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It turns out that bone loss in cyclists is because of sweating

Old 04-18-20, 07:48 PM
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It turns out that bone loss in cyclists is because of sweating

Back in November I did some sweat loss calculations and concluded that bone loss during cycling wasn't because of losing calcium in sweat. Turns out I was wrong about that in this post: 🤔 Nootropics: "Smart Drugs"
and I take it back. Bone loss is due to sweating. It has little or nothing to do with cycling being non-weight bearing, it's just the sweating. There's a good paper on it here: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3145631/

The good news in that paper and other similar studies is that taking calcium about 2 hours before riding attenuates the bone loss. One study used 1000mg calcium citrate and 1000mg of vitamin D3.

There's also a paper showing that supplementing 1000mg/day calcium also increases cycling performance: https://pdfs.semanticscholar.org/9d3...2565818304.pdf

It's recommended that if one supplements with calcium to also take magnesium in a 2:1 ratio, but not at the same time, though that wasn't done in these studies. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4717874/
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Old 04-18-20, 09:01 PM
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That’s interesting to say the least. Great info.

I have read that strength training is excellent for maintaining and even building bone.


“Numerous studies have shown that strength training can play a role in slowing bone loss, and several show it can even build bone. This is tremendously useful to help offset age-related declines in bone mass. Activities that put stress on bones can nudge bone-forming cells into action. That stress comes from the tugging and pushing on bone that occur during strength training (as well as weight-bearing aerobic exercises like walking or running). The result is stronger, denser bones.

And strength training, in particular, has bone benefits beyond those offered by aerobic weight-bearing exercise. It targets bones of the hips, spine, and wrists, which are the sites most likely to fracture. What's more, resistance workouts — particularly those that include moves emphasizing power and balance — enhance strength and stability. That can boost confidence, encourage you to stay active, and reduce fractures another way — by cutting down on falls.”

https://www.health.harvard.edu/stayi...e-than-muscles
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Old 04-19-20, 11:01 AM
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I started strength training in the gym about 2 years after I started cycling training, so uh . . .23 years ago. I strength trained for about 8 months/year + backpacked. I did heavy squats and similar leg and pelvis work, got lots stronger, rode well, but it apparently didn't help with the bone loss. I've mostly done endurance cycling, so long rides. My rheumaticist says it was because of lack of calcium. I didn't supplement because of the studies showing it didn't help sedentary folks and increased risk of heart disease, and I drank no milk and in general, didn't consume that much dairy. 1000mg calcium is a quart of milk.

I started a thread encouraging strength training in cyclists: Introduction to strength training for the endurance athlete

I started the 1000mg calcium + magnesium the day I started this thread. Ask me in 5 years if it worked.
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Old 04-19-20, 11:31 AM
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I do strength training also because it is a good alternative. Gives you diversity, once a week in summer, twice a week in winter. Not to mention it has amazing health benefits. I do lower body work along with deadlifts, and then some core and flexibility work. I think deadlifts have helped me stay in good position on the bike and have a strong core and lower back. Plus, similarly to raising your wattage / FTP, it is fun to see your lifts going up over time. I started at 60kg deadlift and before corona hit I just hit 110kg.
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Old 04-19-20, 03:25 PM
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My docs have me on large doses of Vitamin D, calcium, etc., to help with bone density loss due to osteopenia related to failure of my thyroid/parathyroid. No indication in lab tests it's helping. I don't notice any difference in my workouts.

I take the stuff but I'm skeptical about whether it's doing any good. Once the endocrine system messes up we're pretty much slapping bandaids on a leaking dam.
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Old 04-19-20, 04:22 PM
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What about sweating during weight-bearing activities such as weightlifting, hiking, running...would sweating during those activities have a negative effect on bone calcium and density ??
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Old 04-19-20, 06:55 PM
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Originally Posted by Carbonfiberboy View Post
I started strength training in the gym about 2 years after I started cycling training, so uh . . .23 years ago. I strength trained for about 8 months/year + backpacked. I did heavy squats and similar leg and pelvis work, got lots stronger, rode well, but it apparently didn't help with the bone loss. I've mostly done endurance cycling, so long rides. My rheumaticist says it was because of lack of calcium. I didn't supplement because of the studies showing it didn't help sedentary folks and increased risk of heart disease, and I drank no milk and in general, didn't consume that much dairy. 1000mg calcium is a quart of milk.

