MILITARY MEDICINE, 169, 12:994, 2004

Effects of Concurrent Resistance and Aerobic Training on Load-Bearing Performance and the Army Physical Fitness Test

Guarantor; William J. Kraemer. PhDContributors: William J. Kraemer, PhD*: Jason D. Vesco\1, MS*: Jeff S. Volek. PhD RD*: Bradley C. Nindl. PhD+;Robert U. Newton. PhD;̂ : John F. Patton. PhD+; Joseph E. Dziados. MD MPH|: Duncan N. French. PhD*:Keijo Hakkinen. PhD§

The purpose of this research was to determine the effects ofhigh intensity endurance training |ET) and resistance training(RT) alone and in combination on various military tasks. Thir-ty-five male soldiers were randomly assigned to one of fourtraining groups: total body resistance training plus endurancetraining (RT + ET). upper body resistance training plus endur-ance training (UB + ET}. RT only, and ET only. Training wasperformed 4 days per week for 12 weeks. Testing occurredbefore and after the 12-week training regimen. All groups sig-nificantly improved push-up performance, whereas only theRT - ET group did not improve sit-up performance. The groupsthat included ET significantly decreased 2-mile run time, how-ever, only RT - ET and UB t ET showed improved loaded2-mile run time. Leg power increased for groups that includedlower body strengthening exercises (RT and RT + ET). ArmyPhysical Fitness Test performance, loaded running, and legpower responded positively to training, however, it appearsthere is a high degree of specificity when concurrent trainingregimens are implemented.

Introduction

The combination of resistance training (RTl and endurancetraining (ET) is frequently used in athletic, tnilitary, and

civilian populations for performance enhancement. Hickson'originally reported the idea of interference when attempting todevelop strength and cardiovascular endurance concutTenlly.The divergent nature of physiological adaptations for thesemethods has been debated in the literature since then.^^ withsome research showing compromised strength gains, whereasendurance capacity Is unaffected or attenuated with simulta-neous training protocols. '''" '̂ More recently. Hakkinen et al,̂ ' andMcCarthy et al/*^ demonstrated no deleterious effects onstrength developtnent when RT and ET are performed concur-rently. A review by Leveritt et al,̂ outlined acute and chronichypotheses for the possible inhibition during concurrent train-

•Human Performance Laboratory. Department of Kiresiology, University of Con-necticut. Storrs, CT 06269,

'School of Biomedical and Sports Science, Edilh Cowan University, Joondalup,WA, Australia.

iMilitan' Performance Di\1sion, U,S, Army Research Institute of EnvironmentalMedicine, Natick, MA 01760.

§Department of Biolog>' of Physical Activity. P.O, Box 35, 40014, University ofJynaskyla, Jynask\'la. Finland.

The views, opinions, and/or findings contained in this report are those of theauthors and should not be construed as official Department of the Army position,policy, or decision. Human test participants participated in this study after givingtheir free and informed voluntary consent. Investigators adhered to AR 70-25 andUSAMRDC Regulation 70-25 regarding the use of volunteers in research.

This manuscript was received for review in September 2003. The revised manu-script was accepted lor publication in Januarv' 2004,

Reprint & Copyright £ by Association of Military' Surgeons of U.S,, 2004,

ing. which includes factors such as motor recruitment patterns.endocrine responses, and program design.

Optimal readiness for military personnel, however, may notrely heavily on maximal strength (i.e.. lRM) or endurance (i.e.,VOaniaJ- Many tasks require a combination of strength and en-durance (e.g,, loaded carries, repetitive material-handlingtasks). Several investigations provide evidence for improvedmuscular endurance when combining RT and ET or the additionof RT to basic training for military personnel, '""'-'̂ Williams andcolleagues'" have shown heightened performance on maximal(12%) and repetitive (15.5%) box lifting and loaded marching(4,2%) when RT was added to British Army basic training. Mar-cinik et al.''̂ reported significant gains in strength and nochange in aerobic exercise capacity after the addition of circuitweight training to basic training in female Navy recruits.

