AD-780 665

COMPARATIVE EVALUATION OF SWIM

FINS

W. G. Fischer

Navy Experimental Diving UnitI Washington, D. C.

1 March 1957

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NAVY EXPERIMENTAL DIVING UNIT A)D 7 YWASHINGTON NAVY YARD

WASHINGTON, D.C. 20390

EVALUATION REPORT 18-57

COMPARATIVE EVALUATION OF SWIM FINS

PROJECT NS186-203 SUBTASK 9 TEST 1

W. G. FISCHER1 MARCH 1957

, [p'Z ;, fi j2 -h-1 ...JUL 2 1974

CONDUCTED

F. T. STRICYLANDGMC (DV) USN

Alwoved tLe pblio -release; distribution u11mitg",

PREPARED ____

W. G. FISCHERBMI (DV) USN

Rep-oduced bySUBMITTED: NATIONAL TECHNICAL APPROVED:

INFORMATION SERVICEU S Department of Commerce ",

Springfield VA 22151 .

E. H. LANPHIER M. DES GRANGES4 LT (C)USNReproduced frombesLT (MC)tUSN be, avwilabl, copy. CDR USN

ASST MEDICAL OFFICER OFFICER IN CHARGE

The results of these test shall not be circulated, referredto, or otherwise used for advertising purposes or for sales otherthan those leading to ultimate use of the product by any agencyof the Federal Government.

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ABSTRACT

Fourteen commercially available types of swim fins wereevaluated for efficiency and comfort with the aim of determiningwhich were the most suitable for Naval use and of learning whatfactors in design favor these characteristics. Efficiency wasstudied by measurement of oxygen consumption in stationaryswimming against a constant force in 15-minute runs. Thedifferences found in efficiency were large enough to have distinctoperational importance.f/'Systematic recording of the subject'simpressions showed large differences in comfort. Only one ofthe most efficient fins was, rated "above average" in comfort.In general, large blade area favored efficiency, and show-likeenclosure for the foot favored comfort. Observations ofswimming technique emphasized the differences between stationaryswimming and free swimming and the conclusions concerningefficiency must remain tentative until the importance of thesedifferences can be determined. Furthered study with freeswimming is recommended to this end.

SUMMARY

PROBLEM

(1) Determine which of the commercially available typesof swim fins are most suitable for Naval use from the standpointsof efficiency and comfort.

(2) Determine what factors in fin design are mostconductive to efficiency and comfort.

(3) Learn as much as possible about the relationshipsbetween fin efficiency and swimming technique.

FINDINGS

(1) Out of 14 types studied, only 3 were found to haveoutstanding efficiency according to measurements of oxygenconsumption in stationary underwater swining. Only one ofthese was rated "above average" in comfort. Two others werealso considered reasonably satisfactory in both respects.

(2) In general, the most efficient fins were those withthe largest blade area, and the most comfortable were thosewith full foot enclosure ("shoe type").

(3) Observation of swimming techniques emphasizeddifferences between free and stationary swimming. Conclusionsconcerning fin efficiency are considered tentative until theimportance of these differences be assessed.

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RECOMMENDATIONS

(1) Conduct further studies with unrestricted underwaterswimming to determine validity of stationary swimming as an ,.evaluat .on technique.

(2) If the findings of this study are validated, procureindicated fin types for naval use and continue use of stationaryswimming as simplest method for future evaluations of fin-efficiency.

ADMINISTRATIVE INFORMATION

This project was authorized by the Bureau of Ships bytelephone on January 25, 1956 and assigned project number186-203/(9) 1.

The pzcject involved using twelve men as subjects. Theactual runs required two tenders, a recorder and a supervisorin addition to the subject. A large amount of work was required

for description and various measurements of the fins and inanalysis and correlation of physical, physiological andsubjective data.

The following estimation indicates the approximate numberof man hours expended in this investigation:

DESCRIPTION MANHOURS

General preparation 36Actual runs 225Fin measurements, etc. 75Tabulation and analysis 60Report preparation 60

Total 456

The swimming runs were conducted by F. T. STRICKLAND, GMC,Descriptions and measurements of fins were made by F. T.STRICKLAND and W. G. FISCHER, BM1. Compilation of data andpreparation of the report were accomplished by W. G. FISCHER.E. H. LAMPHIER, LT. (MC), USN prepared the project outlineand provided general supervision.

Work commenced on February 23, 1956. Swimming runs werecompleted on May 2, 1956. Work was resumed (measurements,

compilation of data, preparation of report) May 3, 1956 and .,completed March 1, 1957. This report is issued in the EvaluationReport Series. It is the final report of the project.

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CONTENTS

Abstract iiSummary iAdministrative Information iiiContents ivList of Tables vk,

1. INTRODUCTION1.1 Introduction 11.2 Objective 11.3 Scope 1

2. DESCRIPTION2.1 General 22.2 Characteristic of fins 22.3 Fin materials 3

3. PROCEDURE3.1 Preliminary steps 33.2 Conduct of runs 43.3 Order of scheduling 43.4 Fin sizes 5

4. RESULTS4.1 General 54.2 Oxygen consumption 54.3 Comfort ratings 64.4 Physical measurements 74.5 Swimming techniques 7

5. DISCUSSION5.1 General 75.2 Factors influencing efficiency 75.3 Factors influencing comfort 85.4 Validity of subject's estimates of efficiency 95.5 The "ideal" fin 95.6 Questions requiring further study 10

6. CONCLUSIONS6.1 Findings 116.2 Conclusions 116.3 Recommendations 12

APPENDICESAppendix A - Tables and FiguresAppendix B - Subject's comments concerning finsAppendix C - Data FormsAppendix D - Method of measuring oxygen consumption

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REGISTER OF FINS STUDIED

Desig,.Letter Commerical Manufacturer or sourceAssigned Name

A Duck Feet ("Gaint U.D.T") Spearfisherman, HuntingtonlBeach, Cal. (1)

B Voit-Churchill (regular) W. J. Voit Rubber Cc.

Los Angeles, Cal (2) (3)

C Voit Viking

D Cressi Rondine (reg.) " " " (3)

E Duck Feet (Reg.) Cressi, Genoa, Italy (4)

F Voit-Churchill ("U.D.T.") Spearfisherman, HuntingtonBeach, Cal. (1)*1 G " " (Gaint)

H Cressi Rondine (Gigante) W. J. Voit Rubber Co., £

Los Angles, Cal. (2) (3)

I Manatee (Reg.) " " t i

J Manatee (Gaint) Cressi, Genoa, Italy (4)

K Skin Diver U.S. Divers Co., Los AngelesCal.

L Power Dive if of it it

M Aqua Matic " " " "

N Mares "Caraiba 55" ""

Mares, Rappallo, Italy

Notes:(1) Now Swimaster Division of Pacific Moulded Produce Co.

