand physiology, at least in this case I clearly understand it better than you.

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.

Thanks for sharing. In your initial post, you were upset that the Apple Watch didn’t rate your exercise capacity as highly as your stress test did. But your stress test isn’t the gold standard either because it was submaximal and didn’t directly measure oxygen uptake. Your heart functions well when stressed so well done and I hope you enjoy good health for a long time, but the test wasn’t intended to determine your exercise capacity. Your exercise capacity is clearly better than the Apple Watch value, but I’m sure you didn’t need a stress test to tell you that. (I wouldn’t care what a watch tells me about exercise capacity because my actual exercise tells me about my exercise capacity.) I know you have explained already, but perhaps you can clarify exactly what you are looking for, since there is a difference between what a watch might show you regarding your exercise capacity (a performance metric) vs what it might show you regarding your response to a stress test (a health metric). Apologies if you think you’ve already made this clear, and as I said before don’t waste time purely on my account, but I don’t think I’m the only one confused on this point.

[frankencrank]

I don't believe you understand cardiorespiratory physiology well.

Based on the comments you keep making, I understand it better than you. You said:

First, I am not trying to estimate VO2max. Rather, I am trying to estimate METS capacity as that is the basis of the risk assessment. They are related but different. Here is the thought. Cardiac output can increase about 20 times. HR can only increase about 4 times.

VO2 max is the same as METs capacity since METs are calculated from VO2. Saying your capacity based on VO2 is different from your capacity based on METs is like saying your weight expressed in kilograms is different from your weight expressed in pounds. Then, saying cardiac output can increase 20 times is so far outside reality it’s as if you are insisting the human heart is the size of a giant pumpkin. Somebody trained in cardiology really should know. I pointed out that resting CO is about 5 L/min and during max exercise it will reach 20-30 L/min depending on fitness/training. You next insisted that if CO only increased 4-6 times it would be difficult to run a marathon in under 10 hours. Then, to validate your authority, you quoted some information from an article, including a table comparing resting and max cardiac outputs of non-athletes and trained athletes. The table shows resting CO is about 5 L/min for both non-athletes and athletes (with different resting HR and SV), max CO is about 21 L/min for non-athletes (a 4-fold increase), and max CO id about 29 L/min for trained athletes (a 6-fold increase). Which is exactly what I said so thanks for validating my knowledge of physiology. But it doesn’t support your claim that CO can increase 20-fold, so you say, well, these trained athletes aren’t really trained athletes, they’re just college kids. So “real” trained athletes can increase CO 20-fold? I’d love to see the research supporting that. If you google Miguel Indurain, the Internet insists his cardiac output was 50 L/min but doesn’t offer any proof. Anyway, however well I understand physiology, at least in this case I clearly understand it better than you.

I will accept I made an error when I said CO increased 20 times when I meant Oxygen delivery increased 20 times. It is the interweb and my editor is on vacation. Your problem is your intent is to belittle me when all I asked for was for real world test results that I could use to validate an idea I have. An idea you clearly do not understand.

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.

Thanks for sharing. In your initial post, you were upset that the Apple Watch didn’t rate your exercise capacity as highly as your stress test did. But your stress test isn’t the gold standard either because it was submaximal and didn’t directly measure oxygen uptake. Your heart functions well when stressed so well done and I hope you enjoy good health for a long time, but the test wasn’t intended to determine your exercise capacity. Your exercise capacity is clearly better than the Apple Watch value, but I’m sure you didn’t need a stress test to tell you that. (I wouldn’t care what a watch tells me about exercise capacity because my actual exercise tells me about my exercise capacity.) I know you have explained already, but perhaps you can clarify exactly what you are looking for, since there is a difference between what a watch might show you regarding your exercise capacity (a performance metric) vs what it might show you regarding your response to a stress test (a health metric). Apologies if you think you’ve already made this clear, and as I said before don’t waste time purely on my account, but I don’t think I’m the only one confused on this point.

I guess you are presuming my cardiologist doesn't know what he is doing when he reported to my the mets I achieved on my stress test. Whether you consider it sub maximal or not makes no difference. To me, it was, essentially a max stress test. I managed to reach a HR above 165 as I remember, not bad for a 78 yo. If you think it was sub maximal then my result should be even higher.

Just as I did in Cardia rehab I take advantage of the environment to push myself when there are trained people there to take care of any problems that might occur. Since there were no problems I now feel reasonably comfortable pushing myself when alone.

While one can presume ones exercise capacity is above normal the value of an EST is it validates the thought and, in some ways, quantitates it.

I am comfortable Apple Watch is assessing me wrongly. I am curious as to why and how can it be corrected. If you don't care, go on with your life. Ignorance is bliss.

[gvcormac]

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.

I didn't know there were right and wrong threads. I was responding to a comment in this thread. I'd be happy enough to see the discussion in another.

The C2 PM(x) measures work delivered to the flywheel. It does not measure all mechanical work done by the body. I don't see why that makes it "not a true ergometer."

The C2 apparently doesn't account for losses in the bungee cord, or losses in the chain or the seat/rail, or recovery. In other words, it measures work delivered to the flywheel. The cord/chain/rail losses pale compared to recovery.

