[pct-l] Ankles

Sun Feb 27 18:00:11 CST 2011

Thanks,  greg

It seems to be the same old dispute. People tend to think within their
experience. But, personal experience do not always disclose the truth.

I have found three good scientific papers.  Of course, there are many
wrong scientific papers, so we need to be careful to evaluate their
results.

-----This paper indicated that the ankle fixation do not increase
energy expenditure. Experimental research ( single group )

Gait Posture. 2008 Oct;28(3):427-33. Epub 2008 Mar 24.
Ankle fixation need not increase the energetic cost of human walking.
Vanderpool MT, Collins SH, Kuo AD.
Department of Biomedical Engineering, University of Michigan, Ann
Arbor, MI 48109-2125, USA.
Abstract
We tested whether the metabolic energy cost of walking with the ankles
immobilized can be comparable to normal walking. Immobilization of any
lower extremity joint usually causes greater energy expenditure.
Fixation of the ankle might be expected to eliminate the work it
normally performs, to detrimental effect. But fixation using
lightweight boots with curved rocker bottoms can also bring some
benefits, so that the overall energetic effect might be quite small.
We measured oxygen consumption, kinematics, and ground reaction forces
in six (N=6) able-bodied human volunteers walking at 1.25 m/s in three
conditions: normal walking in street shoes, walking with ankles
immobilized by walking boots, and normally with ankles free but also
weighted to match the mass of the walking boots. We estimated
metabolic energy expenditure, joint work, and overall work performed
on the body center of mass as a function of ankle fixation. Ankle
fixation with walking boots caused the total rate of energy
expenditure for walking to increase by 4.1% compared to normal
(P=0.003), but differed by an insignificant amount (0.4% less, P=0.78)
compared to walking with equivalent ankle weight. Compared to normal
walking, ankle fixation can reduce ankle torque and work during the
stance phase, most notably during late stance. This apparently makes
up for the loss of ability to push-off as normal. With a suitably
lightweight apparatus and curved rocker bottom surface, loss of ankle
motion need not increase energy expenditure for walking.

-----This paper disclosed that the  high-top shoes deduced the
Achilles tendon loading. This paper adopted good experimental design
(matched pare comparison trial),  so the conclusion of this study may
be  trustful.

Clin J Sport Med. 2010 Sep;20(5):344-9.

Can footwear affect achilles tendon loading?
Rowson S, McNally C, Duma SM.
Center for Injury Biomechanics, Virginia Tech-Wake Forest University,
Blacksburg, VA, USA. srowson at vt.edu

Abstract
OBJECTIVE: To investigate the effects of footwear on Achilles tendon
tension by directly measuring Achilles tendon tension and dorsiflexion
range of motion.
DESIGN: A total of 48 matched pair tests were performed comparing the
effects of shoe type (high-top vs low-top) for each shoelace
configuration (tied vs untied). These were performed using the
Achilles tendons of 4 human cadaver lower extremities that were
instrumented with a customized load cell designed to measure tension.
The lower extremity was inverted in a custom testing apparatus
designed to inertially invoke dorsiflexion of the foot, putting the
Achilles tendon in tension.
SETTING: Research laboratory.
PATIENTS: Left and right lower extremities of 2 human cadavers.
INTERVENTIONS: None. Independent variables were shoe type and shoelace
configuration.
MAIN OUTCOME MEASURES: Achilles tendon tension and dorsiflexion range of motion.
RESULTS: High-top shoes significantly reduced peak Achilles tendon
tension by an average of 9.9% when compared with low-top shoes. Tied
laces significantly reduced peak tension for low-top (3.7%) and
high-top (12.8%) shoes when compared with untied laces. With tied
laces, high-top shoes significantly reduced peak dorsiflexion angle by
an average of 7.2% when compared with low-top shoes. Tied laces with
high-top shoes significantly reduced peak dorsiflexion angle by an
average of 4.7% when compared with untied laces. A P value of 0.05 was
determined to be significant.
CONCLUSIONS: This study offers valuable insight that footwear can
affect Achilles tendon loading during dorsiflexion.

------ When we wear boots, the joint loading at the knee might be increased.

J Biomech. 2010 Sep 17;43(13):2467-72. Epub 2010 Jun 11.
Effect of boot shaft stiffness on stability joint energy and muscular
co-contraction during walking on uneven surface.
Böhm H, Hösl M.