Los Angeles, Calif.(2) These types originally manufactured by Owen Churchill,

Los Angeles Calif.(3) Now a subsidiary of American Machine and Foundry Co.(4) Distr. by Healthways, Los Angeles, Calif. (Now I'

manufactured in U.S.A)(5) Distr. by the General Tire and Rubber Co. Pennsylvania

Athletic products Division, Akron, Ohio.

The information on this sheet is for Department of Defenseinformation or use only. Remove this sheet before disclosing -

or forwarding this report outside the Department of Defense.

infrmtin r seony.Reov thssee-eor iclsn

LIST OF TABLES

Table 1 - General Description of Fins

Table 2 - Fin M-:Basurements

Table 3 - Fin Size Chart

Table 4 - Data Concerning Subjects

Table 5 - Sequence of Runs

Table 6 - Base line runs

Table 7 - Oxygen Consumption Values from comparisonruns (liter per min.)

Table 8 - Subject's increase in swimming efficiency

Table 9 - Analysis of mean oxygen consumption values;

comfort ratings

Table 10 - Subject's impression of fins; general comfort

Table 11 - Subject's impression of fins; performance, etc.

Table 12 - Subject's impression of fins fit

FIGURES

1-14 Photographs of fins

15 Method of measuring fin-stiffness

16 Graph of oxygen consumption data and comfort rating

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1. INTRODUCTION

1.1 Introduction

1.1.1 Many types of swim fins are now comnericallyavailable and some of the differences between them arepronounced. Pr'liminary studies indicated that the resultingdifferences in propulsion efficiency in underwater swimming --might well be important in terms of operational effectivenessand of gas use rates in scuba diving. Differences incomfort are obviously also important. However, availableinformation offers no basis for choosing among specifictypes or for assessing the various chara.:terics of findesign. It is especially hard to evaluate actual efficiency.Subjective impressions of efficiency are likely tobe quiteunreliable as a small advantage in comfort may influencea man in favor of an efficient fin. -

1.1.2 The need for comparative evaluation of available finslead to establishment of this project. It was intended toprovide conclusive measurements of efficiency. It was alsointended to consider all factors which enter into selectionof the best types of fins for naval use.

1.2 Objectives

1.2.1 The objectives of this study were:

1. To determine by comparative evaluationthe swim fins available on the commerical marketare most suitable for naval use, consideringprimarily:

a. Efficiency in propulsion_Lb. Comfort and related factors

2. To determine, if possible, in the course ofevaluation, what factors in fin design aremost important from the standpoint ofefficiency and comfort.

3. To learn as much as possible about interrelation-ships between fin characteristics and underwaterswimming technique in regard to efficiency ofpropulsion.

1.3 Scope

fins and not a study of fin swimming technique. However,

certain additional measurements related to technique wereVobtained where practical.

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1.5.2 The comparisons were made with stationary underwaterswimming against a single force. Time did not permitconducting desired measurements during free swimming inopen water.

2. DESCRIPTION

2.1 General

2.1.1 Fourteen different makes and types of fins wereavaluated in this study. These included the fins mostcoramonhy used in the Navy, the leading ones on thecommercial market and most of the available types havingunusual features.

2.1.2 Letter designations were assigned to avoid use ofcommercial names. (The key to these names is includedin this report as material to be withheld from distributionbeyond the Department of Defense).

2.2 Characteristics of fins

2.2.1 Swim fins are devices for increasing the propulsiveforce generated by the legs and feet in swimming byproviding larger surface areas for transmission of musclarforce to the water. The reduce "propeller slip."

2.2.2 Available fins have a majority of features in common.Type provide a shoe or strap foot attachment and a bladewhich amounts to an extension of the foot beyond the toes.

2.2.3 There are two main types of foot attachments; fullshoe and heel strap:

1. The more common (heel strarprovides a foot pocketwith the heel cut away, having a heel strap. Insome models the strap is in one piece, integralwith the fin; and in other models the strap isseparate, in tow pieces, provides some adjustmentfor foot size.

2. The other type provides a full "shoe" enclosing,.he foot completely. No adjustment of size ispossible with this type.

2.2.4 The "blade" is the extension of the fin beyondthe toes, usually consisting of two ribs extending forwardwith one from either side of the foot and a web betweenthe ribs. It may have additional stiffening such as ridgesin the web itself.

2.2.5 There are several means of stiffening, with ribsbeing the most common.

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1. The ribs are thick rubber ridges that arejoined to the foot section of the fin to

help stiffen the body of the web.

2. The web is that piece of flexible moulded rubberwhich joins the rib together forming thepropulsion part of the fin.

2.3 Fin materials

2.3.1 Terms used by manufacturers to describe materialsused include:

1. Pure rubber gum 5. Hard rubber2. Gem rubber 6. Moulded rubber3. Live rubber4. Synthetic rubber

The actual significance of these terms is ill-defined.

3. PROCEDURE

3.1 Preliminary steps

3.1.1 An assortment of fins representing the major typesoffered on the commerical market were obtained.3.1.2 A code letter was assigned to each type or model

and a number '-o each pair of fins within the type ormodel. (See article 2.1.2).f 3.1.3 Measurements of size, contours, stiffness andhardness were made using the methods indicated in Figure15 and Table 2. _

3.1.4 The indicated physical measurements and relatedobservations concerning each type of fin were recordedon Data Form #2, shown in Appendix C. A separate formwas used for each type or model.

3.1.5 A top, bottom, and side view photograph was takenof each type or model. These photographs are presentedas Figures 1 through 14.

3.1.6 Each subject was assigned a "baseline" fin to beused for making his "baseline" oxygen consumption runs, K'taking into consideration, where possible, the following:

1. Experience with a particular type or model.

2. Random assignment in regards to size of mancompared to size (blade area) of fin.

3. Best possible fit from sizes available.

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3.1.7 "Baseline" runs were runs made to establish eacheach man's plateau of efficiency on a given type of fin.Three or more baseline runs were made by each subject, and

. an average of 02 consumption value derived from these runswas used for data purposes in comparisons of the fins.The assignment of baseline fins to individual subjects ',

is indicated in Table 6.

3.1.8 The order of subject-runs with the various fins isindicated in Table 5.

3.1.9 The height, weight, age and various body measurements

of the subjects were determined and recorded. (See Table 4)

3.2 Conduct of runs

3.2.1 The runs consisted of underwater swimming against -a counter-weight "trapeze rigged to exert a force of 8pounds against the swimmer. (In previously studying "trapezeswimming", an eight-pound force was found to produce thesame average oxygen consumption as open-water swimming ata speed of 0.85 kts. See EDU Formal Report 1-55 "A TrapezeSwim-Ergometer" for further details.

3.2.2 The subjects employed a closed circuit oxygenrebreathing scuba (a 1952 Lambertsen Amphibious RespiratoryUnit, Model T-4). Oxygen was supplied from a small,calibrated cylinder. The pressure drop in this cylinderprovided the basis for measurement of oxygen consumption.This procedure is describe& further in Appendix D.

