MILITARY MEDICINE, 169, 12:994, 2004 Effects of Concurrent Resistnce nd Aerobic Trining on Lod- Bering Performnce nd the Army Physicl Fitness Test Gurntor: Willim J. Kremer, PhD Contributors: Willim J. Kremer, PhD*; Json D. Vescovi, MS*; Jeff S. Volek, PhD RD*; Brdley C. Nindl, PhD ; Robert U. Newton, PhD ; John F. Ptton, PhD ; Joseph E. Dzidos, MD MPH ; Duncn N. French, PhD*; Keijo Häkkinen, PhD The purpose of this reserch ws to determine the effects of high intensity endurnce trining (ET) nd resistnce trining (RT) lone nd in combintion on vrious militry tsks. Thirty-five mle soldiers were rndomly ssigned to one of four trining groups: totl body resistnce trining plus endurnce trining (RT ET), upper body resistnce trining plus endurnce trining (UB ET), RT only, nd ET only. Trining ws performed 4 dys per week for 12 weeks. Testing occurred before nd fter the 12-week trining regimen. All groups significntly improved push-up performnce, wheres only the RT ET group did not improve sit-up performnce. The groups tht included ET significntly decresed 2-mile run time, however, only RT ET nd UB ET showed improved loded 2-mile run time. Leg power incresed for groups tht included lower body strengthening exercises (RT nd RT ET). Army Physicl Fitness Test performnce, loded running, nd leg power responded positively to trining, however, it ppers there is high degree of specificity when concurrent trining regimens re implemented. Introduction he combintion of resistnce trining (RT) nd endurnce T trining (ET) is frequently used in thletic, militry, nd civilin popultions for performnce enhncement. Hickson 1 originlly reported the ide of interference when ttempting to develop strength nd crdiovsculr endurnce concurrently. The divergent nture of physiologicl dpttions for these methods hs been debted in the literture since then, 2,3 with some reserch showing compromised strength gins, wheres endurnce cpcity is unffected or ttenuted with simultneous trining protocols. 1,3 5 More recently, Häkkinen et l. 6 nd McCrthy et l. 7,8 demonstrted no deleterious effects on strength development when RT nd ET re performed concurrently. A review by Leveritt et l. 9 outlined cute nd chronic hypotheses for the possible inhibition during concurrent trin- *Humn Performnce Lbortory, Deprtment of Kinesiology, University of Connecticut, Storrs, CT 06269. School of Biomedicl nd Sports Science, Edith Cown University, Joondlup, WA, Austrli. Militry Performnce Division, U.S. Army Reserch Institute of Environmentl Medicine, Ntick, MA 01760. Deprtment of Biology of Physicl Activity, P.O. Box 35, 40014, University of Jynäskylä, Jynäskylä, Finlnd. The views, opinions, nd/or findings contined in this report re those of the uthors nd should not be construed s officil Deprtment of the Army position, policy, or decision. Humn test prticipnts prticipted in this study fter giving their free nd informed voluntry consent. Investigtors dhered to AR 70-25 nd USAMRDC Regultion 70-25 regrding the use of volunteers in reserch. This mnuscript ws received for review in September 2003. The revised mnuscript ws ccepted for publiction in Jnury 2004. Reprint & Copyright by Assocition of Militry Surgeons of U.S., 2004. ing, which includes fctors such s motor recruitment ptterns, endocrine responses, nd progrm design. Optiml rediness for militry personnel, however, my not rely hevily on mximl strength (i.e., 1RM) or endurnce (i.e., VO 2mx ). Mny tsks require combintion of strength nd endurnce (e.g., loded crries, repetitive mteril-hndling tsks). Severl investigtions provide evidence for improved musculr endurnce when combining RT nd ET or the ddition of RT to bsic trining for militry personnel. 10 13 Willims nd collegues 10 hve shown heightened performnce on mximl (12%) nd repetitive (15.5%) box lifting nd loded mrching (4.2%) when RT ws dded to British Army bsic trining. Mrcinik et l. 13 reported significnt gins in strength nd no chnge in erobic exercise cpcity fter the ddition of circuit weight trining to bsic trining in femle Nvy recruits. The RT progrms included in concurrent trining studies hve been performed in circuit fshion 11,13 or hve been of reltively short durtions (i.e., 6 weeks). 10 It is uncler whether the combintion of high-intensity RT nd ET performed over longer periods would elicit similr improvement on stndrd U.S. militry tests s well s lod crry tsk. Therefore, the purpose of this investigtion ws to exmine how concurrent RT nd ET would impct the Army Physicl Fitness Test (APFT), loded 2-mile run, nd musculr power s mesured by mximl verticl jump in mle rmy personnel. It ws hypothesized tht tsks requiring musculr strength nd/or endurnce would be improved by implementing progressive RT, wheres tsks of endurnce would benefit from high-intensity erobic trining. Methods Thirty-five ctive duty men who were soldiers in the U.S. Army were briefed s to the risks of the investigtion nd they then provided pproprite informed consent by signing U.S. Army pproved informed consent document to volunteer to prticipte in this investigtion. Subjects volunteered to go through the informed consent process fter study briefings on the project were conducted t vrious militry bses. All subjects were screened nd hd no medicl condition tht would confound or limit their bility to fully prtke in the study. Subjects were clssified s physiclly ctive soldiers who prticipted in vrious U.S. Army fitness routines to help them with their APFT, but none were specificlly trined for or experienced in loded runs on regulr bsis. Subject chrcteristics re presented in Tble I. All subjects were housed, fed, trined, nd tested on bse t the U.S. Army Ntick Reserch nd Engineering Center (Ntick, Msschusetts). Subjects were mtched for body size, ge, nd trining sttus 994
