Long distance thru hikes and feet growth / swelling

Is it wrong to be so attracted by nerdy science arguments?

And yes Mark, it would be such an easy study to do! I wouldn't expect any great groundbreaking results, but it certainly would be cool if we DID find changes other than soft tissue expansion. Is there some micro damage that could mimic a limb-lengthening procedure? Is there something to be done to prevent foot growth in pregnancy, since this is actually quite annoying for a lot of women?

I'd want to see X-rays to do bone measurements, then MRIs to examine the soft tissue. Let me see what I can drum up before the hiking season begins! Too late for a grant for this year, but I like your kickstarter idea. A new way to do research, eh? I wonder how much prestige I'd get at my university from a kickstarter-funded research project…..

Several universities have begun to explore crowdfunding research: https://duckduckgo.com/?q=university+crowdfunding+research

I'll bite my tongue on what I think that says about the state of academic research in general, but you wouldn't be the first to do it, if you did.

I don't think Doug has any chance here : )

Jerry, I don't mind having some BPL guys fight over me……honest.

"I don't think Doug has any chance here : )"

That's only because my feet never get bigger, which might have something to do with the amount of time they spend in my mouth….

>"My cue was as soon the overturn of the Ptolemaic world view was invoked"

Yeah, that wasn't up to Roger's usual rhetorical level. As I was reading that paragraph, I thought he'd go with overturning the paradigm about ulcers (it ain't spicy foods, it's a transmittable infection by H. pylori bacteria) seeing as (1) it was recent, (2) it was in AUSTRALIA, (3) it was medical, and (4) it overturned a long-held assumption about the human body (that the stomach is too acidic to allow bacteria to survive), and (5) Barry Marshall and Robin Warren got a Nobel prize in 2005 for the discovery.

But perhaps he avoided that example because Marshall used himself as an experimental subject, infecting himself with H. Pylori. Which would imply that Roger, as our only BPL Australian (i.e. expendable) scientist, should be the one to cut off one foot as a control and hop on the remaining foot for a few thousand miles and compare the two feet afterwards.

>"when things slide into the nut job-crackpot extreme "

My cue for that is "There was this guy who developed a carburetor that was so efficient, you could bolt it on a 1972 Oldsmobile Delta 88 and get 100 mpg, but Detroit and the oil industry put out a hit on him." This is usually heard after picking up a hitchhiker on a back road in Kentucky or a state highway in Montana. The conversation also often includes references to Art Bell's radio show, black helicopters and the Trilateral Commission. It isn't hard to see how such high-functioning individual can't afford their own wheels.

Regarding the crowd-sourcing of research funding, yeah, you could start with a T-shirt, but you need to have multiple levels of rewards:

$5 – you get to read Roger's blog ruminating about his foot growth during his next long hike
$25 – you get the blog AND a cheap T-shirt
$100 – you get one of Roger's stoves
$500 – you also get one of Roger's tent's
$1000 – all of the about and you DON'T have to smell Roger's feet at the end of said hike.

I too thought Roger's original comment was a bit harsh

And then, the next day he "doubled down" with another

But, mostly, I was just trying to come up with some clever line about how he should remove the offending text and put in something like "removed by moderator, isn't that a bit harsh?" : )

I think Bob G made a good point some distance back. he pointed out that I am saying that an increase in foot size after long walks does happen, while Jennifer is saying that bones don't keep growing in length after adulthood is reached. The two are different things. They may not be in conflict.

I did suggest that maybe what we are seeing could be cartilege growth rather than bone growth. This could be a moderately new idea. Mark suggested:
"Most medical research is on pathologies, so it may be that no one has ever specifically looked at what happens with before and after very long periods of walking using MRIs or X-Rays of the foot. It would seem to be a hole in the research in the sense that to resolve the large scale physiological changes would be easy today, if not the mechanisms responsible for the changes.

I am personally not interested in having lots of X-rays taken as there is a medical risk with the radiation. Unfortunately, carting an fMRI to a trackhead seems unlikely in the extreme. Perhaps some simpler measurements using some sort of cheap jig might be possible? If the jig was well-described (in engineering terms), many copies could be made.

There does seem to be a widespread concensus that in many cases our feet do grow after a long thru-hike, on a permanent basis. It is also well-known that feet do swell up by the end of just one day of walking, although this is usually not permanent. But going any further requires real measured data, not my waffle. What can we measure?

You know, just using something like a Brannock Device to measure length and width would be a start. If you could add something to measure the height of the top of the arch that would be good. And maybe you could measure foot volume with a bucket of water (Archimnedes-style).