I started a thread encouraging strength training in cyclists: Introduction to strength training for the endurance athlete

I started the 1000mg calcium + magnesium the day I started this thread. Ask me in 5 years if it worked.
Yes, I’ve heard the same, that calcium supplements don’t “take” as far as bone loss.

And if the calcium loss is dermal, if that’s the right word, I hope it can be replenished via supplements, that’s a very interesting study.

Riding for hours a day seems to place the body in an imbalance as far as maintaining bone density. It would seem that one would either need to cycle less and/or be sure to pair their fitness routine with a good balance of strength training plus add calcium supplements.

I found this...
“They also may have been sweating out more calcium than they were taking in, leaving their bones even more vulnerable. The researchers noted that losing large amounts of calcium during exercise can trigger hormonal activity associated with bone loss. Though they didn’t ask about calcium timing, some research suggests that eating a calcium-rich meal 90 minutes before intensive exercise can help lessen that bone-depleting hormonal activity.

Finally, it bears mentioning that this study was conducted in Norway, a country that has one of the highest rates of osteoporosis and bone fracture rates in the world, possibly due to insufficient sun exposure, which helps the body create bone-building vitamin D.

Bottom line: To keep your bones strong, pay as much attention to your strength-training routine—yes, that means making the time to fit it into your routine year-round—as you do your riding. Check out these 10 essential strength moves for cyclists, and how you can implement them into your program.“



https://www.bicycling.com/health-nut...ngth-training/
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Old 04-19-20, 08:01 PM
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Originally Posted by wolfchild View Post
What about sweating during weight-bearing activities such as weightlifting, hiking, running...would sweating during those activities have a negative effect on bone calcium and density ??
One doesn't sweat enough in the gym, and not for enough hours. Just my guess, but riders who experience accelerated bone probably ride a fair bit, say 10 hours a week or so. It's dermal calcium loss/hour X hours. Hiking - I don't know. No data. Running - there are studies which show no bone loss and studies which do show it. My guess is that it's intensity and time. IOW ultra runners are at risk : https://www.irunfar.com/2019/06/bone...e-runners.html

That's what I meant about it not being the lack of weight bearing in cycling, just the sweating. Ultra running is definitely weight bearing. If you sweat out calcium faster than it can be replaced, you got a problem. That's seems to be the message.

The usual rec for cycling water consumption is 1 bottle/hour, so that much sweat loss. I see guys in the gym with huge water bottles, and I do see some really hard workers sweating, but not for very long. Most gym rats don't seem to sweat at all, you know the guys who lift heavy and wait 5 minutes or so between sets.
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Old 04-19-20, 08:12 PM
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Originally Posted by CyclingBK View Post
Yes, I’ve heard the same, that calcium supplements don’t “take” as far as bone loss.

And if the calcium loss is dermal, if that’s the right word, I hope it can be replenished via supplements, that’s a very interesting study.

Riding for hours a day seems to place the body in an imbalance as far as maintaining bone density. It would seem that one would either need to cycle less and/or be sure to pair their fitness routine with a good balance of strength training plus add calcium supplements.

I found this...
“They also may have been sweating out more calcium than they were taking in, leaving their bones even more vulnerable. The researchers noted that losing large amounts of calcium during exercise can trigger hormonal activity associated with bone loss. Though they didn’t ask about calcium timing, some research suggests that eating a calcium-rich meal 90 minutes before intensive exercise can help lessen that bone-depleting hormonal activity.

Finally, it bears mentioning that this study was conducted in Norway, a country that has one of the highest rates of osteoporosis and bone fracture rates in the world, possibly due to insufficient sun exposure, which helps the body create bone-building vitamin D.

Bottom line: To keep your bones strong, pay as much attention to your strength-training routine—yes, that means making the time to fit it into your routine year-round—as you do your riding. Check out these 10 essential strength moves for cyclists, and how you can implement them into your program.“



https://www.bicycling.com/health-nut...ngth-training/
What study conducted in Norway? I didn't post a Norwegian study.

