Neoprene Booties or Winter Shoes

[Tim McNamara]

dvt <[email protected]> writes:

> Joshua Putnam wrote:
>> Personally, in Seattle winter weather, I usually ride with
>> waterproof fleece socks and sandals. If it actually gets cold,
>> freezing or below, I sometimes switch to heavy socks in clipless
>> combat boots.
>
> Clipless combat boots? Do you mean ordinary boots with platform or
> quill pedals? Or something else?


I belive Josh has discussed converting combat boots for use with SPD
pedals. ISTR he's got some information on the Web about it.

 

[Tim McNamara]

dvt <[email protected]> writes:

> Tim McNamara wrote:
>
>> However, if our hearts were located, say, at the position of our
>> bladders, they'd need to be much larger and have thicker walls to
>> keep our brains supplied with blood. The location of our hearts
>> high in the body is one of the things that makes bipedal locomotion
>> practical.
>
> I've often wondered about this. Your argument seems to miss one
> important fact: the blood needs to return from the feet and legs to
> the heart. From whence does this power come?

There are several factors involved. One is blood pressure, which of
course is higher in the legs. The second is the series of one-way
valves throughout the vascular system, which prevents blood in the
ascending column- the veins- from falling back down to the feet. This
reduces stress on the heart and also on the lower blood vessels. The
third is the pumping effect of muscular contractions, which helps move
blood out of the legs and back to the heart. When this action is
absent, blood does not move up out of the lower legs as readily.
Clotting may develop- this is a well-known risk for sedentary long
distance travellers such as airline passengers and car passengers-
which is called a "deep venous thrombosis" or DVT. People who stand
still for a long time- such as cashiers or machine operators- also
often have trouble with this. A similar problem in superficial veins
is called "phlebitis."

> Assuming the heart has to perform the work of returning the blood
> from the legs and feet to the heart, then it really wouldn't make
> much difference where the heart is located vertically. And assuming
> the blood flow is pretty much a closed system (if you're not
> bleeding or taking in some sort of IV fluid), the heart's work is
> minimized if the heart is located centrally. I'd say the heart is
> located pretty close to the optimal position, independent of my
> supinity (is that a word?).

Right, but the heart performs only a moderate percentage of returning
the blood from the legs- and of course can only do so when pushing
blood out into the aorta and the rest of the vascular distribution.
The structure of the vascular system is such that the load on the
heart is minimized by preventing backflow, and muscular contractions
in the extremities does the rest. The human body is an interesting
structure, in that nature has found ways to capitalize on these
opportunities in a very sophisticated way.

 

[Eagle Jackson]

I live in Seattle too and what works the best for me are Gore-Tex
socks, with a light pair of socks underneath. They keep my feet warm
and dry. I use them both on the road and mtn biking. I just smile now
as I ride through puddles with a layer of ice on top and freezing
water underneath.

Neoprene booties didn't cut it. Gore-tex socks did.

 

[Jim Smith]

Tim McNamara <[email protected]> writes:

> [email protected] writes:
>
>> On Sat, 30 Oct 2004 16:10:18 -0500, Tim McNamara
>> <[email protected]> wrote:
>>
>> [snip more reasonable physiology]
>>
>>>Why is the heart located high in the body? To reduce the distance
>>>it has to push blood against gravity. Our hearts are not designed
>>>to push blood into our feet when they are raised up in the air for
>>>long periods of time.
>>
>> The location of the heart above the diaphragm has little to do with
>> gravity--in most mammals, the division is fore and aft, not upper
>> versus lower.
>
> Ventral and dorsal, actually. Most mammals are quadrupeds. However,
> if our hearts were located, say, at the position of our bladders,
> they'd need to be much larger and have thicker walls to keep our
> brains supplied with blood. The location of our hearts high in the
> body is one of the things that makes bipedal locomotion practical.

Cephalad and caudal, actually. Ventral and dorsal refer to what are
commonly called the "stomach" and "back."

I'm not buying any of this business about the location of the heart
being relatively cephalad allowing us to ambulate bipedaly. Giraffes
don't normaly walk on two legs, but they commonly move their heads
rapidly from the ground to tree top height.

 

[Tim McNamara]

Jim Smith <[email protected]> writes:

> I'm not buying any of this business about the location of the heart
> being relatively cephalad allowing us to ambulate bipedaly.
> Giraffes don't normaly walk on two legs, but they commonly move
> their heads rapidly from the ground to tree top height.