The RT programs included in concurrent training studieshave been performed in a circuit fashion'''-' or have been ofrelatively short durations (i,e.. 6 weeks).'** It is unclear whetherthe combination of higb-intensity RT and ET performed overlonger periods would elicit similar improvement on standardU,S. military tests as well as a load carry task. Therefore, thepurpose of this investigation was to examine how concurrent RTand ET would impact the Army Physical Fitness Test (APFT), aloaded 2-milc run. and muscular power as measured by maxi-mal vertical jump in male army personnel. It was hypothesizedthat tasks requiring muscular strength and/or endurancewould be improved by impletnenting progressive RT. whereastasks of endurance would benefit from high-intensity aerobictraining.

Methods

Thirty-five active duty men who were soldiers in the U,S, Armywere briefed as to the risks of the investigation and they thenprovided appropriate informed consent by signing a U.S. Armyapproved informed consent document to volunteer to partici-pate in this investigation. Subjects volunteered to go throughthe informed consent process after study briefings on the projectwere conducted at various military bases. All subjects werescreened and had no medical condition that would confound orlimit their ability to fully partake in the study. Subjects wereclassified as physically active soldiers who participated in vari-ous U,S, Army fitness routines to help them with their APFT, butnone were speciftcally trained for or experienced in loaded runson a regular basis. Subject characteristics are presented inTable I. All subjects were boused, fed, trained, and tested onbase at the U.S. Army Natick Research and Engineering Center(Natick, Massachusetts).

Subjects were matched for body size, age, and training status

Medicine, Vol, 169. December 2004 994

Effects of Concurrent Resistance and Aerobic Training 995

TABLE I

SUBJECT CHARACTERISTICS

TABLEm

HYPERTROPHY TRAINING REGIMEN

RT4UBRTET

ETf ET

Height (cm)

174.1 ± 6.4176,7 ±4 ,0175,3 + 6,1177,6 ± 7,8

Weight (kg)

74.2 ± 6.775,6 ± 8.576.6 ± 14.075.3 ± 6.7

Age (years)

23.3 ± 3.622.9 ± 5.024,3 ± 5.121.4 ± 1,4

Values are mean ± SD,

and randomly assigned to one of four training groups. The fourtraining groups were identified as RT + ET; UB + ET: RT only;and ET only. Training was performed for 12 weeks. No exercisewas performed other than the prescribed training for the dura-tion of the experiment, A 2-week familiarization period was usedlo ensure the subjects were accustomed to the experimental andrespective training procedures to minimize improvement fromlearning.

Training Programs

Exercise training was pedbrmed 4 days per week (Monday.Tuesday, Thursday, and Friday) with all sessions individuallysupervised. Endurance workouts started at 8:00 a,m, and re-sistance training workouts started at 1 ;00 p.m, for the ET andRT groups, respectively. The combined training groups (RT -̂ ETand UB + ET) waited 5 to 6 hours after their endurance workout(0 perform RT, All subjects completed 100% of the trainingsessions. As subjects improved in strength and/or endurance(i.e,, weightlifting repetitions performed, post-run heart rate,treadmill testing, or rim times) workout intensities were pro-gressively increased within the constraints of each exercise pro-gram (load increased for the strength programs whereas exer-cise/rest ratios were decreased and run speeds increased forendurance training). For those subjects performing combinedtraining (RT ^ ET and UB + ET), RT sessions were split duringthe week and paired with am workouts so that on each trainingday only one of the exercise protocols (i,e.. hypertrophy or sprintinterval) produced high levels of blood lactate (>10 mmol • L ').

The RT program consisted of varied workouts within eachweek (i.e.. nonlinear periodization) designed to enhance musclehypertrophy and strength.'' Tables 11 and III detail each proto-

TABLE II

STRENGTH TRAINING REGIMEN

Body Area

Upper body exercisesBench pressShoulder pressBleep curlsLat pulldown

Lower body exercisesDead lift1-eg pressLeg extensionCalf raises

Trunk exercisesObliquesSit-ups

Sets

5555

4553

55

RepetitionMaximum

5555

655

10

1010

Rest (minutes)

2-32-32-32-3

2-32-32-32-3

Body Area

Upper body supersets"Bench press + (best flysShoulder press + uprif^hl rowLat pulldown + seated rowBicep curls

Lower body supersetsSingle leg extension + leg curlSplit squatsCall' raises

Trunk exercisesSit-ups

Sets

3233

333

2

RepetitionMaximum

10101010

101015

25

Rest(minutes)

1111

111

1

" Supersets, a pair of exercises performed in succession without rest.

