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Letter to Editor in MSSE regarding conflict of interest in biomechanics.



Copyright 10 1992 by the American College of sports Medicine

Vol. 24, No.1

Printed In U.S.A.


 Editor's Note:

 Drs. Robbins and Gouw hav e chosen to raise the

issue of the conflict of interest policies of the Journal

and imply that the Journal should police letters written

to the Editor-in-Chief. In  the Informa tion for A uthors

 section of this issue of the Journal the " conflict of

i nterest" regarding published peer reviewed manuscripts

has been addressed after receiving editorial board

approv al and reflects a y ear-long rev iew of the policy.  I

reject Drs Robbins and Gouw' s expectation that the

Editor-in-Chief should impose this polic on letters to

the editor.

Historically I have had to respond to a letter of

complaint from Robbin and Gouw c onc erni ng one of

their rejected manusc ripts. I n thi complain they a lso

raised t he issue of c onflic t of in te rest by t he rev iew ers,

 as being the reason for the rejecti on of the ir manus cript,

 even though they w ere bli nd as to whom the rev ie wers

were. Neither Drs. F re deri ck or C av anagh were reviewers

on the re jected manusc ript Furthermore, rev iew ed

their conc erns regarding t he ir manusc ript a nd found

thei r charges o conflict of i ntere st t o be unf ounded.

Clearly thes two l etter need to be r ead with a

critical ey e to th sci ence bei ng dis cuss ed and on needs

to ref rain from bein g draw n into pers ona differe nce s.

 I c an assur e th reader s that the s two le tters will be the

only ones publis hed o n the issues raised by Drs. Frederick

and Cavanagh.

 Dear Editor-in-Chief:

Dr. Steven Robbins has been republishing the same

editorial seasoned with a pinch of new data for the last

several years and we are distressed to see y et another

appearance in MSSE CMSSE  23:2 17 1991). Dr Robbins'

main contention is that sport shoes affect the

pattern of movement in a way that is unsafe. He

presents data showing the effect of shoe sole materials

on the mechanics of mov ement. Although Robbins

wishes to extrapolate his data to actual running, his

results are collected in a laboratory setting that involves

contrived quasi-static movements and atypical limb

postures rather than actual studies of runni ng mechanics.

 Further t o the poin t Dr. Robbins' arguments re st

heavily on the notion that informati on from cutaneous

receptors are the only data that the body uses to monitor

potentially damaging ;)trC ;);)CT5.his assertion is untenable

and unproven. These facts combine d with the inappropriate

kinetics used in Robbins' c xpcr ime nte conspires

to make his results of limite d use in an understanding

of running mecnamcs or any other vlaorous

 athletic movement.

 Some runner snectnc  technical Ilmitat ions we o bserved

 of which we fed y our reade rs should be aware.

The spec ification of me chanical inputs in unit of kg.

crr r i misle ading This is presumabl the pressure in

the authors' pneumatic actuators and is certainly not

the pressure applied to an part of the body . To q uote

these figures in the abst ract  i meanin gless  since  the

 result of s uch an input is s pecifi c to t he re searcher' s

apparatus Thi s confusion seems to persis as the authors

go on t o ex trapolate about possible vertical loads

 in r unni ng of 1.03 kg cm" . T he pla ntar pressures

 duri ng actual run ning ar at least 10 time s this v alue

 when measured on the bare foo t. T here is also some thing

peculia about the straight lines in Figure 4 and

the das hed ext rapolation int load ra nges "s ee n in


 The opening line of th discus sion is blatant misstatement:

"This experiment relates pla nta lo ad during

locomotion and jump ing and plantar discomfort w hen

shod and unshod." It  does nothing o the ki nd.

 Despit th limited usefulness of hi data researcbers

 lik us, who study footwear biomechanics ar e generally

intrigued b man of Dr. Robbi ns ob serv ation about

footwear-induced kinematic changes, bUI  we s trongly

 disagree w ith his as se rtion tha t sport shoes hav e been

shown to be unsafe,  or less injurious than barefoot


 I is impor ta nt to point out that hi conclucion that

wear ing ehoee i s " unsafe is not base d on hi s own data,

 but is largely bncsd on ~ selective and rather c areless

 reading o the literature on me ernuermotoa oroveruse

 injuries in sport. F urthermore Robbin bla tant l miscites

sev eral biomec hanica l st udies as  supporti ng his



 contention that sport shoes are unsafe. No data are

presented nor are any conclusions drawn in any of the

biomechanical studies cited by Robbins on the question

of the safet of sport shoes.

Dr. Robbins misrepresentation of the literature he

cites is  almost universal. few of many examples:

Robbin s cites Casperson et a l. (Med. Sci. Sports Exerc.

 16:113 1984) vs Marti et al. (Am. J. Sports Med.