From the NCBI study I posted:
One potential mechanism is increased bone resorption due to an exercise-induced increase in parathyroid hormone (PTH), possibly triggered by dermal calcium loss. The purpose of this investigation was to determine whether calcium supplementation either before or during exercise attenuates exercise-induced increases in PTH and C-terminal telopeptide of type I collagen (CTX; a marker of bone resorption).
The study result was that they found that it did.
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Old 04-19-20, 08:13 PM
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Originally Posted by Carbonfiberboy View Post
One doesn't sweat enough in the gym, and not for enough hours. Just my guess, but riders who experience accelerated bone probably ride a fair bit, say 10 hours a week or so. It's dermal calcium loss/hour X hours. Hiking - I don't know. No data. Running - there are studies which show no bone loss and studies which do show it. My guess is that it's intensity and time. IOW ultra runners are at risk : https://www.irunfar.com/2019/06/bone...e-runners.html

That's what I meant about it not being the lack of weight bearing in cycling, just the sweating. Ultra running is definitely weight bearing. If you sweat out calcium faster than it can be replaced, you got a problem. That's seems to be the message.

The usual rec for cycling water consumption is 1 bottle/hour, so that much sweat loss. I see guys in the gym with huge water bottles, and I do see some really hard workers sweating, but not for very long. Most gym rats don't seem to sweat at all, you know the guys who lift heavy and wait 5 minutes or so between sets.
just to give an idea of how much sweating you can do riding...i live in reno and went mountain biking in the BLM that i can see out my back window, no trees, dead of summer, (with twice as much climbing as descending ). this was back when i was weighing myself before or after every ride, i had often wondered how much sweating i was doing so one time before i dressed up i weighed myself then went out riding. i consumed a small amount of food and about 32 oz of water. when i returned i stripped down and weighed again. i came in 4.5 lbs lighter. that's about 1/2 gallon of sweat. i never underestimate how much sweating i do while riding now.
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Old 04-19-20, 08:15 PM
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Originally Posted by Carbonfiberboy View Post
What study conducted in Norway? I didn't post a Norwegian study.

From the NCBI study I posted: The study result was that they found that it did.

Cool, yes, I said, “I found this” right before I posted that quote/link. I did not say you posted a Norwegian study ; )

Thanks again for posting this info.
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Old 04-19-20, 08:32 PM
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Originally Posted by Carbonfiberboy View Post
Back in November I did some sweat loss calculations and concluded that bone loss during cycling wasn't because of losing calcium in sweat. Turns out I was wrong about that in this post: 🤔 Nootropics: "Smart Drugs"
and I take it back. Bone loss is due to sweating. It has little or nothing to do with cycling being non-weight bearing, it's just the sweating. There's a good paper on it here: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3145631/

The good news in that paper and other similar studies is that taking calcium about 2 hours before riding attenuates the bone loss. One study used 1000mg calcium citrate and 1000mg of vitamin D3.

There's also a paper showing that supplementing 1000mg/day calcium also increases cycling performance: https://pdfs.semanticscholar.org/9d3...2565818304.pdf

It's recommended that if one supplements with calcium to also take magnesium in a 2:1 ratio, but not at the same time, though that wasn't done in these studies. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4717874/
i think you need to be careful about making the claim that calcium supplements counter bone loss. in the first link even in their argument for the research they admit that this is only a hypothesis. This same article states in their results that calcium supplementation prior to, or during, does not improve cycling performance, in contrast to the claim in the second link you pointed out. i read only the first link. i can read it in a half hour but i think it would take a couple to fully understand it all, much goes over my head (dammit jim, i'm an engineer, not a doctor). the second llink i began to read but at over 300 pages i quickly gave up.

i suspect that the researchers are on to something though. maybe if i remember, i'll take a tums before every ride.
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Old 04-19-20, 10:38 PM
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Originally Posted by spelger View Post
i think you need to be careful about making the claim that calcium supplements counter bone loss. in the first link even in their argument for the research they admit that this is only a hypothesis. This same article states in their results that calcium supplementation prior to, or during, does not improve cycling performance, in contrast to the claim in the second link you pointed out. i read only the first link. i can read it in a half hour but i think it would take a couple to fully understand it all, much goes over my head (dammit jim, i'm an engineer, not a doctor). the second llink i began to read but at over 300 pages i quickly gave up.

i suspect that the researchers are on to something though. maybe if i remember, i'll take a tums before every ride.
This sort of thing takes a very long time to figure out. We should know more in 5-10 years. In the meantime, like you say, doesn't hurt to be proactive. Well, we don't think it does.
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Old 04-20-20, 07:09 PM
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Too much calcium leads to kidney stones, is that right? I've heard you don't want those if you don't like pain. So how do you get just the right amount?
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Old 04-20-20, 08:38 PM
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Originally Posted by Seattle Forrest View Post
Too much calcium leads to kidney stones, is that right? I've heard you don't want those if you don't like pain. So how do you get just the right amount?
Actually, too little calcium is a greater danger w/r to kidney stones.