co!. Hypertrophy protocols were performed on Mondays andThursdays and strength protocols were performed on Tuesdaysand Fridays,

The ET program consisted of long distance and sprint inter\'altraining to provide variation. L/ing distance runs were per-formed on Mondays and Thursdays and sprint intervals werecompleted on Tuesdays and Fridays. Exercise prescriptionswere based upon measures of heart rate acquired during tread-mil! testing,''' The long distance training was performed on a1 -mile course of varying terrain with each subject running as faras they could in 40 minutes. Every 4 weeks, heart rate wasmonitored after every mile to maintain running intensity be-tween 70 and 80% VO;̂ ,,,.,,. As the study progressed over the12-week training protocol, the distance covered during eachsession increased. Approximately 80% of total running volumeconsisted of long distance training. All sprint interval sessions100 to 400 meters were performed on a 400-meter track. Thedistance of sprint intervals ranged from 400 to 800 meters, andexercise-to-rest ratios progressed from 1:4 to 1:0.5 over the] 2-week study period. Intensity was maintained between 90and 100% V02,,,,ix based on heart rate after each interval. No loadcarriage practice was undertaken during the course of the studyto determine how well the conditioning programs alone wouldtranslate to the military task and therefore limit injury exposureof ruck sack training,

TABLE IV

CHANGES IN APFT PERFORMANCE

RT + ETPrePost

UB + ETPrePost

RTPrePost

ETPrePost

Push-Ups

62.8 + 13.687.2 ± 11.2"

50.6 - 13,068.3 = 17.9"

51.2 - 9.873.4 ± 11.7"

44.5 ± 10.252.4 ± 9 . 1 "

Sit Ups

68.9 ±11.784,7 ± 7.8

58,4 ± 12,672,8 ± 17,2"

52.9 ± 7.872.8 ± 4.2"

47,6 ± 7,055.0 ± 8.5"

2-Mile Run (s)

804 ± 96732 ± 66"

906 ± 42798 ± 60"

888 ± 78888 ± 84

924 ± 168804 ± 114"

Values are mean ± SD." Significant difference pre- and post performance (p < 0,05).

^ Medicine. Vo), 169, December 2004

996 Effects of Concurrent Resistance and Aerobic Training

Testing

The APFT was performed according to FM 21-20. Subjectscompleted all three tests within 2 hours. All subjects had pre-vious experience and were familiar with testing protocols. First,push-ups (maximum in 2 minutes) were performed in a stan-dard push-up position ulth the body in a straight line the sub-ject descends until the upper arms are parallel with the groundand then raising the body until the arms are fully extended.Next, sit-ups (maximum in 2 minutes) were performed. Subjectslaid flat on the ground with knees bent at 90 degrees and fingersinterlocked behind the head uith another subject holding thefeet with only their hands. A repetition was counted when thebody is brought up to the vertical position and returned until theshoulder blades touch the ground. Finally, a 400-meter trackwas used to for the 2-mile run (unloaded). Subjects were in-stmcted to complete the course in the shortest time possible. Aminimum of 10 minutes and maximum of 20 minutes rest wasallowed between tests.

A maximal effort 2-mile loaded run was performed on thesame 400-meter track described while carrying 44.7 kg (Alicepack. Battle Dress Uniforms, boots, and pack load]. Again, sub-jects were instructed to complete the course in the shortest timepossible. Immediately after completion of the run. heart rate andrating of perceived exertion"' were recorded.

Maximal effort countermovement jump height was used toassess leg power using a pre\1ously described protocol.'' Eachsubject performed three jumps without an approach step andthe best score was recorded. Ample rest (--2 minutes) was pro-vided between attempts.

Body composition analysis was accomplished with hydro-static weighing technology previously described in detail.'^ Thepercentage body fat was estimated using the Siri equation."*

Statistical Analysis

All data are presented as mean t SD, Data were analyzedusing (group "̂ time) repeated measures analysis of variance.When significant main effects and/or interactions were ob-served, a Fisher least-significant difference or Tukey post hoctest was used where appropriate to determine pairwise differ-ences. Test-retest reliability intraclass Rs for the dependent

variables was R > 0.92. Statistical power calculations for thisstudy ranged from 0.84 to 0.95. The level of significance set forthe investigation was p < 0.05.