I suggest "reliable" is a better word than "<quote>scientific<unquote>"

[JaapvanE]

I'd be very interested to learn more about the history of C2

see https://www.youtube.com/watch?v=sFkfcxZS58w, I really love their down to earth approach.

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.

Good idea, I picked up these old patents, they nicely describe how we do things as well. I never saw them, but they are a work of beauty. I think that Prof. van Holst and Anu Dudhia deserve all the credits: they have written down the real physics and are the basis for every open source rowing monitor out there (see http://eodg.atm.ox.ac.uk/user/dudhia/ro ... meter.html).

We indeed initially started with a numerical approximation as the formula's of Anu Dudhia suggest that. When it comes down to implementation, you see that time between impulses is indeed a bit noisy. This makes Angular Velocity a bit more noisy and Angular Acceleration even much more noisy. So I implemented a different engine based on linear regression to calculate the slopes, which delivers much more stable results and is more robust to noise and outliers.

The essence of the patent describes the backbone of a stable calculation quite well: you calculate the drag in the recovery phase, and then use that to convert angular displacement into linear displacement, with the Peter's magic number 2.8 and the drag between them. As the patent suggests, From there on, all displayed metrics can be calculated from linear displacement. This delivers quite stable results, and that is why the new version of Open Rowing Minotr is within 0.03% of C2's results.

C2's approach makes some critical shortcuts, the most important being that they don't take in account the angular velocity changes across strokes. Both our validation and the research of the university of Ulm confirm this (see https://www.researchgate.net/publicatio ... d_Test_Rig). Their conclusion is that when the rower isn't using a real steady state row, the power metrics are off considerably. I understand why they took the shortcut (the alternative is a more accurate but much more vulnerable to small errors), we made the same shortcuts, but that is the typicall trade-off you have to make when you have limited resources and still want to display things real-time.

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.

It is one of the many shortcuts you need to make to get to some meaningful number. From the description of Anu Dudhia according to a named source within Concept2:

The 300 kC/hour has always been our best approximation for keeping alive and awake and going through the rowing motion at a reasonable stroke rate on an erg with the flywheel removed. This was arrived at from internal experiments and observations, data from Fritz Hagerman and studies done at Ball State.

It isn't a wild assumption per se, but it is an population average applied to a single individual. So by definition, it won't fit anyone well. Here a couple of additional parameters (rower weight, SPM, etc.) might make it a better model, but this simplicity makes the calculation robust and simple. And as long as nobody makes life or death decission based on these metrics, why should one care.

And that is the fundamental issue with most models: when you find out that 2 metrics account for 95% of your outcome, it makes sense to remove all other metrics. This is fine when the remaining 5% at best is dissapointed, but for some applications you can't take that risk (like the applications Frank proposed here).

[Mike Caviston]

I will accept I made an error when I said CO increased 20 times when I meant Oxygen delivery increased 20 times. It is the interweb and my editor is on vacation. Your problem is your intent is to belittle me

Initially I simply asked if you really meant CO since your values were so extreme. You doubled and then tripled down on CO, so don’t throw your “editor” under the bus. My “problem” is that you belittle anyone else’s understanding of physiology because they don’t have your background.

I guess you are presuming my cardiologist doesn't know what he is doing when he reported to my the mets I achieved on my stress test.

I didn’t presume anything because you provided the details. Your cardiologist knew what he was doing when he told you your heart responded well under stress (the purpose of the test) but he only estimated your METs (not the purpose of the test) and you don’t know the details of how the estimate was made. So you’re in good shape, and are reasonably confident you can push yourself on your own. Mission accomplished.

I am comfortable Apple Watch is assessing me wrongly. I am curious as to why and how can it be corrected. If you don't care, go on with your life. Ignorance is bliss.

Good. You have come to terms with it after being “really bothered” two days ago. I might enjoy the challenge of solving a physiological puzzle under different circumstances, but clearly this isn’t the time or place. This is my last response in this thread. Good luck with your quest.

[gvcormac]

I'd be very interested to learn more about the history of C2

see https://www.youtube.com/watch?v=sFkfcxZS58w, I really love their down to earth approach.

I have read the original C2 patent and I think it is quite clever.

[ . . . ]

And that is the fundamental issue with most models: when you find out that 2 metrics account for 95% of your outcome, it makes sense to remove all other metrics. This is fine when the remaining 5% at best is dissapointed, but for some applications you can't take that risk (like the applications Frank proposed here).

Thanks for the info. That's why I'd rather have an objective measure -- watts/joules at the flywheel -- than a bunch of baked in guesses. That said, I communicate in the fake time/distance numbers because that is what everyboy else does. I suppose the fake calorie numbers are OK so long as the arbitrary constants are the same for everybody. My treadmill and elliptical use some body weight factor. At least (I think) your C2 calorie is the same as my C2 calorie. Definitely your C2 distance is the same as mine (modulo the approximations we have discussed).

In another thread, perhaps I'll rail on about HR zones, METs, etc.