Information:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4708574/
https://www.health.harvard.edu/blog/...s-201310046721
https://www.healthline.com/health/ki...tones#takeaway
https://www.webmd.com/kidney-stones/...isk-in-study#1

The idea in the studies I read is that you take 1000mg of calcium a couple hours before riding, if you are going to be doing a good bit of sweating. That calcium could therefore be taken with a pre-ride meal, though my guess is that it wouldn't really matter. I don't think that's at all excessive and might actually prevent stones.

An interesting question is: during a long ride, say a 400k lasting 15-24 hours, how often would one repeat a dosage if at all, and if so, how much? Endurolytes, which I take 1/hr. on long rides, contain 50mg of calcium. My WAG is that should be about right.
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Old 04-20-20, 10:48 PM
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New Garmins attempt to guess how much sweat you lost. Not very accurate in my experience. If you could know that (weighing yourself before and after) it might help give an idea of dose.

I keep buying milk, but I don't use much of it. I'll have to give this some thought.

Thanks Carbonfiberboy .
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Old 04-21-20, 06:05 AM
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Calcium was also the only thing I found that would help reduce/prevent cramps (when I was undertrained...adequate training was always best to alleviate cramps).
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Old 04-21-20, 08:13 AM
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Originally Posted by Seattle Forrest View Post
New Garmins attempt to guess how much sweat you lost. Not very accurate in my experience. If you could know that (weighing yourself before and after) it might help give an idea of dose.

I keep buying milk, but I don't use much of it. I'll have to give this some thought.

Thanks Carbonfiberboy .
For medical dosages (which this really is), I always go by the studies. A rando buddy of mine, 6'7", would drink a quart of chocolate milk at controls. Might be a good pre-ride meal if one can tolerate it, certainly better than a pill. He'd say "I'm a quart low."
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Old 04-25-20, 08:26 AM
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I'm pretty sure that living too long contributes to bone loss as well. I was one of the subjects involved in a research study of Masters athletes that compared outcomes of runners versus cyclists. (not sure how they considered swimmers)

At the time, there was considerable attention given to various hormones involved in bone health or strength. There was also great interest in "impact jumping" or hopping.

So now we have gravity, hormones and sweating as factors - I would expect there is more to be learned eventually.
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Old 04-26-20, 06:11 PM
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You need to be really careful not to misinterpret or over-interpret the results of a paper

This is the conclusions of the article:

Calcium supplementation before exercise attenuated the disruption of PTH. Further research is needed to determine the effects of repeated increases in PTH and CTX on bone (i.e., exercise training), and whether calcium supplementation can diminish any exercise-induced demineralization.
It does not say or imply statement: "It turns out that bone loss in cyclists is because of sweating"

There are many factors that are at play in determining bone density or bone formation. Bone loss can happen to even people who don't sweat much. Chronic stress, which gives rise to chronicly higher cortisol levels, can negatively affect bone denisty. Takinng Ca supplementation alone does not seem halt the process of bone loss, i.e, attentuation does not mean stopping bone loss in any significant manner. Interestingly, consuming too much dairy reduces bone density; it's a great marketing campaign that milk builds bone density

Ultimately, if you're an "endurace" person who likes to do "long and low intensity" workout, you will have to deal with bone loss as part of the game.

But if you think you have bone density issue, then go to your doc and have them do a blood test for calcium. If your calcium level is within normal range, and you still have some sort of pre-osteporosis considion, then the issue may be something else. But the trend is that weightlifters and "stick and ball" sports tend to have the highest bone density among the population. Pro cyclists have lower bone density than a sedentary person; cyclists only beat out the ballerinas (ballerrinas have low bone density due to the amount of stress they have and the caloric restriction they undergo).

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Old 04-26-20, 09:13 PM
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Originally Posted by aclinjury View Post
You need to be really careful not to misinterprest or over-interpresting the results of a paper

This is the conclusions of the article:



It does not say or imply your statement of: "It turns out that bone loss in cyclists is because of sweating"

There are many factors that are at play in determining bone density or bone formation. Bone loss can happen to even people who don't sweat much. Chronic stress, which gives rise to chronicly higher cortisol levels, can negatively affect bone denisty. Takinng Ca supplementation alone does not seem halt the process of bone loss, i.e, attentuation does not mean stopping bone loss in any significant manner.