Results

No injuries were obser\̂ ed as a result of participating in thisinvestigation: however, one subject in tbe ET group dropped outbecause of an acute hernia in the first week of training.

APFT performance responded positively to training (Table W]. Allgroups significantly improved push-up performance [p < 0.05):however, groups involved with RT tended to show larger gains(35-43%) than ET only (18%). Although all groups increased thenumber of sit-ups performed in 2 minutes, the RT ^ ET group didnot reach statistical significance. All groups performing ET showedsignificant (p < 0.05) decreases in the unloaded 2-mile run time.

No changes were observed for heart rate or ratings of per-ceived exertion immediately after the 2-mile loaded run. Onlythe groups performing concurrent training showed significantimprovements in time to completion (Table V and Fig. 2).

Figure 1 illustrates the changes in leg power as measured bycountermovement jump performance. Only the two groups per-forming RT. which involved multijoint exercises for the legs,showed significant increases in jump height (p < 0.05).

Table VI shows the changes in body composition. All groupsperforming ET decreased their percentage body fat (p < 0.01),whereas all groups performing RT increased fat-free mass (FFM)

Discussion

The data from this investigation indicate the APFT respondspositively to both methods of training regardless of performingthem independently or concurrently (Table IV). However, theredoes appear to be some degree of specificity. Although perform-ing RT was not necessary for improvements, as evidence by ETsignificantly improving on all three tests, the gains observedwhen RT was included were greater for push-ups (38-41 vs.18%) and sit-ups (23-38 vs. 17%). On the other hand, changesin 2-mile run performance were mixed. The greatest decrease in

TABLE V

RESPONSES AND CHANGES TO 2-MILE LOAD-BEARING TASK

RT + ETPrePost

UB ^ ETPrePost

RT

PrePost

ETPrePost

Pre-Run

72.2 ± 9.882.8 ± 10.7

78.0 ± 20.879.5 ± 7.5

80.2 ±11.185.1 ± 8.1

86.4 ±15.191.5 ± 19.2

Heart Rate

Immediately Post-Run

205.2 ± 6.6199.2 ± 8.8

201.0 ± 14.3196.1 ± 12.9

186.0 ± i7.9178.0 ± 15.3

192.0 ±11.2183.6 ± 10.3

Ratings of Perceived Exertion

18.0 ± 1.419.0 ± 0.7

18.0 ± 1.9t7.5 ± 1.9

16.5 ± 2.517.9 ± 1.8

16.6 ± 1.617.4 ± 1.7

Time (s)

1518 ± 2531305 ± 164"

1717 ± 1711532 ± 186°

1767 ± 2021692 ± 215

1832 ± 3191831 ± 383

Values are mean ± SD." Significant difference pre- and postperformanre (p < 0.05).

Military Medicine, Vol. 169. December 2004

Effects of Concurrent Resistance and Aerobic- Traininji 997

RT+ET UB+ET

Fig. 1. Changes in vertical jump height after training. *, Significantly greater compared with pretest.

time occurred as a result of ET, whereas RT showed no change.Interestingly, the coneurretit ffroups showed a large disparitywith RT - ET itnproving 4% compared with UB + ET improving12%. These results are sitnilar to others iti the literature'^''''^and seem to support an acute hypothesis'' that suggests thatresidual fatigue from ET inhibits the ability to generate forceduring subsequent RT. Although a significant amount of timewas allowed between sessions during coneurrent training in thepresent study. Sale et a\:^ reported greater strength gains whenconcurrent training was performed on separate days comparedwith the same day. It eould be argued thai aerobic endurancewas affected in a similar fashion hy performing lower body RT onthe same day. whereas UB + RT did not include any lower bodyRT and therefore encountered no interference on aerobic perfor-mance.

Loaded nmning/marching is a typical military task." '̂̂ ° Ourresults suggest eoncurrent training is important and possiblynecessary to achieve improvement for this type of task (Table V].Only the groups perfomiing eoneurrent training significantlydecreased time to completion, whereas RT and ET alone showedno change in performance. Previously, Kraemer et al,̂ *' showedsimilar improvements for military women performing concur-rent and aerohic only training, Williams et al."^ also reportedimprovements in loaded marching when heavy RT was ineludedwith basic training; however, these differences were not signifi-eantly different from normal basic training. An apparent eon-founding faetor was that basic training included loaded march-ing, therefore, their results must be interpreted with eaution.