Indeed they do, and have some rather interesting vasculature to make
this possible.

 

[Jim Smith]

Tim McNamara <[email protected]> writes:

> Jim Smith <[email protected]> writes:
>
> > I'm not buying any of this business about the location of the heart
> > being relatively cephalad allowing us to ambulate bipedaly.
> > Giraffes don't normaly walk on two legs, but they commonly move
> > their heads rapidly from the ground to tree top height.
>
> Indeed they do, and have some rather interesting vasculature to make
> this possible.

Right, so if our heart was in our feet we would just have some other
adaptation to make it all work, or so I suspect.

 

[dvt]

Tim McNamara wrote:
> I belive Josh has discussed converting combat boots for use with SPD
> pedals. ISTR he's got some information on the Web about it.

Thanks for the tip, Tim. A quick google turned up the page:

http://www.phred.org/~josh/bike/boots.html

I feel kinda stupid for not googling in the first place.

--
Dave
dvt at psu dot edu

 

[Tim McNamara]

Jim Smith <[email protected]> writes:

> Tim McNamara <[email protected]> writes:
>
>> Jim Smith <[email protected]> writes:
>>
>> > I'm not buying any of this business about the location of the
>> > heart being relatively cephalad allowing us to ambulate bipedaly.
>> > Giraffes don't normaly walk on two legs, but they commonly move
>> > their heads rapidly from the ground to tree top height.
>>
>> Indeed they do, and have some rather interesting vasculature to
>> make this possible.
>
> Right, so if our heart was in our feet we would just have some other
> adaptation to make it all work, or so I suspect.

Indeed, but our hearts are located where they are because evolution
tends to favor economical adaptations.

 

[dvt]

Tim McNamara wrote:

> dvt <[email protected]> writes:
>> the blood needs to return from the feet and legs to
>>the heart. From whence does this power come?

> There are several factors involved. One is blood pressure, which of
> course is higher in the legs.

In a closed system, the higher blood pressure at a lower point is simply
due to gravity. Gravity contributes no power to the round-trip system,
so I don't think that is the answer.

> The second is the series of one-way
> valves throughout the vascular system, which prevents blood in the
> ascending column- the veins- from falling back down to the feet. This
> reduces stress on the heart and also on the lower blood vessels.

Again, one-way valves don't contribute any power to the round-trip
system. In fact, one-way valves probably cause some loss of power. I can
see how they might reduce pressure in the lower blood vessels, but I
don't see how they help the heart make the blood flow.

> The
> third is the pumping effect of muscular contractions, which helps move
> blood out of the legs and back to the heart.

Yes, that one makes some sense. I can see where we might get some added
energy into the system from this mechanism. That simply shifts some of
the burden of blood flow from the heart to other muscles in the body. I
don't remember all the details from the great PowerCranks thread, but
this would seem to be a factor in those arguments.

> The human body is an interesting
> structure, in that nature has found ways to capitalize on these
> opportunities in a very sophisticated way.

Isn't that the truth!

--
Dave
dvt at psu dot edu

 

[Tim McNamara]

dvt <[email protected]> writes:

> Tim McNamara wrote:
>
>> dvt <[email protected]> writes:
>>> the blood needs to return from the feet and legs to the
>>>heart. From whence does this power come?
>
>> There are several factors involved. One is blood pressure, which
>> of course is higher in the legs.
>
> In a closed system, the higher blood pressure at a lower point is
> simply due to gravity. Gravity contributes no power to the
> round-trip system, so I don't think that is the answer.

"The" answer? No, I didn't say it was. Blood pressure is simply
higher in the legs because of gravity, and the blood in the legs is at
the bottom of a column of blood (in the arteries, that is; in the
veins, the pressure is much lower because the systolic pressure wave
is not transmitted well through the capllaries).

However, the heart works less hard to supply blood to the legs and
feet because it is gravity assisted in that direction; remember, the
original point to which I was replying was about recumbent riders with
their feet up high getting cold feet when riding in the winter.
Raising their legs removes the assistance of gravity in supplying
blood to the feet, hence creating a greater propensity for getting
cold. I also think his posture, being basically an abnormal one for
bipeds, increases stress on the heart which is now having to pump
blood against gravity to the brain and also to the feet.