Grant applications?

Cheers

What happens with giantism, do the growth plates of the long bones not get closed up? Reason why I ask is because these folks continue to grow until their bodies can't support it anymore.

"I think Bob G made a good point some distance back."

I've even forgotten whether that was some distance in miles or kilometers.

There are lots of soft tissues in feet. With mine, the dimensions come and go with the seasons, and whether my body weight is going up or down.

–B.G.–

If scout and Frodo helped out in San Diego and then the same hikers measured at the dinsmores at Steven pass then you would have the answer.

"There are lots of soft tissues in feet. With mine, the dimensions come and go with the seasons, and whether my body weight is going up or down."

And whether or not you remember to trim your toenails, a point so far overlooked in this learned discussion. ;0)

>"And whether or not you remember to trim your toenails"

And to include a bit of actionable information, something I first saw on a GCNP hikers' blog:

Don't cut your toenails very far back just before a trip. Do it in smaller steps and finish doing it a week before you go. So the newly exposed tissue isn't exposed to the extremes of pressure, temperature and dirt right away.

I trim my toenails at the trail head and have never had a problem.
On longer trips I take tiny scissors to trim as I go.

b

Walkers are not the only one to be preoccupied with their feet. Ballet dancers are even worse. See:
http://lens.blogs.nytimes.com/2013/12/30/at-city-ballet-footwear-is-almost-as-important-as-feet/?src=me&ref=general

Cheers

Interesting question…

These disorders are caused by excessive growth hormone – if it happens before the growth plates close it is called gigantism and the patient becomes very, very tall very quickly. In this a case they do stop gaining height once the growth plates close. If the disorder appears (or continues) after the epiphyseal plates close then it is known as acromegaly (remember Andre the Giant?). This is characterized by continued bone thickening, not lengthening (although excess growth hormone while the epiphyseal plates are changing do cause them to be excessively tall).

Here is a nice article with more or less detail, depending on what interests you.

http://emedicine.medscape.com/article/925446-overview

Thanks Jennifer for the reference to Physiology of Bone Formation, Remodeling, and Metabolism by Usha Kini and B. N. Nandeesh. I read through it and took some notes, and then followed up with some other readings. My notes are are a bit long-winded as they are mostly quotes. For those who don't want to wade through them, I have put them at the end.

It seems to me that while 'bone growth' per se may cease at puberty as you have suggested, 'bone remodelling' can continue for all your life. What's more, this 'remodelling' can add to the bone size if that is what is needed to reinforce the bone to withstand the stresses. Two interesting conclusions I drew from several references are that first, what matters are cyclic stresses (as in walking) rather than static ones, and secondly the stresses encountered in 'ordinary life' are probably not significant. The corollary to the second is that very little study has been done on the response to much higher cyclic stresses over long periods, but what there is suggests it can be significant.

I note that bone remodelling does depend on (start with) collagen to a high degree. We have observed on many trips that after a few weeks walking our skin becomes more healthy and any wounds (cuts, scrapes etc) simply vanish in a day or two. This suggests that sustained walking beyond several weeks is boosting the collagen processes in our bodies, and this could influence bone remodelling.

Observation by many suggests that foot length grows a little bit but foot width grows a lot more. This would be consistent with the idea that bone remodelling is what is happening, since that seems to focus mainly on bone diameter rather than length.

As far as I could see, there has been almost no research on the physiological response to sustained long-distance walking by adults. Studies on babies and juveniles, on a few sedentary adults, or even on a few post-mortem bones: lots of that. In fact, some of the published articles did note this lack, but the authors did not seem inclined to pursue the matter.

Room for research!
Cheers

p 29:
Bone constantly undergoes modeling (reshaping) during life to help it adapt to changing biomechanical forces, as well as remodeling to remove old, microdamaged bone and replace it with new, mechanically stronger bone to help preserve bone strength.

p37:
Bones normally widen with aging in response to periosteal apposition of new
bone and endosteal resorption of old bone. Wolff’s law [see below] describes the
observation that long bones change shape to accommodate stresses placed on
them. Bone modeling is less frequent than remodeling in adults (Kobayashi
et al. 2003 ) .