 16:285-294 1988) to show a trend toward an increase

in running injuries over the y ears when in fact these

studies cover overlapping time periods. Casperson's

work (a very brief abstract that did not  mention footwear)

was published in 1984 and covers participants in

a 1983 race. And although the Marti research Dr.

Robbins cites in support of his contention that shoes

are uns afe was published in 1988 in fact the surv ey

was done in 1984 and was based on running injuries

experienced during 1983-84.

Further to the point Marti' s research presents no

 data to show that shoes are unsafe but he did find a

statistically signific ant "preventive effect from the use

of shoe inserts-a point that clearly contradicts Robbins'

assertions but which he conveniently overlooks.

Dr. Robbin further cites Marti as showing that runners

who wear more expensive shoes (>$40) are more frequently

injured, but Marti c learl point out that this

is an " incorrect conclusion Only 2.7%  of his sample

w ore shoes under $40 in cost raising the suspicion that

the finding of fewer injuries in this small group is an

artifact due to age and income differences (i.e. Marti

reports that runners wearing these less expensive shoes

tended to b young people and therefore more free of

injury ).

 This kind of inat tention to detail and a willingness

on Dr. Robbins part to overlook evidence that does not

support his point of view is a thread that runs through

this paper and his other recent publications. This is not

an acceptable practice and we believ e we would have

hoped that such careless and irresponsible science

would have been uncovered during the review process.

 Furthermore it is our opinion that the title of Dr.

Official Journal of the American College of Sports Medicine  145

Robbins article was misleading and should not have

gone unchallenged during the rev iew pro cess He refers

to athle tic shoes in the title as "unsafe. His report,

however, has nothing 10  do with safety has littl to do

with athletic shoes and presents no data that can be

interpreted as even indirectly supporting s uch a conclusion.

 No original data on sports shoe safety are presented,

only data on artificial motor behaviors that

hav e not been shown to occur in actual running and

which have not been shown to be unsafe by him or any

other researcher. In light of the absence of any data to

support Dr. Robbins conclusions we are troubled by

his outrageous allegation that manufacturers of athletic

footwear are "irresponsible for representing their products

as offering improved protection In fact, he further

emphasizes the absurdity of his a llegations by attacking

existing "safety standards" for footwear when in fact

everyone who works in this area knows that there are,

 as yet no such standards.

The biomechanical interactions between the body

and the shoes and surfaces ove r whic h we run is an

important topic for study . It promise to lead us to new

ideas about the causes of overuse injuries, and it may

 result in new strategies for their treatment and prevention.

But such careless and nonscientific soap-box oratory

 will not bring us an of these positive benefits and

in fact may result in more harm and misunderstanding.

As a  result of his research Dr. Robbins makes the

outrageous and untenable recommendation of "barefoot

activity-where practical and sociall acceptable."

As readers of this widely read journal we simply can

not let stand such a radical and potentially harmful

conclusion in the advance of any data to support it.

E C. Frederick Ph.D.


Exeter Research Inc.

Peter R.  Cavanagh Ph.D.

Professor and Director

Center for Locomotion Studies

Pennsy lv ania State University


 Dear Editor-in-Chief:

T his response to Frederick  and Cavanaan' le tter

provides !l  lone awaited opportunit to deal with c on·

tltct of interact it pertains to scientific publications.

 which M!:  concerned us for some time, We  first will

de!!] with specific points they raise.

It should be made clear that to in validate  our position

that the modern running shoe is unsafe, two conditions

must be  met. First data must be produced suggesting a

lower injur frequency with modern shoes lower impact

during  running with these footwear, or  showing

expensive shoes (advertised as offering increased OfOtection:

e.g.,  increased cushioning "pronation corrccnon")

 protect better than inexpensive ehocs. Frederick

 and C avanagh render no references suggc;:,tingthis be cause

none exist.

 Second they must provide conv incing arg uments

 that our citations and data suggesting that these footwear

are hazardous, and our causality theor are in

146 Official Journal of the American College of Sports Medicine

 error. We provided 15 references indicating safety COncerns,

and 16 that support our causality theory (6).

Despi te their inflated rhetoric, they question only two

(1,3) of these 31 citations. Evidently they found no fault

with the remaining 29, because if further data were

available to fortify thei r anemic arguments they surely

would have used them For example, they concede

impact during running is at its highest when runners

use the softest soled shoes (5) and impact is invariably

20-25% greater when gymnasts land on thick soft mats

when compared with hard surfaces (4). We encourage

readers to seek out these citations.

As for the two references they question, they contend

we mislead because the time interval between Caspersen

et al.'s (1) and Marti et al.'s (3) collection of data was

shorter than what might be assumed from the publication

dates. No statement in our report specified this

interval because Caspersen et al.'s report, which we

(and they) refer to does not mention dates (6). Since

Frederick and Cavanagh provide no reference offering

this date this claim can be dismissed.