>> The second is the series of one-way valves throughout the vascular
>> system, which prevents blood in the ascending column- the veins-
>> from falling back down to the feet. This reduces stress on the
>> heart and also on the lower blood vessels.
>
> Again, one-way valves don't contribute any power to the round-trip
> system. In fact, one-way valves probably cause some loss of power. I
> can see how they might reduce pressure in the lower blood vessels,
> but I don't see how they help the heart make the blood flow.

By segregating the column of blood into smaller units, and preventing
backflow, the pressure in the return lines (the veins) is lower than
it would be under the simple force of gravity if the column did not
have one way check valves. The valves do not add active assistance to
pumping blood (and I did not say they did), but do act to reduce the
resistance that gravity would otherwise produce. It's like reducing
backpressure in an automotive exhaust system.

From http://www.alspac.bris.ac.uk/discovery/focus2.html:

"The blood vessels operate a 'one- way' system. Arteries go away from
the heart and veins go towards the heart.

"Valves in the veins stop the blood from reversing so that the blood
can flow 'up-hill' on its way back from the feet to the heart."

>> The third is the pumping effect of muscular contractions, which
>> helps move blood out of the legs and back to the heart.
>
> Yes, that one makes some sense. I can see where we might get some
> added energy into the system from this mechanism. That simply shifts
> some of the burden of blood flow from the heart to other muscles in
> the body. I don't remember all the details from the great
> PowerCranks thread, but this would seem to be a factor in those
> arguments.

This is a well-known phenomenon in the medical field, having been
discovered (in Europe; Chinese and Muslim physicians already knew
about this) by William Harvey (1578-1657).

From
http://projects.edtech.sandi.net/brooklyn/humanbody/circulatory_system.htm:

"The high pressures generated by the left ventricle keep the
circulation moving forward through the arteries. The pressures are
much lower, however, on the venous side of the circulation. Instead of
relying on the heart, circulation on the venous side depends mostly on
the contraction of skeletal muscles which squeeze the veins and push
the blood forward. Blood always moves forward because there are one
way valves within the veins that keep the blood from backing up."

>> The human body is an interesting structure, in that nature has
>> found ways to capitalize on these opportunities in a very
>> sophisticated way.
>
> Isn't that the truth!

And is part of what makes life fascinating.

 

[Jim Smith]

Tim McNamara <[email protected]> writes:

> dvt <[email protected]> writes:
>
> > Tim McNamara wrote:
> >
> >> dvt <[email protected]> writes:
> >>> the blood needs to return from the feet and legs to the
> >>>heart. From whence does this power come?
> >
> >> There are several factors involved. One is blood pressure, which
> >> of course is higher in the legs.
> >
> > In a closed system, the higher blood pressure at a lower point is
> > simply due to gravity. Gravity contributes no power to the
> > round-trip system, so I don't think that is the answer.
>
> "The" answer? No, I didn't say it was. Blood pressure is simply
> higher in the legs because of gravity, and the blood in the legs is at
> the bottom of a column of blood (in the arteries, that is; in the
> veins, the pressure is much lower because the systolic pressure wave
> is not transmitted well through the capllaries).
>
> However, the heart works less hard to supply blood to the legs and
> feet because it is gravity assisted in that direction; remember, the
> original point to which I was replying was about recumbent riders with
> their feet up high getting cold feet when riding in the winter.
> Raising their legs removes the assistance of gravity in supplying
> blood to the feet, hence creating a greater propensity for getting
> cold. I also think his posture, being basically an abnormal one for
> bipeds, increases stress on the heart which is now having to pump
> blood against gravity to the brain and also to the feet.
>
> >> The second is the series of one-way valves throughout the vascular
> >> system, which prevents blood in the ascending column- the veins-
> >> from falling back down to the feet. This reduces stress on the
> >> heart and also on the lower blood vessels.
> >
> > Again, one-way valves don't contribute any power to the round-trip
> > system. In fact, one-way valves probably cause some loss of power. I
> > can see how they might reduce pressure in the lower blood vessels,
> > but I don't see how they help the heart make the blood flow.
>
> By segregating the column of blood into smaller units, and preventing
> backflow, the pressure in the return lines (the veins) is lower than
> it would be under the simple force of gravity if the column did not
> have one way check valves. The valves do not add active assistance to
> pumping blood (and I did not say they did), but do act to reduce the
> resistance that gravity would otherwise produce. It's like reducing
> backpressure in an automotive exhaust system.
>
> From http://www.alspac.bris.ac.uk/discovery/focus2.html:
>
> "The blood vessels operate a 'one- way' system. Arteries go away from
> the heart and veins go towards the heart.
>
> "Valves in the veins stop the blood from reversing so that the blood
> can flow 'up-hill' on its way back from the feet to the heart."
>
> >> The third is the pumping effect of muscular contractions, which
> >> helps move blood out of the legs and back to the heart.
> >
> > Yes, that one makes some sense. I can see where we might get some
> > added energy into the system from this mechanism. That simply shifts
> > some of the burden of blood flow from the heart to other muscles in
> > the body. I don't remember all the details from the great
> > PowerCranks thread, but this would seem to be a factor in those
> > arguments.
>
> This is a well-known phenomenon in the medical field, having been
> discovered (in Europe; Chinese and Muslim physicians already knew
> about this) by William Harvey (1578-1657).
>
> From
> http://projects.edtech.sandi.net/brooklyn/humanbody/circulatory_system.htm:
>
> "The high pressures generated by the left ventricle keep the
> circulation moving forward through the arteries. The pressures are
> much lower, however, on the venous side of the circulation. Instead of
> relying on the heart, circulation on the venous side depends mostly on
> the contraction of skeletal muscles which squeeze the veins and push
> the blood forward. Blood always moves forward because there are one
> way valves within the veins that keep the blood from backing up."
>