Although it appears RT is beneficial to load-bearing tasks, the

contribution of the upper versus lower body musculature re-mains less elear. An interesting finding from our data showsthat UB -t- CT significantly improved time to completion similarto RT + ET (- 188 vs. -213 s. respectively). A direet mechanismby which upper body strength and/or stability contributes toload carrying ability cannot be determined from our data, butmaintenance of proper posture and subsequent reduction ofenergy expenditure is one possible explanation. Figure 2 showsthe high degree of speeifleity in loaded and unloaded 2-mileruns; however, more research is neeessary to decipher the in-teraetion of resistance (upper and lower body) and aerobic train-ing on repetitive loaded tasks.

Changes in body composition are typically observed afterehronic resistanee and/or aerohic training favoring an increasein FFM and a deerease in the percentage of body fat.*̂ "*'̂ -̂ ""̂ ^Recently, Sharp and colleagues^' provided a eross-seetional re-port on changes in body composition for U.S. Army recruitsbetween 1978 and 1998. They indicated that the percentage offat had increased from 16.2 to 18.7% for men. Our results fallwithin this range, and posttests are closer to the lower end range(Table VI). The percentage of body fat decreased in only thosegroups perlbrming ET. whereas FFM only increased in groupsperforming RT regardless of ET inclusion. This would suggestthat hypertrophy was not inhibited by concurrent training yetdifferences among groups oeeur.'-'' Overall, it appears concur-rent training provides a beneficial stimulus for altering bodycomposition in military personnel.

Vertical jump was used to assess lower body power. Only the

MiUtar>' Medicine. Vol. 169. December 2004

998 Effects of Concurrent Resistance and Aerobic Training

RT+ET UB+ET

Fig. 2. Comparison of percentage of improvement between loaded and unloaded 2-mile runs,between loaded and unloaded runs,

K Significantly greater compared with pretest. +, Significant difference

TABLE Vi

CHANGES IN BODY COMPOSITION

Pre

PosfUB + ET

Pre

Post

RT

Pre

Post

ET

Pre

Post

Body Mass (kg)

74.2 ± 6.7

73.7 ± 6.5

75.6 ± 8.576.4 + 8.4

76.6 ± t4.0

79.0 ± t6.1"

75.3 ± 6.774.4 ± 4.6

FFM (kg)

63.6 ± 5.9

65.9 ± 5.3"

62.0 ± 1.1

64.8 ± 6.4"

61.8 ± 7.t

64.1 ± 7.9"

61.1 r 3.6

62.1 ±3 .6

% Body Fat

13.t ±6.1

9.8 ± 5,1"

17.4 r 2.9

14.6 r 3.5"

18.3 ± 1.1

16.9 ± 8.0

18.5^7.1

16.2 ± 2.6°

Values are mean ± SD.

" Significant diffcrenee pre- and post performance (p < 0.01|.

groups performing RT. which included multiple joint leg exer-cises and improved jump height (Fig. I|. Interestingly. RT + ETand RT improved 8.7%. which would indicate a lack of interfer-ence with concurrent training. These results do not agree withrecent findings from Hakkinen ct al..'' who found similarstrength, and activation improvements, but dampened rate offorce development when comparing strength and ET combinedagainst strength training alone. Ditterences in testing modalitiesmay play a role in the discrepancy.

The APFT was selectively responsive to resistance and endur-ance training performed alone or concurrently. An intriguingfinding was that upper body strength played a significant role inenhancing a 2-mile loaded run performance. Favorable changeswere observed for body composition as well as lower body powerwhen resistance exercise was included in the training regimen.Based on these results, performance enhancement militarytasks respond positively to various aspects of both types oftraining, however, the appropriate timing, volume, and type ofexercise are essential elements to acquiring a targeted outcome.

Acknowledgments

We thank our colleagues and university iaboratory staffs and the U.S.

Army Research Institute of Environmental Medicine, Natiek. Massachu-

setts, for iheir scientific and technical contributions, and for a dedicated

group of participants who made this research possible.

References

1. Hickson RC: interference of strength dcvt'lopnien! by simultaneously training forstrength and endurance. Eur J Appl Phvsiol Otcup Physidl 1980; 45: 255-69.