3.2.3 The runs were of 15 minutes duration, and thefollc wing information was recorded periodically duringthe runs:

1. Pressure reading of supply cylinder, recordedevery minute

2. Number of kicks per minute3. Kick width4. Degree of knee bending.5. Fin flexion6. Consistency of style7. Unusual features, if any

3.2.4 A graph of cylinder pressure versus time was madefor each run (Appendix D). K.3.2.5 Each subject made one comparison run on each typeof fin and recorded his impression and findings as tocomfort, etc., on the subjects impression form, DataForm #4 (Appendix C). These impressions wiere latercompi±eu on a single form for each type of fin.

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3.3.5 At the conclusion of the regular evaluation runs,each subject made an additional run on fin types A & Bto obtain an indication of the amount of improvement inswimming technique which might have occurred since A,B, C, & D were originally studied.

3.4 Fin sizes

3.4.1 In general, only one foot-size of each fin-type wasavailable for study (what these sizes were is shown inTable 3), and in several cases only one size is manufactured.Except in two cases (C and E) the size was "large".in a few cases, the fit was so poor that a subject wasunable to make a run with a given fin. Where the finwas simply too large, subjects often wore foam neoprene"boot sox" to improve the fit. This was a reasonablysatisfactory arrangement in many cases.

4. RESULTS

4.1 General

4.1.1 Information concerning the various types of finis presented in Tables 1 to 3. Table 4 contains height,weight and various body measurements of the subjects.The oxygen consumption values are presented in Tables 6to 8. Tables 10 to 12 summarize the subject's irpressionsof the fins, and specific comments are presented inAppendix B. Oxygen consumption values and comfortratings are tabulated together in Table 9 and presentedgraphical in Figure 16.

4.2 Oxygen consumption

4.2.1 The ave,;age oxygen consumption for all subjects t' *using all fins was 1.30 liter per minute, and the rangeof means for individual fins was from 1.13 to 1.46 litersper minute. The lowest mean oxygen consumption values,indicating the greatest efficiency of propulsion inthe kind of swimming involved, were obtained with typesM, C, and A in that order. The highest values, indicatingthe least efficiency, were obtained with types F, B, Gand N.

4.2.2 Comparison of the initial and final runs with typesA and B indicated an improvement (reduction in oxygen

- consumption) of 14% and 16% respectively.

4.2.3 Examination of "baseline" data (Table 6) showsdistinct improvement in the performance of some subjectsmaking repeated runs using a given fin, but there isconsiderable irregularity in the baseline results as awhole. Table 9 indicates that the mean of baseline valuesused for data purposes is 1.26 liter/min. compared to the

*51 overall mean of 1.30 liters/min.

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4.3 Comfort ratings

4.3.1 Examination of Table 10 and Figure 16 indicatesthat the fins which received the highest overall comfortratings were types HI JP and D. Types C, F, and G werealso above average. All fins of the "shoe' type wererated "average" or above. The fins most distinctlybelow average in respect to comfort were B, M, and K.

4.3.2 Note that 2 of the 3 most efficient fins, types4A & M, were below average in comfort and that some which

were below average in efficiency rated high in comfort.In the case of fins A & M, examination of the tabulatedsubjective impressions (Table 10) indicates that one ofthe main complaints was that the fins slipped, slid or hada tendency to turn on the foot while swimming.

4.3.3 Examination of Table 10 also indicates that inmany cases (never in more than half of the runs concerned,however) discomfort was attributed to poor fit. Thiswas particularly true in the case of types C, E, and I.(C and E had the smallest foot-sizes of the fins used.)in ceneral, the most frequ-at specific complaints wereCorcerned with "slipping or sliding" and "rotating onthe foot" and with "pressing on bones" and "cramped toes".The -crmer complaints were most frequent with largefoot-size fins, the latter with the smaller ones. Inalmost all types (See Table 12), the majority indicatedthat they considered fit satisfactory. Type A yieldedthe most "too large" comments. The "medium large" fins(C and E) were considered too small by 4 individuals. Onewas unable to use C at all, and another could not uje K.Only one "extra large" fin was considered too small byany subject. In three cases, the boot sox were wornby a majority of the subjects (with fins A, B and H).

4.3.4 Subject's impressions of swimming ease (Table 11)showed a considerable proportior of "easier" commentswith types E, H, J and M. A ma:,ority consideredswimming harder than usual wit! A, B, K, and N. Unusualfatigue was reported more frequently with th B typesthan with the others, as was a necessity for alteringtechnique in order to get the most out of the fins.

The types which the majority of subjects indicated theywould be "satisfied to continue using" were C, D, E, HM (those ranking highest in efficinecy), a cross-section

of the subjects expressed the opinion that these typeswere too large for sustained swimming from the stand-pointof endurance. Unusual difficulty in walking when wearingthe fins was reported most frequently with types A, C, D,H and M.

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4.4 Physical measurements

4.4.1 Blade area values, as recorded in table 2, indicatethat the types having the greatest area were M, J, A, C,G and H in that order. Types B, F, K and N had thesmallest blades.

4.4.2 Among the fins showing larger blade areas, the dataconcerning stiffness indicates that only G was markedlybelow average in this respect. The photographs, figures 1to 14, show that this fin lacks the ribbing characteristicsof most of the other; and the durometer readings show that

V this fin was also relatively low in "hardness" of itsrubber.

4.4.3 The highest durometer readings were obtained from -types H, Liand D. The lowest were obtained from A, B andJ. Only L, N and C indicated much difference betweenthe hardness of rubber used in the foot attachment andthe blade, with the blade being the hardest.

4.4.4 Types which had positive buoyancy (which floatedI

in water) were A, B, C, E, and F. 'he rest ranged fromneutral to 0.5 pounds negative.

4.5 Swimming techniques

4.5.1 In almost all cases, the wimming technique employedby the subjects included a slow rate, (average about 18cycles per minute), and a wide kick ranging from 30 to 44inches, heel to heel, with considerable bending ofthe hneec. (Tabulation of this information in detail wasnot considered worthwhile.)

5. DISCUSSION

5.1 General

5.1.1 As Zigure 16 shows, the oxygen consumpt-ion datapermits considerable differentiation of the various finsstudied as to their efficiency for the kind of swimmingemployed in these tests.

.5.1.2 The fact that one group of fins was studiedseparately at the beginning of the project, (Types A,B,C,D) "

and that the general efficiency of the subjects improvedconsiderably during the course of study, it is not likelyto have made any important difference in the relativestanding of the types tested. The averages of the earlyand late values for types A and B were used as their meanvalues in the graph. The average improvement (Table 8)was 15%, so the mean values for types C and D wouldprobably have been only 7 to 8% lower if later runs had

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been made and the data computed in the same way. Type Cis already distinctly above average in efficiency. TypeD would probably have remained in the "average" or "belowaverage" group. However, it is clear that the "learningfactor" is large enough to be a potential source ofconsiderable error in fin evaluation.