They argue that we do not report references that are

contrary to our position-an audacious allegation COnsidering

no example follows. We (and perhaps they) are

aware of no published report that does not support our


Frederick and Cavanagh's assessment of Marti's work

is fiction (2, 3). Of the 5,026 respondents in his study,

inexpensive shoes «US $40) were worn by 311

(6.2% -not 2.7%) and 260 (5.1%) wore expensive ones

(>US $95). Their respective frequency of injuries per

year corrected for training mileage was 14.3 and 31.9-

123 greater injury frequency with expensive shoes.

Differences of this magnitude (P < 0.05) are not easily

dismissed as the work of statistical gremlins as they

unconvincingly attempt. Obviously features present in

expensive footwear are injurious. If this relation between

footwear cost and injury frequency were extrapolated

upward linearly, athletic footwear costing more

than US ' $300 could come with a guarantee of at least

one injury per year. This adds novel meaning to the

notion of getting value for one' s money We believe

Marti's work, as well as the 14 other references, support

our conclusion: "Based  on the above data notwithstanding

unsupported claims by footwear manufacturers

of improved protection with their products it seems

appropriate to consider expensive running shoes from

major manufacturers (and perhaps less expensive shoes)

as unsafe."

In re lation to footwear safety standards Frederick

and Cavunagh contend, "everyone who works in this

area knows there  are, as yet, no such standards. This

is nonsense. Our group has voting representation on

the following committees American Society for Testing

of Materials (ASTM) Group F08 Sport Equipment and

Facilities ASTM F08. 54 Athletic Footwear ASTM F-

13 Safety and Traction in Footwear; American National


 Standards Institute (ANSI) Z41 Performance Requirements

for Protective Occupational Footwear. Each has

advanced footwear safety standards, but as stated in

our text, "they are inadequate because they do not

account for the discomfort-impact illusion." We have

always thought that injury incidence can be reduced

through footwear modifications (6-11) and have

worked toward this goal through the above organizations.

Their lack of knowle dg of these groups let alone

not being participating members indicates that their

passion concerning athletic footwear user safety is less

than consuming.

 They argue that plantar perception during locomotion

bears no relation to plantar sensibility at rest yet

provide no data o reference to support this. It is

preferable in physiological research to simulate as

c1os~ ly as possible natural conditions which we mentioned

in our text as a limitation However this shortcomi ng

is shared by all experimental research which is

usu~l ly performed in a laboratory, and controls variables

not controlled in nature. Surely the do not

belier ve all experimental research-including their

own-is invalid Furthermore, we do not believe it is

feasible to accurately measure perception of plantar

load during actual running Without providing a

method, their comment is no more than empty rhetoric.

They misquote us. It should read (6) "Barefoot activity

when practical (no need for thermal insulation;

no risk of crush injuries social acceptability) deserves

consideration since plantar sensory mediated protective

adaptations seem optimized for this condition. Although

this may run counter to notions prevalent in

economically advanced countries recounting the dangers

of barefoot activity and necess ity of footwear even

when barefoot activity is feasible supporting data are

lacking, and many have c oncluded that footwear design

is guided by fashion rather than health considerations."

 We stand behind the above statement and Frederick

and Cavanagh provide no reference or data suggesting

that barefoot activity, when practical, is either "outrageous

or untenable."

We will now briefly deal with conflict of interest

guidelines. MSSE  is among a small group of medical

journals that have no published guide lines that require

authors (also editorial staff and rev iewers) to disclose

potential conflicts of interest related to work s ubmitted

for publication. Here are extracts of published guidelines

from two medical journals:

"The Journal  asks authors of research articles to

disclose at the time of submission any financial arrange,

mem they may hav with a c ompany w hose products

figure nrnmlncntlv in the submitted  manuscript, or

with a comnanv making competing products ...

 Because the es senc e of revie ws and editorials is selection

and interpretation of the literature, the Journal

 expects that authors of such articles will not have any

financial interest in a company (or its competitor) that


 makes a product discussed in the ar ticle." (Information

For Authors, The New England Journal fMedicine).

 " ... The letter should inc lude any inti rmation not

given on the title page that might be elevant to a

possible conflict of interest, e.g., consultancies stock

ownership or patent licensing arranzements." (Infor mation

For Authors, The Journal of the American

Geriatrics Society).

 Individuals with financial interest in products that

they investigate have difficulty in maintaining the detachment

required to objectively interpret data. This

conscious or unconscious bias results in commercial

advertising-not science. Scientific publications have

these guidelines to help assure reliable reporting and

interpretation of research.