Ultimately, if you're an "endurace" person who likes to do "long and low intensity" workout, you will have to deal with bone loss as part of the game.

But if you think you have bone density issue, then go to your doc and have them do a blood test for calcium. If your calcium level is within normal range, and you still have some sort of pre-osteporosis considion, then the issue may be something else. But the trend is that weightlifters and "stick and ball" sports tend to have the highest bone density among the population. Pro cyclists have lower bone density than a sedentary person; cyclists only beat out the ballerinas (ballerrinas have low bone density due to the amount of stress they have and the caloric restriction they undergo).
I'm more in the camp of folks who say, "If the class of persons I belong to has a consistent health issue, then something we're all doing must be causing it. And thus if there's something which I can do to possibly ameliorate that issue, I'm going to do it." I'm not going to just give up and die without trying to do something about it, i.e. not going to wait 10 years for the results of a study to come out with results one way or the other.
One hypothesis is that prolonged or excessive sweating during exercise triggers metabolic responses that acutely activate bone resorption and, when this occurs repetitively (i.e., exercise training), could lead to bone loss. Accordingly to this model, calcium loss through sweating activates a cascade of events. Because sweat is derived from plasma, sweat losses with exercise would be predicted to trigger a decline in serum ionized calcium (iCa). Because serum calcium levels are vigorously defended, even a small decrease would trigger an increase in serum parathyroid hormone (PTH), which is a potent stimulator of bone resorption. The mobilization of calcium from the skeleton protects against a further decline in serum calcium.

Figure 1
Conceptual model showing the pathway by which exercise-induced disruptions of calcium homeostasis may trigger a decrease in BMD (Panel A), and the possible attenuation of bone resorption by supplemental calcium (Panel B; PTH, parathyroid hormone; CTX, ...Although this working model remains hypothetical, there is evidence that steps in the model are operative during exercise. Sweating during exercise has been found to cause a significant dermal calcium loss
I don't see an alternative explanation for the phenomena other than this model. Thus I don't think that one's blood calcium level sitting in the doctor's office has much to do with anything. In fact, this is the very error which led us down this path of self-injury.

Cyclists aren't the only folks to lose mineral bone density through currently unexplained mechanisms. Iraq and Afghan war veterans are also plagued with this problem. So far their attorneys have attempted to say this is due to vaccinations or exposure to various chemicals, no mechanism ever being explained. Here we have one. Here's a study of military recruits having their bone loss during training reduced by calcium and vitamin D supplementation: https://www.ncbi.nlm.nih.gov/pubmed/...?dopt=Abstract
pretty much the same as the cyclist study I linked to. I'm sure that this is just the tip of the iceberg in terms of bone loss through sweating. For too long this has been wrongly attributed to non-weight bearing exercise.
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Old 04-26-20, 09:36 PM
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Originally Posted by Carbonfiberboy View Post
...Cyclists aren't the only folks to lose mineral bone density through currently unexplained mechanisms. Iraq and Afghan war veterans are also plagued with this problem. So far their attorneys have attempted to say this is due to vaccinations or exposure to various chemicals, no mechanism ever being explained. Here we have one.

Here's a study of military recruits having their bone loss during training reduced by calcium and vitamin D supplementation: https://www.ncbi.nlm.nih.gov/pubmed/...?dopt=Abstract
pretty much the same as the cyclist study I linked to. I'm sure that this is just the tip of the iceberg in terms of bone loss through sweating. For too long this has been wrongly attributed to non-weight bearing exercise.
Those examples -- bone loss in military recruits and veterans -- tends to reinforce the theory about stress as a factor, rather than "sweating." Military duty is extremely stressful, including training where injuries usually exceed combat-related injuries.

Some of the most stressful stuff doesn't necessarily involve intense physical exercise. Some active duty personnel exercise as little as the average American, often waiting until a couple of weeks before physical fitness tests to begin jogging and exercising. Yet they experience high stress just from normal duties.

There may also be some connections to immunizations in some people. Active duty military personnel receive many vaccinations. I'm not opposed to vaccines and the benefits generally outweigh the risks. And a thorough study would be needed just to determine whether there's any evidence of a statistical connection, and whether it's mirrored in other groups with a high level of exposure to vaccines to compare bone density.