Effects of Concurrent Resistnce nd Aerobic Trining 995 TABLE I SUBJECT CHARACTERISTICS Height (cm) Weight (kg) Age (yers) RT ET 174.1 6.4 74.2 6.7 23.3 3.6 UB ET 176.7 4.0 75.6 8.5 22.9 5.0 RT 175.3 6.1 76.6 14.0 24.3 5.1 ET 177.6 7.8 75.3 6.7 21.4 1.4 nd rndomly ssigned to one of four trining groups. The four trining groups were identified s RT ET; UB ET; RT only; nd ET only. Trining ws performed for 12 weeks. No exercise ws performed other thn the prescribed trining for the durtion of the experiment. A 2-week fmiliriztion period ws used to ensure the subjects were ccustomed to the experimentl nd respective trining procedures to minimize improvement from lerning. TABLE II STRENGTH TRAINING REGIMEN Body Are Sets Repetition Mximum Rest (minutes) Upper body exercises Bench press 5 5 2 3 Shoulder press 5 5 2 3 Bicep curls 5 5 2 3 Lt pulldown 5 5 2 3 Lower body exercises Ded lift 4 6 2 3 Leg press 5 5 2 3 Leg extension 5 5 2 3 Clf rises 3 10 2 3 Trunk exercises Obliques 5 10 Sit-ups 5 10 TABLE III HYPERTROPHY TRAINING REGIMEN Body Are Sets Repetition Mximum Trining Progrms Exercise trining ws performed 4 dys per week (Mondy, Tuesdy, Thursdy, nd Fridy) with ll sessions individully supervised. Endurnce workouts strted t 8:00.m. nd resistnce trining workouts strted t 1:00 p.m. for the ET nd RT groups, respectively. The combined trining groups (RT ET nd UB ET) wited 5 to 6 hours fter their endurnce workout to perform RT. All subjects completed 100% of the trining sessions. As subjects improved in strength nd/or endurnce (i.e., weightlifting repetitions performed, post-run hert rte, tredmill testing, or run times) workout intensities were progressively incresed within the constrints of ech exercise progrm (lod incresed for the strength progrms wheres exercise/rest rtios were decresed nd run speeds incresed for endurnce trining). For those subjects performing combined trining (RT ET nd UB ET), RT sessions were split during the week nd pired with run workouts so tht on ech trining dy only one of the exercise protocols (i.e., hypertrophy or sprint intervl) produced high levels of blood lctte ( 10 mmol L 1 ). The RT progrm consisted of vried workouts within ech week (i.e., nonliner periodiztion) designed to enhnce muscle hypertrophy nd strength. 14 Tbles II nd III detil ech protocol. Hypertrophy protocols were performed on Mondys nd Thursdys nd strength protocols were performed on Tuesdys nd Fridys. The ET progrm consisted of long distnce nd sprint intervl trining to provide vrition. Long distnce runs were performed on Mondys nd Thursdys nd sprint intervls were completed on Tuesdys nd Fridys. Exercise prescriptions were bsed upon mesures of hert rte cquired during tredmill testing. 15 The long distnce trining ws performed on 1-mile course of vrying terrin with ech subject running s fr s they could in 40 minutes. Every 4 weeks, hert rte ws monitored fter every mile to mintin running intensity between 70 nd 80% VO 2mx. As the study progressed over the 12-week trining protocol, the distnce covered during ech session incresed. Approximtely 80% of totl running volume consisted of long distnce trining. All sprint intervl sessions 100 to 400 meters were performed on 400-meter trck. The distnce of sprint intervls rnged from 400 to 800 meters, nd exercise-to-rest rtios progressed from 1:4 to 1:0.5 over the 12-week study period. Intensity ws mintined between 90 nd 100% VO 2mx bsed on hert rte fter ech intervl. No lod crrige prctice ws undertken during the course of the study to determine how well the conditioning progrms lone would trnslte to the militry tsk nd therefore limit injury exposure of ruck sck trining. TABLE IV CHANGES IN APFT PERFORMANCE Push-Ups Sit-Ups 2-Mile Run (s) RT ET Pre 62.8 13.6 68.9 11.7 804 96 Post 87.2 11.2 84.7 7.8 732 66 UB ET Pre 50.6 13.0 58.4 12.6 906 42 Post 68.3 17.9 72.8 17.2 798 60 RT Pre 51.2 9.8 52.9 7.8 888 78 Post 73.4 11.7 72.8 4.2 888 84 ET Pre 44.5 10.2 47.6 7.0 924 168 Post 52.4 9.1 55.0 8.5 804 114 Significnt difference pre- nd postperformnce (p 0.05). Rest (minutes) Upper body supersets Bench press chest flys 3 10 1 Shoulder press upright row 2 10 1 Lt pulldown seted row 3 10 1 Bicep curls 3 10 1 Lower body supersets Single leg extension leg curl 3 10 1 Split squts 3 10 1 Clf rises 3 15 1 Trunk exercises Sit-ups 2 25 1 Supersets, pir of exercises performed in succession without rest.