Gait Laboratory, Orthopedic Hospital for Children, Bernauerstr. 18,
Aschau i. Chiemgau, Germany. boehm at mytum.de

Abstract
Increased boot shaft stiffness may have a noticeable impact on the
range of motion of the ankle joint. Therefore, the ability of the
ankle joint to generate power for propulsion might be impaired. This
might result in compensatory changes at the knee and hip joint.
Besides, adaptability of the subtalar joint to uneven surface might be
reduced, which could in turn affect stability. The aim of the study
was therefore to investigate the influence of boot shaft stiffness on
biomechanical gait parameters. Fifteen healthy young adults walked
over coarse gravel wearing two different hiking boots that differed by
50% in passive shaft stiffness. Leg kinematics, kinetics and
electromyography were measured. Gait velocity and indicators for
stability were not different when walking with the hard and soft boot
shaft over the gravel surface. However, the hard boot shaft decreased
the ankle range of motion as well as the eccentric energy absorbed at
the ankle joint. As a consequence, compensatory changes at the knee
joint were observed. Co-contraction was increased, and greater
eccentric energy was absorbed. Therefore, the efficiency of gait with
hard boots might be decreased and joint loading at the knee might be
increased, which might cause early fatigue of knee muscles during
walking or hiking. The results of this study suggest that stiffness
and blocking of joint motion at the ankle should not be equated with
safety. A trade-off between lateral stiffness and free natural motion
of the ankle joint complex might be preferable.

2011/2/28 greg mushial <gmushial at gmdr.com>:
>> Message: 1
>> Date: Sat, 26 Feb 2011 21:22:15 -0800
>> From: Eric Lee <saintgimp at hotmail.com>
>> Subject: Re: [pct-l] Ankles
>> To: "'CHUCK CHELIN'" <steeleye at wildblue.net>, "'PCT listserve'"
>> <pct-l at backcountry.net>
>> Message-ID: <BAY145-ds58A75378F235D5E51F142BDDF0 at phx.gbl>
>> Content-Type: text/plain; charset="us-ascii"
>>
>> Steel-Eye wrote:
>>>
>> Diane is correct in her assessment that typical hiking boots contribute
>> little, or nothing, to resist ankle-turning.  The low style boots are
>> about
>> 6" in height.  Medium heights are maybe 8" high.  Neither is much higher
>> than the distance from the ground to the center of the ankle joint and
>> they
>> won't contribute significantly to absorbing torque about the ankle
>> regardless of how tightly they are laced.  They may feel nice and snug and
>> firm - a physiological advantage - but they will not significantly resist
>> even a mild turn, let alone a 2g - 3g turn possible with a misstep on the
>> trail.
>>>
>
> Eric - I believe there is an additional factor which has gone unmentioned:
> that is the leverarm effect. The force exerted against one's ankle in the
> rolling under process, is applied via a leverarm, namely that part of the
> foot below the ankle. This leverarm effect is offset by the width of the
> foot, ie, a broad base resisting any  rolling laterally. It seems as the
> boots get heavier, the thickness of the soles increases, or more
> importantly, that leverarm distance, from the ground to the ankle is
> increased...  making it easier to twist an ankle, or said differently,
> making it more difficult for the connective tissue of the ankle to resist
> being turned under. This is way I've gone with two types of walking shoes:
> one with micro thin soles, which do not contribute to this leverarm length;
> and boots with incredibly stiff sides (typically mountineering boots), which
> because of the increased leverarm length, would be more inclined to twist
> ankles, but because of the stiffness, that tendency is more than offset. In
> my book, the worst ankle twisters are the boots with very thick soles (ie,
> lengthened leverarm distance), but with thin soft almost glove leather
> (offering no additional resistance to rolling under)...  in my book they're
> an accident waiting to happen. I've noticed this same effect in running
> shoes with exaggerated soles - equally deadly.
> TheDuck
>
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-- 
Sincerely
--------------- --------------------------------------
Hiro    ( Yoshihiro Murakami )
Blogs http://completewalker.blogspot.com/
Photo http://picasaweb.google.co.jp/CompleteWalker/
Backpacking since about 1980 in Japan
2009 JMT, the first America.
2010 JMT, the second America.
------------------------------------------------------