p42:
2.4 Bone Remodeling
Bone remodeling is a lifelong process wherein old bone is removed from the
skeleton (a subprocess called bone resorption), and new bone is added (a
sub-process called ossification or bone formation). Remodeling involves
continuous removal of discrete packets of old bone, replacement of these
packets with newly synthesized proteinaceous matrix, and subsequent
mineralization of the matrix to form new bone
(Fernández-Tresguerres-Hernández-Gil et al. 2006 ; Fraher 1993 ). These
processes also control the reshaping or replacement of bone during growth
and following injuries like fractures but also microdamage (prevents
accumulation of bone microdamage through replacement of old bone with the
new one) (Turner 1998 ) which occurs during normal activity. Remodeling
responds also to functional demands of the mechanical loading. As a result,
bone is added where needed and removed where it is not required. This
process is essential in the maintenance of bone strength and mineral
homeostasis. The skeleton is a metabolically active organ that undergoes
continuous remodeling throughout life.

p 43:
The bone remodeling cycle involves a complex series of sequential steps
(coupling of bone formation and bone resorption). Bone balance is the
difference between the old bone resorbed and new bone formed. Periosteal
bone balance is mildly positive, whereas endosteal and trabecular bone
balances are mildly negative, leading to cortical and trabecular thinning
with aging. These relative changes occur with endosteal resorption
outstripping periosteal formation.
The main recognized functions of bone remodeling include preservation of
bone mechanical strength by replacing older, microdamaged bone with newer,
healthier bone and calcium and phosphate homeostasis. The relatively low
adult cortical bone turnover rate of 2–3 %/year is adequate to maintain
biomechanical strength of bone. The rate of trabecular bone turnover is
higher, more than required for maintenance of mechanical strength,
indicating that trabecular bone turnover is more important for mineral
metabolism.

p47:
2. Mechanical Factors
Remodeling is regulated by mechanical loading, allowing bone to adapt its
structure in response to the mechanical demands. Physical activity is
essential for the correct development of bone. It is believed that muscular
action transmits tension to the bone, which is detected by the osteocyte
network within the osseous fluid. On the other hand, the absence of
muscular activity, rest, or weightlessness has an adverse effect on bone,
accelerating resorption. It is well-known that trabeculae tend to align
with maximum stresses in many bones. Mechanical stress improves bone
strength by influencing collagen alignment as new bone is being formed.
Cortical bone tissue located in regions subject to predominantly
tensile stresses has a higher percentage of collagen fibers aligned along
the bone long axis. In regions of predominant compressive stresses, fibers
are more likely to be aligned transverse to the long axis.

p52:
Collagen is the major structural protein of bone and comprises about 90 %
of the organic material. Collagen clearly contributes to the integrity
and strength of bone matrix, and defects in its production, for example, in
osteogenesis imperfecta, leads to bone of poor quality, susceptible to fracture.

Wolff's law is a theory developed by the German anatomist and surgeon Julius Wolff (1836–1902) in the 19th century that states that bone in a healthy person or animal will adapt to the loads under which it is placed.[1] If loading on a particular bone increases, the bone will remodel itself over time to become stronger to resist that sort of loading.[2] The internal architecture of the trabeculae undergoes adaptive changes, followed by secondary changes to the external cortical portion of the bone,[3] perhaps becoming thicker as a result. The inverse is true as well: if the loading on a bone decreases, the bone will become weaker due to turnover, it is less metabolically costly to maintain and there is no stimulus for continued remodeling that is required to maintain bone mass.[4]

Mechanotransduction

The remodeling of bone in response to loading is achieved via mechanotransduction, a process through which forces or other mechanical signals are converted to biochemical signals in cellular signaling.[5] Mechanotransduction leading to bone remodeling involve the steps of mechanocoupling, biochemical coupling, signal transmission, and cell response.[6] The specific effects on bone structure depends on the duration, magnitude and rate of loading, and it has been found that only cyclic loading can induce bone formation.[6] When loaded, fluid flows away from areas of high compressive loading in the bone matrix.[7] Osteocytes are the most abundant cells in bone and are also the most sensitive to such fluid flow caused by mechanical loading.[5] Upon sensing a load, osteocytes regulate bone remodeling by signaling to other cells with signaling molecules or direct contact.[8] Additionally, osteoprogenitor cells, which may differentiate into osteoblasts or osteoclasts, are also mechanosensors and may differentiate one way or another depending on the loading condition.[8]
[My bolding]