5.1.3 In general "practice" on the part of the subject(as seen in the baseline data, Table 6 and 9) maderelatively little difference in the apparent efficiencyof a fin. The overall difference in oxygen consumptionbetween the "baseline runs" and the general comparisonruns is so small that extensive practice with a fin beingstudied could not usually be justified in future evaluationsof this type.

5.1.4 The difference in mean oxygen consumption with thevarious fins seem relatively small in these tests. However,if it is valid to consider these differences in terms ofsustained free swimming, they represent a sizeable operationaladvantage with a more efficent fin. Calculation based ondata from EDU Formal Report 14-54 (Oxygen Consumption inUnderwater Swimming) indicates that a man using the type Mfin, which had the lowest mean 02 consumption of all types,could swim approximate 30% farther at normal speed with agiven air or oxygen supply than he could with type F, whichhad the highest mean oxygen consumption. In terms of speed,a man could swim approximately 20% faster (without increasinghis effort or using any more air or oxygen) by using thetype M fin instead of the type F.

.2 Factors influencing efficiency

5.2.1 The findings of these teats shows a positiverelationship between blade size and efficiency. The finswith the largest blade also showed the greater efficiencyprovided that the stiffening was sufficient for the size.There were only tow instances in the evaluation where highefficiency and a large blade did not go hand in hand. One,(Type G) was a fin that was above average in blade sizebut with very little stiffening. This type yielded thesecond highest mean oxygen consumption of all types. Inthe other instance (Type E), the fin had a slightly smaller .than average blade but had good stiffening and yielded thethe fourth lowest oxygen consumption.

5.3 Factors influencing comfort

5.3.1 Poor fit was clearly an important factor in thediscomfort reported with several of the types. Except inthe few cases (only H and J) according to table 3 inwhich no other size was manufactured, failure to obtain al:duse a proper range of sizes was a serious defect in the study.

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The comfort data must be interpreted cautiously for thisreason. Use of the foam neoprene boot socks with "too large"fins probably reduced thp number of complaints materially,especially with fins like A, B and H.

5.3.2 The general acceptance of the "shoe" types, despiteproblems of size, indicates that arrangement favors comfort.

5.4 Validity of subjects estimates of efficiency

5.4.1 Until the present work, about the only index of theefficiency of a fin has been the user's opinion. Thisstudy afforded an opportunity for comparing opinions withan objective measurement. The subject' estimates of easeclassified the fins as having above or below averageefficiency almost as well as did the oxygen consumptiondata. Only in the case of type A was marked divergencenoted.

5.4.2 In this connection, however, note that stationaryswimming on the "trapeze" requires the subject to producea specific force by his efforts throughout the run. Hemust accomplish a definite amount of external work, andit should not be unduly difficult for him to tell whetherone type of fin requires more effort in the process thananother. In unrestricted swimming in open water, thiswould not be the case, unless the swimmer had a constantindication of his speed, his opinion would probably bemuch less reliable.

5.5 The "Ideal" fin

5.5.1 To have the best suitabiliry for naval use, a swimfin must obviously be as efficient and as comfortable aspossible. Although this study shows that these qualities - 'are not found together in many available types, they shouldnot be incompatible.

5.5.2 The results indicate that optimum efficiency can be• expected from a fin with a Large, well stiffened blade. The

fin with the largest blade area (Type M) was the mostefficient, so the study gives no indication of whar the upnerlimit of desirable blade area may be. The limit might beimposed by the cumbersome nature of a large fin rather thanby a drop in efficiency with increasing size. It is alsopossible that free swimming would show less advantage in

.large blade area than was noted in this study (See 5.6.1).In addition the fact that many of the subjects expressedthe opinion that the larger fin would cause excessivefatigue on a long swim may indicate another limiting factor.This study does not indicate the optimum shape or curvatureof the blade, and these factors may be quite important,especially in free swimming. The relatively good performanceof types E and H which had smaller than average blade area,suggest that good design can yield a reasonably efficientfin even if a large blade proves impractical for some reason.

(For example, the unusual difficulty of walking was ratedw hile wearing all of the large blade fins might be a seriousdrawback in some operations).

5.5.3 If both comfort and efficiency could not be provided,comfort might be considered more vital. The importance ofproviding an adequate range of foot-sizes is emphasized bythe influence of fit on comfort and the generally poorcomfort rating of fins with adjustable straps. Proper designof the foot pocket (and strap, if one is used) is evidentlycrucial even though detailed specifications are one readilyinferred from the data. As was pointed out, a largeproportion of fins with the shoe type arrangement obtaineda high comfort rating than did those with heel straps.Reports from the field indicate that fins of the shoes typetend to come off in operations such as high-speed pickups ofswimmers by small boats, but correction of this defect -should not be difficult. Provision of a strap or lanyaredaround the ankle to prevent loss of the fin has been suggested.One of the basic types (represented by D and H) is nowprovided with an "instep lock strap". Positive buoyancy isalso a desirable feature in this connection, since it favorsrecovery of a lost fin,

5.5.4 Among the fins tested, only type C showed outstandingefficiency as well as above-average comfort. Types J and Hcombine high comfort rating with above-average efficiency.

Types M and A showed high efficiency, but they were belowaverage in comfort. Without knowing how much "relativeweight" to give comfort and efficiency ratings, it isdifficult to rank the various types in order of "overallmerit". Fins which ranked below average in either respectprobably need not be considered for procurement. However,several types which are already efficient could probablybe made acceptable by relatively small changes in designto improve comfort. Simply using proper foot sizes wouldhelp considerably in some cases.

5.6 Questions requiring further study

5.6.1 The fact that this study had to be restricted inseveral ways leaves a number of important questionsincompletely answered. Most of these concern the apparentdesirability of large blade area.

L5.6.2 One factor that could not be evaluated in thesetests was "fin drag" (the drag created by the fins trailingin the water in free swimming). This would have to betested by "free swimming" runs and might vary with theindividual kick style of the subjects employed. The kickstyle used in trapeze swimming is almost certainly different -from that used in free swimming. The width of kick used intrapeze swimming varied from about 30 to 44 inches, dependingon the size of the individual. In free swimming it would

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probably be considerably shorter, possibly as much asone-third less. These observations may be particularlysignificant in view of the obvious fact that movement-through-water is minimal in "trapeze" swimming.

5.6.3 It is also possible that the most efficient fins 3in these tests would tire a man too quickly in sustainedswimming unless he was highly experienced and his leg -muscles were well conditioned (See articles 4.3.4 and 5.5.2).