Right you are that the valves are very important to the circulation.
It is a well known fact that if one stands perfectly still the
pressure in the capillaries of the legs starts to rise after 30
seconds or so. The greater pressure allows a far greater portion of
the plasma to flow out into the interstitium. Enough volume can be
lost this way to cause a syncopal episode.

The valves also allow the diaphragm to have a pumping action during
respiration. When you take a breath, the diaphragm moves down and the
inra-abdominal pressure rises. There are no valves in the great
vessels, but the action of the valves in the legs means that the
squeezing forces the blood into the chest. At the same time that the
diaphragm is squeezing the abdomen, it is causing a decrease in the
pressure in the chest which further aids the return of blood to the
heart.

It is one of the dogmas of physiology that the heart pumps whatever
blood is returned to it. That is, the single largest factor affecting
cardiac output is venous return. If you look at a heart, there really
is not much of a mechanism for actively pumping blood into the
chambers. When the right ventricle contracts the tricuspid valve is
pulled down a bit which sucks some blood into the right atrium, but
that is about it.

 

[Robin Hubert]

dvt <[email protected]> wrote in message news:<[email protected]>...
> Tim McNamara wrote:
>
> > dvt <[email protected]> writes:
> >> the blood needs to return from the feet and legs to
> >>the heart. From whence does this power come?
>
> > There are several factors involved. One is blood pressure, which of
> > course is higher in the legs.
>
> In a closed system, the higher blood pressure at a lower point is simply
> due to gravity. Gravity contributes no power to the round-trip system,
> so I don't think that is the answer.
>
> > The second is the series of one-way
> > valves throughout the vascular system, which prevents blood in the
> > ascending column- the veins- from falling back down to the feet. This
> > reduces stress on the heart and also on the lower blood vessels.
>
> Again, one-way valves don't contribute any power to the round-trip
> system. In fact, one-way valves probably cause some loss of power. I can
> see how they might reduce pressure in the lower blood vessels, but I
> don't see how they help the heart make the blood flow.
>
> > The
> > third is the pumping effect of muscular contractions, which helps move
> > blood out of the legs and back to the heart.

In walkers and runners, at least, there is also the pumping action of
the compression of the extensive vasculature of the feet. This can be
verified by doppler bloodflow measurements. I doubt its effect in
cyclists.


> Yes, that one makes some sense. I can see where we might get some added
> energy into the system from this mechanism. That simply shifts some of
> the burden of blood flow from the heart to other muscles in the body. I
> don't remember all the details from the great PowerCranks thread, but
> this would seem to be a factor in those arguments.
>
> > The human body is an interesting
> > structure, in that nature has found ways to capitalize on these
> > opportunities in a very sophisticated way.
>
> Isn't that the truth!