Basic Multicellular Unit-based bone remodeling can lead to the removal or conservation of bone, but cannot add to it. Decreased mechanical usage (MU) and acute disuse result in loss of bone next to marrow; normal and hypervigorous MU result in bone conservation. Bone modeling by resorption and formation drifts can add bone and reshape the trabeculae and cortex to strengthen them but collectively they do not remove bone. >b>Hypervigorous MU turns this modeling on, and its architectural effects then lower typical peak bone strains caused by future loads of the same kind to a threshold range. Decreased and normal MU leave this modeling off. Where typical peak bone strains stay below a 50 microstrain region (the MESr) the largest disuse effects on remodeling occur. Larger strains depress it and make it conserve existing bone. Strains above a 1500 microstrain region (the MESm) tend to turn lamellar bone modeling drifts on. By adding to, reshaping and strengthening bone, those drifts reduce future strains under the same mechanical loads towards that strain region. Strains above a 3000 microstrain region (the MESp) can turn woven bone drifts on to suppress local lamellar drifts but can strengthen bone faster than lamellar drifts can. Such strains also increase bone microdamage and the remodeling that normally repairs it. Those values compare to bone's fracture strain of about 25,000 microstrain.

Excellent thread!

My 2c
First I note that weight bearing exercise is recommended to elderly women to help prevent hip fractures. I suppose that this exercise increases bone strength by increasing bone diameter.

2nd here is another way feet can grow. This is my heel, note the bump on the right side. This is a bone spur that has grown over time at the attachment point of the achillies tendon and has effectively increased the length of the foot.

Stuart, great comment about the heel bump. This is an osteophyte (also known as an exostosis – an abnormal bone growth) like I mentioned earlier…so thanks for the picture… That is a huge reason why people need longer shoes…they can literally be inches long in some people. Here is what it looks like in an X-ray:

And to clarify a point in Roger's book quotes…and for the sake of my orthopedic professor duties…bones GENERALLY do not grow in diameter, but rather in density. The "trabecular" bone mentioned in the chapter Roger is quoting from is the mesh-looking filler inside the bone itself:

I used a picture of the hip (this is the head of the femur) because this is the clearest example of the lines of force in trabecular bone. Pretty cool, eh?

Those tiny lines you see actually change their direction depending on the forces involved. When people have osteoporosis it's here that can nearly disappear…that is what we mean by "bone density." Wolff's law, as Roger quoted, is the adaptation of any tissue to stress, including bone. The cortical bone can thicken (that's the solid bone that forms the outer layer of the bone), and the trabecular lines inside become more dense and form in the direction that counters the stress imposed on the bone.

So in response to repeated stress a few things can happen: most common is an increase in density of the inside of the bone, and a thickening of the cortical bone on the outside (and generally, in the absence of pathology, the bone does not become significantly larger in diameter); or you can develop exostosis (sometimes called osteophytes, or bone spurs) as the body attempts to strengthen itself along the line of force.

Thank you for the info Jenn.

Hi Jennifer

Fascinating X-ray pic! Thanks.

> bones GENERALLY do not grow in diameter, but rather in density.
Point taken, but I wonder how much research has been done on the effects of a 2 month long thru-hike? I suspect we are talking here about an extreme case, not an average case, and one which few (if any) researchers have ever encountered. Maybe there is room here for original research which could expand our knowledge?

An impression I did get from my reading was that you need cyclic stress (OK) at a high level (OK) over a long time (several weeks?) to get some of the extreme effects. Ordinary medical research never sees this sort of stuff.

Cheers

"Ordinary medical research never sees this sort of stuff."

Even ordinary medical clinics do not see this sort of stuff.
I was in for minor surgery last spring and they are amazed at my resting pulse, BP, low weight, muscle developmentfor my age, and the fact that I don't take any prescription drugs regularly. The doctor commented to the OR staff just before they put me under that I was the healthiest and fittest person they had seen of any age in the past several months… or more. And I really don't consider myself super fit.

Billy

There is an idea, Roger. You can get an MRI machine and keep it in the shop with your CNC milling machine. You can get a scan and a gear touch-up before each trip.

–B.G.–

"The doctor commented to the OR staff just before they put me under that I was the healthiest and fittest person they had seen of any age in the past several months… or more."

That is standard procedure. It makes the surgical patient believe that they care.

Let them put you through a treadmill test.

–B.G.–

"Let them put you through a treadmill test."

Had that experience about 30 years ago. The Argentine government required stress EKGs (while on treadmill) in order to get permits to climb Aconcagua (just shy of 23,000 ft).

The doctor, who was a runner, was monitoring the treadmill and the EKG while I was running commented to the nurse after he had increased the incline and speed several times, "I would have collapsed about 20 minutes ago."

Billy