6. CONCLUSIONS

6.1 Findings

6.1.1 Measurement of oxygen consumption in stationaryswimming against a given force showed distinct differencesin the propulsive efficiency of various fins (article 5.1.1). -

6.1.2 Improvement in the subjects' swimming efficiency

during the course of the study caused the mean oxygenconsumption to decrease about 15%. (article 5.1.2).

6.1.3 The comfort of swim fins, as indicated by thestandarized rating by users, varied widely amoung thevarious types (Section 5.3, Figure (6)).

6.1.4 With few exceptions, the fins with the largest bladearea showed the greatest efficiency (Article 5.2.1).

6.1.5 Fins with the shoe type foot socket received thegreatest proportion of high comfort ratings (Article 5.3.2).

6.1.6 Relatively few fins ranked high in both comfort andefficiency. Only type C had both outstanding efficiencyand an above-average comfort rating. Types J and H combinedgood comfort ratings with above-average efficiency -

(Article 5.5.4, Figure 16).

6.1.7 Observations of kick 7r-ate and other aspects ofswimming technique indicate? definite differences between"Trapeze" and free swimming in addition to the obviousabsence of "movement through the water" in the former(Article 5.6.2).

6.2 Conclusions

6.2.1 The observations of this studywarrant the following

conclusions in terms of methods employed. F1. Measurement of oxygen consumption in the standarized

form of swimming provides a satisfactory means wt.of determining ths relative efficiency of differenttypes of fins (Article 5.1.1).

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2. Improvement of subjects' swimming ability duringthe course of study is a potential source of errorin applying this method of evaluation, but it didnot seriously effect the results of this study(Article 5.1.2). '0

3. Large blade area (assuming adequate stiffening) r'."favors optimum efficiency (Article 5.2.1).

4. A "shoe" type foot socket is most conducive tocomfort (Article 5.3.2). (Measures to preventthis type of fin from coming off in certainoperational situations may be required.)(Article 5.5.3).

5. Giving efficiency somewhat more "weight" thancomfort, the type C fin is considered the bestof commercially available types for general navaluse. Types H and J should also be suitable(Article 5.5.4).

6.2.2 These conclusions, e3pec:ally 3 and 5, must beconsidered tentative in vie , of the limitations of thisstudy. The importance of the differences between trapezeswimming and fcee swimming in this connection has notbeen evaluated (Article 5.6.2), and the influence of longeruse and fatigue on efficiency and comfort was not investigated(Article 5.5.2 and 5.6.3).

6.3 Recommendations

6.3.1 The primary recommendation concerns further work todetermine the validity of the results of the present study .(Section 5.6). The basic requirement is for a limitedseries of free swimming runs conducted along the followinglines:

1. Include not only the most promising fin types inthis study (i.e. C, H and J) but also a sufficientcross sec-tion of the other types to permit adequatecomparisons. Omit those obviously poor from thestandpoint of comfort; assure use of properfuot size wherever possible.

2. Conduct runs at a range of controlled speeds(i.e. 0.7, 0.85, and 1.0 knots).

3. Insure that at lvast some of the runs are ofsufficient length to determine the effect oflonger use and fatigue on efficiency and comfort.(Article 5.6.3).

4. Arrange assignment of fins and scheduling of subjects'

runs to minimize "learning" effects (Article

5.1.2).12

PPw

5. Secure "operational"' tests which will demonstrateany possible defects such as the tendency for agiven type to come off during swimming pickup.(Article 5.5.3).

6.3.2 If the results of the present study are validated,the following recommendations are considered warranted: -

1. For procurement of fins for naval use, let typeC be the first choice. If alternative typesare required, consider types J and H. If themanufacturers of types A and M will take indicatedsteps for improvement of comfort of these types,consider these fins for further evaluation andpossible procurement (Section 5.5).

2. Consider developmental study to investigatemaximum practical efficiency thiough large bladearea, optimum shape and curvature, etc. Concentrate

N on shoe-type foot socket in developmental models.

3. Continue use of trapeze swimming siudies assimplest procedure for evaluation of comfortand efficiency of fins.

3 ,

li,:,13

TI,

(see notes)

IA

04 m -1

*) let (.1)'I E'e p 3~ rib 3.2 Co"

CaV-Al bro.; g u j B. st-rp 3 ribs 10cov.

~ave ora sie2rb !6 a. 0

aI r si I- I' F,- . 1lg. be rucidr' so 2 ribs, IO "Lat. c0v. 9!lag av. c., ik s.? sho 2 ribs 200 cone,, 170

large VIM~T ur u~ strap 3 r-,bs 72 com,, 00

av. bluo' molde 2rp.1x 26.s al 0 2t. 0 -

* large greea p.v r ib i8~m.

av. a"k bro' - n-t Iui oiap 3 yi' 0 1'ov 0 10 I'

in lrg Fw euu strp 2 ris. 70 ov, 00c 0

riv. e 15 m 10 oldd "I a3' 3. srna. 0 r I 0? 0strwtp Iisl~oI~

large , eord 2f filles 120y-ln anl0 0 ei01t,

(2 FinWcd. anjo,!.do 3-, evnio duu) InI 10) NNLI-r i al.to'Ev

'(S~t oOA

-. 4-

() M 5nC' - r jq '0 hia0

2 8- R - 331 I - 10o8 3- - .5

* 20X' - 9.0- 2.5 rL52 - 11.0 2.8 + 4,,! Oo .1 6o -18.03- 7* 2-3 015 n 1.1 3-0 -oa. 58 70 7 5

17,5- P.0 - 2.90 91 - 1000 3.0 + 43 113 4 ,o

15).,8 8.8- 3. J, 83 -).l-.6 3 toll + i5 60 3-,0-

P_0_'O_.1~~~~ 9. 8*:5--O118 ,,.0 h -4

20A, B8.1. M2 10 11 ,9 3.1 -0.3 )17 O8 i.o iI,. -8- 9~ 3. 105. - 10,.h 28 0 53 53 I i

!.5 7.9- 2.0 e.-5 9-5 3.3 -0.,! 68 69 4.5 -

18.0 - 7. 0 9 100 2 O 0 7 "'.J - 6

"- 8 .12 2. 3 1), 11O 3.0 -00:1 50 613 6.0

rarii initf Ual apeors to* b only sizo ynado.

v sh ivilicates Fn ha adui:v.otable rs

g'~ivel trn w'dight (in pouncls) rnolaiirad to lymdl fin (>.u ta3 i-,Icc r lon

_/S /

sizes sa~ cid -U*o be rn.anuact-ured,,

j -. ,,har f- . -. . .

.Tye In 7ng Ic

F X VI** 41

I ) 8-9

1 ~9.41 ? j:

4,43 8-.13*

L

9-13"

_____ - ______ m7At efo i'Ald',Im a

- used illn hi s stj3y* .

, 1) 9.1 0 .e.:C3 0 4' 7J' 0- 0- %3 1

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p. H al :) o"

I~ *\. tom)4Mc - Co ~

V-1 11 ..