I like it.


Robin Hubert

 

[LioNiNoiL_a t_Y a h 0 0_d 0 t_c 0 m]

RWM wrote:

> I live in the Seattle area where the usual winter weather is
> 45 - 55 degrees and wet. In the past I have used regular shoes
> with wool socks and neoprene booties. My feet still get cold

Back before I moved to the God-forsaken desert, I found that Neoprene
socks and gloves work better in cold & wet weather than woollies. I
bought mine relatively cheap from a kayak/canoe outfitter. I never liked
the Neoprene overbooties, though: too tight and constricting. I used
regular Burley shoe covers.

--
"Bicycling is a healthy and manly pursuit with much
to recommend it, and, unlike other foolish crazes,
it has not died out." -- The Daily Telegraph (1877)

 

[LioNiNoiL_a t_Y a h 0 0_d 0 t_c 0 m]

Tim McNamara wrote:

> Recumbent riders are in an abnormal position for locomotion

Almost as abnormal as canoeists, kayakkers, or swimmers.

--
"Bicycling is a healthy and manly pursuit with much
to recommend it, and, unlike other foolish crazes,
it has not died out." -- The Daily Telegraph (1877)

 

[Tim McNamara]

LioNiNoiL_a t_Y a h 0 0_d 0 t_c 0 m <[email protected]> writes:

> Tim McNamara wrote:
>
>> Recumbent riders are in an abnormal position for locomotion
>
> Almost as abnormal as canoeists, kayakkers, or swimmers.

Canoeists and kayakers are sitting down, and using mostly upper body
muscles (well, I've never kayaked so I don't know how much lower body
is involved- I've canoed for 30 years and there's not a lot of leg
use there). Scullers use a lot of leg, but again the orientation is
more or less normal from an evolutionary perspective. Swimmers
rarely have their legs above their hearts. And there are relatively
few equivalents of century rides for normal non-elite athletes in
canoeing, kayaking or swimming. Bicycling is a pretty unique sport
in this respect.

 

[LioNiNoiL_a t_Y a h 0 0_d 0 t_c 0 m]

>>> Recumbent riders are in an abnormal position for locomotion
>>
>> Almost as abnormal as canoeists, kayakkers, or swimmers.
>
> Swimmers rarely have their legs above their hearts.

Recumbent riders who aren't on a really extreme lowrider *never* have
their legs above their hearts while on the bike, so what's your point?

--
"Bicycling is a healthy and manly pursuit with much
to recommend it, and, unlike other foolish crazes,
it has not died out." -- The Daily Telegraph (1877)

 

[Tim McNamara]

LioNiNoiL_a t_Y a h 0 0_d 0 t_c 0 m <[email protected]>
writes:

>>>> Recumbent riders are in an abnormal position for locomotion
>>> Almost as abnormal as canoeists, kayakkers, or swimmers.
>
>> Swimmers rarely have their legs above their hearts.
>
> Recumbent riders who aren't on a really extreme lowrider *never*
> have their legs above their hearts while on the bike, so what's your
> point?

As I recall from many posts ago, that riding position was what I was
responding to.

 

[[email protected]]

On Tue, 23 Nov 2004 16:35:58 -0600, Tim McNamara
<[email protected]> wrote:

>LioNiNoiL_a t_Y a h 0 0_d 0 t_c 0 m <[email protected]>
>writes:
>
>>>>> Recumbent riders are in an abnormal position for locomotion
>>>> Almost as abnormal as canoeists, kayakkers, or swimmers.
>>
>>> Swimmers rarely have their legs above their hearts.
>>
>> Recumbent riders who aren't on a really extreme lowrider *never*
>> have their legs above their hearts while on the bike, so what's your
>> point?
>
>As I recall from many posts ago, that riding position was what I was
>responding to.

Dear Tim,

"Seat level" isn't really the same thing as heart level.

It's hard to get the bulk of your legs and feet above your
heart on any but the most extreme recumbents--think of
trying to see the road ahead.

Here's where things started just before Halloween:

http://groups.google.com/groups?q=g...=en&lr=&[email protected]

I suspect that most pictures of recumbent riders will show
that the bulk of their legs and feet are on a level with
their hearts at most and generally below the heart.
Otherwise, they'd have to be pretty much lying flat on their
backs with their feet elevated.

Carl Fogel