2. Dudley GA. Djaniil R: Incompatibility of endurance- and slrengtlvtralninji modesof"exercise. J Appl Physiol 1985; 59: 1446-51,

3. Sale DG. Jacobs I. MacDougall JD. Gamer S: Comparison oi two regtmens ofconcurrent slrength and endurance training. Med Sci Sports Exeru 1990; 22;348-56.

4. Bell GJ. Syrotuik D, Martin TP. Bumham R. Quinney HA; Effect of concurrentstrengtfi and (.'nciuranLe training on skeletal muscle properties and bominiie

Militar\' Medicine. Vol. 169. December 2004

Effects of Concurrent Resistance and Aerobic Training 999

concentrations in humans. Eur J Appl Physiol 2000; 81: 418-27.5, Hennessey LC, WatsonAWS:Theinierferen(eefl'ectsol training for strength and

endurance siniullaneously. J Strength Cond Res 1994: 8: 12-9.

6, Hakkinen K, Alen M, Kraemer WJ, el al; Neuromuseiilar adaptations duringconcurrent strength and endurance I rain ing versus strength Iraining, Eur J ApplPhysiol 2003: 89: 42-52.

7, McCarthyJP.AgreJC, Graf UK, Fozniak MA, Vailas AC: Compalibilityol adaptiveresponses with combining strength and endurance training, Med Sci SportsExerc 1995:27:429-36.

8, McCarthy JP, Pozniak MA, Agrc JC: Neuromuseiilar adaptations to concurrentstrenfilh and endurance training, Med Sci SpoHs Exerc 2002: 34: 511-9,

9, Leveritt M, Abemethy PJ, Barry BK, Logan PA: Concurrent strength and endur-ance training: a review. Sports Med 1999: 28: 413-27.

10, Williams AG, Rayson MP, Jones DA: Resistance training and the enhancement ofthe gains in maledal-handling ability and physical Illness of British Amiy re-cruits during basic training. Ergonomics 2002: 45: 267-79.

1 i. Williams AG, Rayson MI', Janes DA: Effects of basic training on material handlingability and physical fitness oli3dtish Army recruits. Ergonomics 1999:42:1114-24,

12, Knapik JJ: The inlluenrc of physical filness training on the manual materialhandling capability of women. Appl Ergon 1997: 28: 339-45,

13, Marcinik E-}. Hodgdon JA. O'Brien JJ, Mitileiiian K: Fitness changes of Navalwomen follouing aerobic based programs fraiuring calisthenic or circuit weighttraining exercises. Eur J Appl Physiol Occup Physiol 1985: 54: 244-9,

14, Fleck SJ, Kraemer WJ: Designing Resistance Training Programs, Champaign, IL,Human Kinetics, 1997.

15, Kraemer WJ, Patton J. Gordon SE, et al: Compatibility of high intensity' strengthand endurance Irainlng on hormonal and skeletal muscle adaptations, J ApplPhysiol 1995: 78: 976-89,

16, Borg GAV: Perceived exertion as an iiidicalor of somatic stress, Srand J RehabMed 1970:2:92-8,

17, Fox EL, Malhews DK: The Physiological Basis ofPhysicai Educalion and Athlet-ics, Ed 3, Philadelphia, PA, Saunders, 1981,

18, Nindl EiC, Kraemer WJ, Eminert WH, el al: Comparison of body lompositionassessment among lean black and white male collegiate athletes, Med Sci SportsExerc 1998:30:769-76,

19, Siri WE: Body composition from lluid spaces and density: analysis of methods. In:Techniques for Measuring Body Composition, pp 223-244, Edited by Broicek J,Hanschel A, Washiuglon, DC, National Academy of Sciences, 1961,

20, Kraemer WJ, Mazzetti SA, Nindl BC, et al: Effecl of resistance training on wom-eii's strength/power and occupalional performances, Med Sci Sports Exer 2001:33: 1011-25,

21, Sharp MA, Patton JF, KnapikJJ, eta!: Contparison of the physical fitness of menand women entering the U,S, Army: 1978-1998. Med Sci Sports Exerc 2002: 34:356-63,

22, Uolezal BA. Potteiger JA: Concurrent resistance and endurance training influ-ence basal metabolic rate in nondieting individuals. J Appl Physiol 1998; 85:695-700,

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Military Medicine, Vo!, 169, December 2004