W COC l Q -kl IC-01

IA ~ \ 0A IA r4I A '. . .~I

I.. ___________________________ _______________co_

) IW-Kvi ~ i

0\ t Nr4I

C.)~

4 P o

IE-VI %M U CM 11"-

It, 0 ! Ci4 CV-i

CA' Ca C Cvj (M~ -- CV%)

- E-L. CVIC' - ~ .- ~ 1-~ *~ --- I

jjC 1 ~0 1. NC3 CC! l ! CJ tl

- ' I .ta - i - ' I... "- -l

-A ~ IC)cV A~

1A W .- If1 a(\ V\fl C, I .-

r-1 H. I\ \0' CVC. H %10

r\ CV eO '.\I C4 IT0 C ' IN'0 (1

N ~ Cr. m'Ir InH

*- . - -...-. i*..-. IS\ 1v J a2

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* .CV C\,a - 1 1

ca-I

_ I.- a-

a.~. aa I J

,M - 4

ri !

I.. A:d'-€N "..--

IL

15 -- -K : 1-- - 2. -K-5

. 7 1- o L 5 .(1 1.° 4 " , 1 7°. 1o 25 .I7 ", ., 1Q : I.,a oLAI ... holL.5o.*

. 27 12 j2.?12- f .-29 . 4-16, 1-W3 L-23 I : 4-17 l~ b .23 I .... .. ."I .l~ .. .l .0L~ ". ,)" 15" l 0 Z""z

1.23 10,17 1.:52 1,48 2.4132 1.73 1,26 1-45 1,,09 1A lef

2-29 2-.28 2-~29 2-? 5-3 4-r,7 t-25 4-24 4-16 5-2 4*'44 E73 .ho 1.08 10.,o 1.31I 1.32 13511.76 1,32 1e.02 110 1 ±9 111,.6

4-1h2-28 [i-2 161__5 M916

______ j_2J. ' 0

18 1.66 1 33 1031l

4-9 -234

.9I1

1L3 ..5, t I, *:,...le used 1010 IAi0 1,23 1o13 1,,29 1.21,66 1.31 1.16 1.1.6 I,.!,6 1ol.2 .,

I 's

4J,

_________ ,- __________

c ~ j ;0 0 Cr% .7io - o C

-G C-1 co %700 In .3 Ct .

eAI.j i t V -- : % -7 ..

W P4 H %-*EH CC) co cm IA7 0 v

*C, CO %* s-, -

In %0 cm v-I s- H H HI- .C'I(6 0 03 0 ) 0 ~ 0 -

4.1

Qr 0 0% ('h 0'0 ' C

P - r4 8 1.o, C, 00 Z C"

A 0:-\) . I co 0 u

000

-I H4 1- H -I Hq C- H H

t4 0 N IA.

0 a CJ C3

b .% C'.Sj LI O %

1C. co G% 0 5 c 0

1c 0\ C L ' sI 0. 'Z rI 0 $- '1 %j% 0y 0A f 0: V

'c~ .~ HH ,- H L~j HH H HA*1j I* -4 H . -

I... M 053 r~l 1 H C,

CiC.'I.H r

IA *i\ c

~H c L..I

1h$.n Runs Co.rprimn of 1st 2nd I'mI A" 8: "1

i . FAl

SUJECT I' 1 2 1 1 22 A

ts

M" ...'I,, 1.19 .85 1.1* 1..03 1.,0.2 1.. 0* ,

ll0LTMNGM-,!M ]..!,Orr .82 1.32 A8 I.10* 1.O8

M WEIR ~ 1J.12 .93 2.02 1 .2.9 1.17 1.63

JTSN1.28 1 .16 1.79 1.59 1.22 1.69

CAPTAIN 1.5 .93 1.57 1.20 1.22 1.38 ,

ADAMS .1d.9 1.15 1.63 1.35 1.32 1.49I

KOHL I.iO 1-0.5 1.75 -o.4 -5 ____ 1.60 B

I'Ga 1.IO 1.26 1.51 1,,22 1-33 1-36

ITILIO U0T 11o01 1.25 1.o2 1.39 o13 i..6

HAa,5 1°1 .t1 1.63. 1. 63 1.20 1 .6,,.

i ___Av - % - - -. rI

.' ': , .... Z i''

I I

.''

I>

Am4ri of man C:tygoiiConsn.'tion vallus; ComforC1. rtings

In Type Flean 02 cons* ______,z n_____ 02_cons._el_+__I I '1.

A 1,17 j 1 1010 --1L5.-

B i1.L-o +7-7 1.10 116)I

C1.16 -10 .8 1.13 *-13ol 21 ,

132 1.1.23 27 "s ~E 1.22 -. c, 1.16 -1c.8 20

G 1ho - .77 1.66 +27-,7 23

H1-27 -231.29 -'O,8 28 ~

1 128 :1>1031 2L, jJ1022 ..5.2 1l.a3 2 ~

K 1-37 +5. [1

L__ :o3 +5- ___56 __20 2? L

Oralijj 1-30 I 1asohio 1h.26 I 1 22Mean IiI________ _______

I. 1U-F ,:: w ' ' " . ..... . ,

. (r,Thrber of maojects cb.cUing itowi conmemr.6 i;h D:: ,-Yom-..

Unumml fatfigua 0"ease" M

It -- J

*0 C

' n,-! -

M: 4 t )..u .

. "1 I 4 ,.* • t - ' j3?I (0 1 C, -)I U

•0 L214 0 16 7 9 7 6 6 6 9 j

14* 3 2 9i 1. 3. 2 2 14 18a

143 2 2 2 1 8

14 6 3 5 3 0 23 2 9n 1 3 7 4 3 2 3 3 :t

13125 63 2 0 0 0' 2 j6

1, 7 3 6 4 2 1 1 2 2 .1 9

14 2 14 81 1 2 0 4 .3 6 51. 6 2 4 2 1 2 . 3 7 8

1Z 2 0 3 3 4 55 4 3 3 4 a 1.,1

*I 16 1 8 7 5 5 14 Is 6 5 1 514 6 2 6 3 2 3 . 2 3 6 12

5---_ 1 ~ 4 4 51,

of .4. 'A

ir

* i?$

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Reproduced from

[best available copy.

!b . .... 2 "-

0 0114 -F ofr .ati. Spcii cot .. t

ill 0 J30 0-A° 0 Co AO F

a, 0 0c , Il It .! .

C, 0 M o ) 0 a144't 4~ Q W 1 0 P .

o o .

C) t - .,; 0 o,.0) .C0

XX 0 4" 32 0 5"- 0 p.2

L 3 8 10 1 2 16 2 r 1 017 0 7L 2NLI1 51 !z 1 2 0 - - -.

t L6 3 3 0 27 1 0 2 2 2 0 I 2,

112 5 4 1 2 20 i 3 3a 1 6 2 1i&7 1

TL2 7 1 0 1 23 1 0 1 0 02 3 1t 0 2-XL 1" 4 3 2 1 0 0 0 4 4 1 4 3

0LI 9o 1 28 . 1 0 0 0 6 3 3 1 15

[5 3 3 1 1 27j 0 2 0 1 i :i. -4 V1

. ... .... ...