[JaapvanE]

Thanks for the info. That's why I'd rather have an objective measure -- watts/joules at the flywheel -- than a bunch of baked in guesses. That said, I communicate in the fake time/distance numbers because that is what everyboy else does. I suppose the fake calorie numbers are OK so long as the arbitrary constants are the same for everybody. My treadmill and elliptical use some body weight factor. At least (I think) your C2 calorie is the same as my C2 calorie. Definitely your C2 distance is the same as mine (modulo the approximations we have discussed).

In another thread, perhaps I'll rail on about HR zones, METs, etc.

My calories probably won't be yours in real life: a key element in the calculation underpinning 300 calories should be the persons weight. But then again: most people don't make a big deal out of it.

Regarding the distance: it should be OK across rowers, as the assumptions in that calculation are extremely limited (just the magic number 2.8), although in theory a term is missing to compensate for varying flywheel velocities across strokes. That "rewards" people with good steady state technique and little stroke-to-stroke variation disproportionally. But as assumptions go, I kind of like that one to be honest as it highlights good technique, as a training tool should.

[gvcormac]

My calories probably won't be yours in real life: a key element in the calculation underpinning 300 calories should be the persons weight. But then again: most people don't make a big deal out of it.

If we're talking about work applied to the flywheel, my calorie = your calorie = 4.2 joules = 4.2 newton-metres = 0.004 BTU.

By convention, Americans measure food energy in Calories (i.e. Kcal). I'm not interested in how much food energy I'm consuming. I'm interested in how much work I'm doing. Clearly food energy will be something larger than that, because neither my body nor the equipment is 100% efficient. How much larger is anybody's guess, and I don't want that guess built into my exercise equipment.

[Ombrax]

If we're talking about work applied to the flywheel, my calorie = your calorie = 4.2 joules = 4.2 newton-metres = 0.004 BTU.

By convention, Americans measure food energy in Calories (i.e. Kcal). I'm not interested in how much food energy I'm consuming. I'm interested in how much work I'm doing. Clearly food energy will be something larger than that, because neither my body nor the equipment is 100% efficient. How much larger is anybody's guess, and I don't want that guess built into my exercise equipment.

1) When the PM displays Watts I believe that's power input to the flywheel.

2) When the PM displays Calories I believe that's the "guesstimate" of what the person rowing expended (in terms of calories food required to do the work performed on the rower)

The following is from the C2 web site:

A Word About Calories:

Due to the differences in body weight and efficiency, calories on the PM are only an approximation of calories burned by the person rowing. The formula used in the PM2 is as follows:

Calories = (4x ave. watts/1.1639) + 300 cal/hour x time rowed (in hours).

This formula assumes a person of 175 pounds (80 kg.) and a base rate of 300 cal/hour to move your body through the rowing motion at 30 strokes/minute.

The method used to calculate calories could obviously be improved, but as you say, who really cares - most likely not "serious" rowers, just the casual folks who hop on the machine at the gym.

[Dangerscouse]

The method used to calculate calories could obviously be improved, but as you say, who really cares - most likely not "serious" rowers, just the casual folks who hop on the machine at the gym.

In my personal view, I couldn't be less interested in calories on the monitor. It's never been something that I look at.

[gvcormac]

The method used to calculate calories could obviously be improved, but as you say, who really cares - most likely not "serious" rowers, just the casual folks who hop on the machine at the gym.

In my personal view, I couldn't be less interested in calories on the monitor. It's never been something that I look at.

But watts and watt-seconds (joules) are of interest, right? 4.2 joules = 1 calorie. Both are formally defined measures the same thing: work or energy. Like you, I don't care about how much food energy is burned; if I did I would try to measure it more accurately.

I care about the work done in a workout. The current PM is adequate for calculating overall work: average watts times time in seconds gives work in joules. Divide by 4.2 to get work in calories. I just wish it would do one of these instead of the [food] Calorie estimate.

[Carl Watts]

I have never looked at the Calories in 12 years of rowing, total waste of time your simply not interested in it. Probably stuck in there for those in a gym environment. Just another thing that would get dropped and replaced with far more useful information if they made a second version of the PM5 firmware for serious rowers.

[JaapvanE]

But watts and watt-seconds (joules) are of interest, right? 4.2 joules = 1 calorie. Both are formally defined measures the same thing: work or energy. Like you, I don't care about how much food energy is burned; if I did I would try to measure it more accurately.

I care about the work done in a workout. The current PM is adequate for calculating overall work: average watts times time in seconds gives work in joules. Divide by 4.2 to get work in calories. I just wish it would do one of these instead of the [food] Calorie estimate.

That is a fair point to be honest. I'll think I might change that for Open Rowing Monitor. Or make sure we have a better estimate for calories burnt rowing.....

[JaapvanE]

I have never looked at the Calories in 12 years of rowing, total waste of time your simply not interested in it. Probably stuck in there for those in a gym environment. Just another thing that would get dropped and replaced with far more useful information if they made a second version of the PM5 firmware for serious rowers.

I agree with you on the uselessness of the Calorie count, but what additional metric would you display Carl?