 Being late at developing conflict of interest guidelines

has advantages. MSSE  can introduce up-to-date guidelines-

we believe that these standards in man journals

could use modernizing. For example, despite disclosed

financial interest in a product, authors are occasionally

allowed to publish with perhaps certain revisions to

distance themselves from these products We see nothing

improper with this other than that the reader is not

informed about it We believe that disclosed potential

conflicts of interest should be included in published

reports. The Editor-in-Chief is then freed to publish

work without later risking charges regarding authors

w ith conflicts of interest. Potential conflicts of interest

could be reported following acknowledgments.

In the case in point, Dr. Frederick was the previous

director of research for a footwear manufacturer using

the brand Nike.  He has commercial relations (consulting

and research contracts) with a number of athl etic

footwear manufacturers through Exeter Research Inc.,

 a personal corporation. Dr. Cavanagh has simila commercial

relations with athletic footwear manufacturers

using brands: Nike, Puma, Etonic,  and Avia.  It should



C. C. CAMPBEll, and R. K. SIKES. The incidence of injuries and

hazards in recreational and fitness runners (Abstract). Med. Sci.

Soares Exerc. 16: 113, 1984.

2. MARTI, B. Relationships between running injuries and running

shoes: results or a study or 5.000 participants in a Iti-km runthe

May 1994 Berne Grand-Prix etudy. In; The Shoe in Spurt.

W. rtornnzer and B. Se[!esser (Eds.). Chicago: Yearbook Medical

Publiehere, 1989, pp. 256-265.

3. MARTI, B.J. P. VADER, C. E. MINDER, and T. MELIN. On the

epidemiology of running injurie~; the Bern Grand-Prix study.

Am. 1. Sports Med. 16:285-294,1988.

4. McNITT-GMY, J. L. and T. YOKOI. The influence of surface

characteristics on the impulse characteristics of drop landinos.

rroceennas ortne mn  Annual Meeting or tne  America n S ociety

on Iliomeehanics, Auo' 23-25, 1999, BuriinEton, VT, 1989, pp.


). NIGG, B. M., A. H. BHILSON, J. DIiNOTll, S. M. LUlITm, and A.

STACOFF. Factors influencing kinetic and kinematic variables in

Official Journal of the American College of Sports Medicine 147

 be noted that these footw ear manufacture rs produce

products presumabl in part based on these consultants'

 recommendations that our res earch has shown

c re ates t he discomfort-impact illusion thus promoting

chronic overloading. These conflicts of interest, which

were not disclos ed in their letter change its meaning.

For example the ir defe nse of footw ear manufactur ers

can be v iewed as a pretext to protect their financial

position as consultants to them What makes this example

of conflict of int erest sad and cogent is that

these authors are senio researchers w ho act as role

models for y ounger inv es tigators.

Clearly Frederick and Cav anagh are not happy that

science is progressing along a path that they did not

anticipate. Their letter is littl more t han an advertisement

for the current running shoe in which they have

financial interest and for w hich the are in part answerable.

As science it is without substance because

after removing the camouflage of feig ned self- righteous

indignation, hyperbole platitudes, and jargon from

their letter there is not one refer ence (or ev en unpublished

data or personal communication) suggestin that

these footwear are safe nor do the counter  data we

present indicating the ar e dangerous.

Frederick and Cavanagh blame their displeasure on

devious misleading authors incompetent reviewers,

 blind editors and decepti ve statistics. more plausible

and ethical explanation of their discontent is their lack

of objectivity and their self-interest.

Steven E. Robbins M.D.

Gerard J. Gouw Ph.D. (eng)

Human Performance Group

Department of Mechanic al Engineering

Concordia University

running. In: Biomechanics of Running Shoes. B. M. Nigg (Ed.).

Champaign, IL: Human Kinetics Publishers, 1986, pp, 139-1 S9.

6. ROBBINS, S. E. and G. J. Gouw. Athletic footwear and chronic

overloading: a brief review. Sports Med. 9:76-115, 1990.

7. ROHIHN~S, .E. and G. J. Gouw. Modern athletic footwear: unsafe

due to perceptual illusions. Mad. Sci. Sports Exo»: 2J:217-224,


SI. Ronnnrs, S. h. and A. M. YAI'JI'JA. Running related injury prevention

through barefoot  auaptauons, Mea. sa. soons sxeic.


9. RQHIHN~,S. E., A. M. HANNA, and O. J. oovw ov enoac

protection: avoidance of'hoavy plantar surface loading. Mad. Sci.

Stxms tixerc. 20:1\)-92. 19M.

10. ROBBINS,S. E., A. M. HANNA,and G. J. Gouw. Running related

injury prevention through innate moderating hshnvior. M uti Sci.

Spons Exctc, 21;130-139. 1959.

II. ROIlIlII'JS, S. b., A. M. lIANNA, and L. JONES. Sensory attcnuauon

induced by modem athletic footwear. J. Test Eval; 16;412-416.