LT0tl t!k 71 3. 18 17 2 27 27 13 1lI 31 1 01s9 1 2 12

I Lellen 2 Po. VPoo(3 1 for flrn, 0 3 o. "po1 5 3 3 "cas o hor the number of rus vag other "0an fI score u r

! 'I ~r. ocl,,y ,tcing mos3t. 'i,. on i,0pr&:oion of. "in m 51b .,tn;" .,,Ui: ,'

T --- 7 T 2m

SA114TJECrS' fl-f SIffil OF FI3S t'Xi

- IL

(57

A) a

L 15 c5 2.,C16

XL ____ 5 0 - 1

L 1 6

.0 2

PICTURE I FN

4 P~~OOT SIZ SICZNjwITYPE A_3 LARGE

.4.4

AFI.IFIU -

r

1,14R~ X -S16-0/0

I ALI SWIM FINSflit TURE

- * I COT SIZE SHOWN

TYI-E 13-2 LARGE

2 Aug. I95

FIG 2 FIN 5-2

RIGH vRIDE~OLrT TOP

PROJECT INS 186-203/g01CVALOF SWIM FINS

• PICTURE 3FOOT SIZE SHOWP

rYfE I.CDIM LARGE•c . I 2Aug.W6 t

A)--

I

MEDIAL EDGE

I C"

I , , * •

°

FIG. 3 FIN C-I

I LErT TOP ~ ArIG&T tC.V(RS"

I PROJECT NS 186-203/MWI EVA. OF SWIM FINS

PICTURE 4 IIFOOT SIZE 90OW.

aTYPE LARGE

2AI 1956

1 S4

-SeW. _,W

FIG.4 FIN D-1 CIi

T44

II LUT~o , -4Ti(5

".-.• LEFT Top RIG t*"RJ )D

" [~VAt. OF SWIM FINS

'II

b .0: FOOT SIZE .:3.4OWN,

•.--:;'; rs . 2AY.. r .

. .. ..

-.. ,$..-.,.:-

FIG. 5 FIN E-1

I$

RIGH UNOESI

FTIE SHOWN.R

2Auq.1956

Vv.

- ~6 'I

FIG 6 FIN F-I

1 I .

L~rT TOP - ~"

; I PROJ CT hS Ilb IU .1vj

EVAL OF SWIM FiNSP9CTUPE 70 FOO T SIZE SHOvjN

TYPE G3-1 EXTRA LAPrE

2ZAug. 1956

f 4' "* i , c". i .,

. , . . • •

" I I

!A

.

I 7 FIN G-' , : ' A.

. -. E, A.

"'. -" " . ,'

!2.

I

3? ' j* I 7 FN,-

4> ,.

|

K.'

,' . .

IIwo

-. IPR~OJECT tl61I.. 'Uw

* I.,EVAL OF SMiM FI4Sk'CTURE b

TVY'E EXTRAI.LARGE

*H- 2Au 1956

el .. ....

4, ,

IIr

1v I

L iL4

~ ;,~FIG 8 FIN H-

I IN

PROJECT NS 186-203911EVAL.OF SWIM FINS

0 FOOT SIZE SHOWN. LARGE

2 Aug. 1956

. Id

7FIG 9 F IN I-

PITR 10

44

.4'.r

-A

m',*iI

-,

40 .3.

ov,.w

FIG loFN -

.IE

V, CE TOP. iRIG-T UNDERSIDE

EVAL. OF SWIM FINS

2 Aug. 1956

FIG 11 IN K-

*~ 34

LEFT TOP ~.

FOOT SIZE S*14p

TYPE L-I LR2AYq 1956

rr

EVA C S~i 51C)WN

ITYPEm- It ARCr(

-~ 2Auq 1J56

-*2*

I,~v. , ..gig-,-

'r -. ;

FIG. 13 FIN M-

LEFT TO s L"SD

- .1 195

41' o

FI 14 FI

r "

4' ' .

.,..-. -. -,. I ', -

..4... f- 7 , I ./ "'

"- z-- N 7 ., .,; :/-- " " y]-* -.. ' I

,, *. ,4"' i

j ;. *1,.

.4.1

i f:; all- \ " '-.. .

- .\"- .

:

* ,--- . - ***~ - --

L _ _ _ _ - K

0 . - . ' a I ; S

.," , \ - 'o - ,

r4 -4

iLF

.vw.J.~Ok a~:04

____ ___

lot log - - 10

C.n

T4 t

0 C

EF ~ 0 0

31LfI M13d S3MI11 NOILfL&MNOD ZO

APPENDIYB

SUBJECTS COMMENTS CONCERNING FINS

Note: This represents a summary of the relevant statementsobtained on Data forms No. 4 in response to question#15. ("If you wish, use other side to say in yourowm words what was good or bad abour _±a i tin, offersuggestions, etc.")

FIN A. 1. Make foot size smaller, but leave blade same size.2. For fleet use the boot socks would invainably

get lost, and the fin is just too large forgood performance.

FIN B. 1. These fins had a very bad drag on my up-strokeand I had to put a lot of power in the down-stroke to keep up with the 8-pound force.

FIN C. 1. Fin was generally good, but size was too small.2. This fin. had a tendency to wobble through the

water. This is probably due to size.

FIN D. 1. (No comments)

FIN E. 1. Need larger foot size. r

2. Very good fin. ' -'

FIN F. 1. Not quite enough power.

FIN G. 1. Nothing good about this fin.2. Rubber in blade too soft for size of fin.

FIN H. 1. Fins too heavy.2. Learned more about kick style and std. kick.3. Foot size should be smiller.

FIN I. 1. Too small.2. Good fin in performance.

FIN J. 1. Fin's are good for power.2. Good fins.3. Decreased the amplitude of my kick because

apparently I have been working againstthe inertia of the trapeze.

4. This fin is much too large and cumbersome.It seemed like most of my work went intoreturning the fin to kick position. Couldnot keep a constant kick rate.

* 8 of 12 subjects used foam neoprene "boot sox" withthis fin

APPENDIX B

\-

FIN J. 5. This fin was excellent in fit, comfort and power.6. This fin is an excellent fin if you could get

different foot sizes and keep the same web. V" -

FIN K. 1. Good fit.2. Too small in area.3. Had to work too hard.4. This fin seems inefficient in the water - "slips".5. Heel strap broke when putting it on.6. Didn't seem to be getting any power.

FIN L. 1. Too small. -.

2. "Wobbled" in water.3. Fin web too small-no power.4. There did not seem to be any position or kick

style suitable for swimming with these fins.5. No power from kick.