Also, I see that study is confined to Navy women recruits. That's a very limited sample group. It may indicate nothing more than the fact that women in general are more vulnerable to bone density loss. Navy boot camp is generally more physically rigorous only compared with Air Force boot camp, and nowhere near as physically demanding as Marine Corps and Army boot camp. I have women family members and friends who have served in various military branches, including the past year, and the relative physical demands have stayed about the same. Marine Corps and Army are far more physically demanding than Navy and Air Force. But the mental and emotional stress may be relatively closer.

And that study doesn't resolve the doubts about whether supplements -- calcium, Vitamin D -- actually do anything useful in older people.

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Old 04-26-20, 09:49 PM
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Originally Posted by canklecat View Post
Those examples -- bone loss in military recruits and veterans -- tends to reinforce the theory about stress as a factor, rather than "sweating." Military duty is extremely stressful, including training where injuries usually exceed combat-related injuries.

Some of the most stressful stuff doesn't necessarily involve intense physical exercise. Some active duty personnel exercise as little as the average American, often waiting until a couple of weeks before physical fitness tests to begin jogging and exercising. Yet they experience high stress just from normal duties.

There may also be some connections to immunizations in some people. Active duty military personnel receive many vaccinations. I'm not opposed to vaccines and the benefits generally outweigh the risks. And a thorough study would be needed just to determine whether there's any evidence of a statistical connection, and whether it's mirrored in other groups with a high level of exposure to vaccines to compare bone density.
Like anyone else, you are certainly welcome to ignore my post and do whatever you want.
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Old 04-26-20, 09:59 PM
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I'm not suggesting we should ignore possible solutions. But I'm still seeing no clear evidence of connections between bone density loss and any factor other than ... aging.

My endocrinologist and primary docs won't commit to saying whether my osteopenia is due primarily to my endocrine disorder, auto-immune disorder or just... aging. Probably mostly the latter.

They always ask me whether I'm really taking the prescribed supplements. In fact I'm taking more. My preferred whey protein powders include BCAA's, calcium, Vitamin D and a lot more. Subjectively speaking, my usual pre- and post-ride/workout drink mixes seem to help my energy and recovery. But there's zero evidence in my lab work and bone density scans to show any reduction in bone density loss.
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Old 04-26-20, 10:03 PM
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Originally Posted by Carbonfiberboy View Post
I'm more in the camp of folks who say, "If the class of persons I belong to has a consistent health issue, then something we're all doing must be causing it. And thus if there's something which I can do to possibly ameliorate that issue, I'm going to do it." I'm not going to just give up and die without trying to do something about it, i.e. not going to wait 10 years for the results of a study to come out with results one way or the other. I don't see an alternative explanation for the phenomena other than this model. Thus I don't think that one's blood calcium level sitting in the doctor's office has much to do with anything. In fact, this is the very error which led us down this path of self-injury.

Cyclists aren't the only folks to lose mineral bone density through currently unexplained mechanisms. Iraq and Afghan war veterans are also plagued with this problem. So far their attorneys have attempted to say this is due to vaccinations or exposure to various chemicals, no mechanism ever being explained. Here we have one. Here's a study of military recruits having their bone loss during training reduced by calcium and vitamin D supplementation: https://www.ncbi.nlm.nih.gov/pubmed/...?dopt=Abstract
pretty much the same as the cyclist study I linked to. I'm sure that this is just the tip of the iceberg in terms of bone loss through sweating. For too long this has been wrongly attributed to non-weight bearing exercise.
1. it's a hypothesis, yet you already concluded that you don't see any other possiblilty for bone loss to happen except to accept the hypothesis (which is unproven).
2. are you a subject matter expert in exercise and bone density?

Now let's discuss the military (Navy) recruit article you posted. There are serveral things to be mindful of this study:
1. it's a study consisted entirely of females, and well, females menstruate, which causes a lot of things to happen to the body, i.e, hormonal and mineral changes
2. The study mentions nothing about sweating, nothing about exercise intensity, and nothing about potential cortisol levels due to stress
3. The study states using Ca and vit D supplementation reduces bone fracture incidence by 20%. However, this also means that in 80% of the bone fracture cases, giving Ca supplementation does nothing to prevent bone facture

it is a stretch to use this Navy study to conclude that:
1. sweating causes the depletion of bone density to the extent that it would cause bone fracture
2. that using Ca supplementation would stop or reverse bone loss for an endurance cyclist

I'll repeat, be really careful about over interpretating studies.

Last edited by aclinjury; 04-26-20 at 10:14 PM.
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