FIN M. 1. Heel piece not adequate-needs improvement.2. Heel would not stay in place.3. Heel piece came off.4. Good power-not enough comfort to say they are

good for swimming.5. Would be better with full heel or (regular)

heel strap.

FIN N. 1. Had to work too hard-no power.2. Fins seemed to "slip".3. Buckle came off heel strap fitting-need better

heel arrangement. *4. Shoe design would be better. *

• Full shoe is provided in this make, but it was not studied.

I.

2

1.

4(3-

/

ASTWIM-FIN EVALUATION (PROJECT S186-203/9(l)

DATA-FOR14 NO. 2: PjfYSICAL CHARACTERISTICS OF FINS

1. Designator letter 2. Name

3. Model 4. Acquired

5. Manufacturer ...... .. ......

. 6. Sizes made

7. Sires under - 8. General Description:study -,;:Designator a. Size

S numbers.

Shoe size - be Color

co Type of rubber ..... _d. Stiffening .

e. 'Distinguishing features

to P~, it

9. Specific Measurementst

' ~~~a. Linear measurements SZ:, ,

1 I) Width of footspace -.- -

2) Length of footspace - -

3) Length of fin

4) Width at widest point

5) Maximum thickness

be Surface area sq. n. --

c. Weight d. Ourvature: degrees of in diam.* circle. -

1) Airlb. oz•

2) Water

lb. o.

3) Buoyancy

" Neutral

i~- (,l ____________

KI

e. Angles _________

1) Plantar or dorsal

offset______

2) Angles at end ofL

fin_______

3) Medial or lateral )(9e2,)

10. Stiffness Index

Designator letter NO* Size -of fin used.

,If~Nt Hol . 11 il

CL,~ I~~~~~~~~~~~~ 11,tiiilli Mihp ______________________________

12.Cndiio att en of std 1__

POND

1LMshp

(.i11 In b1ln;vz;, cronu ( -;r,s not CA-~~

F111 USED:()

SIZE

1 . Size 1,&Cd 2'. 8Stifctor? .. If~ 1±0.. or6 (3.Iag'i, sr;--2.r)

c iz 0? It. 1~~b,-~

~~'. ~ ~ 6(. If xb il goodl Vm. ~ l ~~~~OC '';

7~. G'M om 1po; !r S.:ro or :JI d

Ver .co 01'ol

Ankles__ Co~t. 0

10. Pled t,(o a inr~u ,I ..:ty-3.C 1-o f.t Ir :. ~n 1. vallding inl tihacs, H, wa (dirWlt, ri.. ca y

* OVM~ALT,_IF13131MT

12. ro:M.rard to A 1this Rlztter (A ha2it -Infin P.hrut sar.,ist Wor.:-a B Zin =;uJ*.v 1131-4

11.Satizi-ioc to usWi 5.1c. froz n,,cc c.;3

or lv(1 a1bot th-lu Ma.. O.Mv ,11 ~I~

~~46

APPENDIX D

METHOD OF MEASURING OXYGTN CONSUMPTION

Note: Time does not permit description of this method in completedetail. It is basically the same as that used instudies reported in E.D.U. FORMAL REPORT 14-54,Oxygen Consumption in Underwater Swimming andE.D.U. FORMAL REPORT 1-55, A Trapeze Swim-Ergometer. '

The salient features of the method as used in this study -

are as follows:

BASIC PRINCIPLE

The subject uses a closed circuit oxygen rebreathingscuba. As the subject consume oxygen, more must be addedto the system. The volume added is essentially equal to thevolume consumed (the subject's oxygen consumption).

The oxygen is supplied from a small, calibrated "runcylinder" which is equipped with an accurate gage. Thepressure-drop in the cylinder is directly proprotional tothe volume of oxygen supplied. The pressure is recordedperiodically. The pressure drop is translated into volumeby multiplying it by the calibration factor for the cylinder(volume releaced per unit of pressure-drop). Application ofcorrection factors yields the value for volume correctedto standard conditions.

APPARATUS

The Lambertsen T-4 oxygen scuba was employed. Thefacemask was replaced with a mouthpiece to reduce the

likelihood of leaks. The demand valve which automaticallysupplies oxygen when the breathing bag flattens on .inspiration was left intact. The normal oxygen Lupplycylinder and regulator were placed with a hose to asupply manifold outside thi tank.

/ The supply manifold arrangements include: (1) a largeoxygen cylinder, (2) a small, carefully calibrated "runcylinder" immersed in a water both with thermometer, (3)a large, accurate pressure gauge, and (4) a regulator toreduce pressure to the supply hose.

PROCEDURE

1. Oxygen is supplied from the large cylinder whilethe subject dons the scuba, purges it, and settles down.

2. The large cylinder is shut off and the systemis checked for leaks.

3. When the subject has started swimming, the smallrun cylinder (previously charged from the large cylinder andallowed to equilibrate its temperature is opened. (The

APPENDIX D

subject is watched closely to note any leaks of oxygenfrom the breathing circuit. If any significant leak isnoted, the run is repeated).

4. The gage is read each minute during the run.(Water bath temperature is also recorded periodically).At certain intervals, the subject is instructed to takea full breath. (This brings the system up to a standardvolume, and it is done at such a time that the cylindertemperature and pressure can sterilize before the nextpressure reading).

5. The pressure readings are plotted against time.A "line of best fit" is then drawn on the graph torepresent the mean rate of pressure drop during the"steady state" portion of the run. In drawing the line,most emphasis is placed on the period beyond the first -

5 minutes of the run and on the points which representreadings after the full breaths.

6. The pressure drip over a set interval is measuredfrom the drop-rate line. To obtain the oxygen consumptionvalue in terms of liters of oxygen per minute correctedto standard conditions (STPD), the drop value is multipliedby a single factor which is derived from; (1) the calibrationfactor of the cylinder (see note), (2) the factor forreducing the period of observation to "per minute", (3) anda factor for connecting from ambient (water bath) temperatureto zero degrees centigrade. Separate factors werecalculated for te~iperatures in one degree C. intervals overthe necessary range.

NOTE:

The "cylinder calibration factor" was obtained byapplying the following procedure: (Actually, the factoris for the gage and manifold as well as for the cylinderall high pressure parts involved in the actual runs areincluded in the calibration procedure). The procedureis repeated several times to insure accuracy.

1. Charge cylinder and attach to manifold.2. Allow to cool to room temperature.3. Read pressure accurately.4. Bleed cylinder into large, well-calibrated

spirometer. (Bleed to zero pressure).5. Assure that cylinder and spirometer are at same

temperature, which must be same as that duringinitial pressure reading,.

6. Read volume delivered to spirometer.7. Correct volume to dry gas volume at ambient temperatue

and 760 mm Hg.8. Divide volume by total pressure-drop to determine

volume per p.s.i drop.