996 Effects of Concurrent Resistnce nd Aerobic Trining Testing The APFT ws performed ccording to FM 21-20. Subjects completed ll three tests within 2 hours. All subjects hd previous experience nd were fmilir with testing protocols. First, push-ups (mximum in 2 minutes) were performed in stndrd push-up position with the body in stright line the subject descends until the upper rms re prllel with the ground nd then rising the body until the rms re fully extended. Next, sit-ups (mximum in 2 minutes) were performed. Subjects lid flt on the ground with knees bent t 90 degrees nd fingers interlocked behind the hed with nother subject holding the feet with only their hnds. A repetition ws counted when the body is brought up to the verticl position nd returned until the shoulder bldes touch the ground. Finlly, 400-meter trck ws used to for the 2-mile run (unloded). Subjects were instructed to complete the course in the shortest time possible. A minimum of 10 minutes nd mximum of 20 minutes rest ws llowed between tests. A mximl effort 2-mile loded run ws performed on the sme 400-meter trck described while crrying 44.7 kg (Alice pck, Bttle Dress Uniforms, boots, nd pck lod). Agin, subjects were instructed to complete the course in the shortest time possible. Immeditely fter completion of the run, hert rte nd rting of perceived exertion 16 were recorded. Mximl effort countermovement jump height ws used to ssess leg power using previously described protocol. 17 Ech subject performed three jumps without n pproch step nd the best score ws recorded. Ample rest ( 2 minutes) ws provided between ttempts. Body composition nlysis ws ccomplished with hydrosttic weighing technology previously described in detil. 18 The percentge body ft ws estimted using the Siri eqution. 19 Sttisticl Anlysis All dt re presented s men SD. Dt were nlyzed using (group time) repeted mesures nlysis of vrince. When significnt min effects nd/or interctions were observed, Fisher lest-significnt difference or Tukey post hoc test ws used where pproprite to determine pirwise differences. Test-retest relibility intrclss Rs for the dependent vribles ws R 0.92. Sttisticl power clcultions for this study rnged from 0.84 to 0.95. The level of significnce set for the investigtion ws p 0.05. Results No injuries were observed s result of prticipting in this investigtion; however, one subject in the ET group dropped out becuse of n cute herni in the first week of trining. APFT performnce responded positively to trining (Tble IV). All groups significntly improved push-up performnce (p 0.05); however, groups involved with RT tended to show lrger gins (35 43%) thn ET only (18%). Although ll groups incresed the number of sit-ups performed in 2 minutes, the RT ET group did not rech sttisticl significnce. All groups performing ET showed significnt (p 0.05) decreses in the unloded 2-mile run time. No chnges were observed for hert rte or rtings of perceived exertion immeditely fter the 2-mile loded run. Only the groups performing concurrent trining showed significnt improvements in time to completion (Tble V nd Fig. 2). Figure 1 illustrtes the chnges in leg power s mesured by countermovement jump performnce. Only the two groups performing RT, which involved multijoint exercises for the legs, showed significnt increses in jump height (p 0.05). Tble VI shows the chnges in body composition. All groups performing ET decresed their percentge body ft (p 0.01), wheres ll groups performing RT incresed ft-free mss (FFM) (p 0.01). Discussion The dt from this investigtion indicte the APFT responds positively to both methods of trining regrdless of performing them independently or concurrently (Tble IV). However, there does pper to be some degree of specificity. Although performing RT ws not necessry for improvements, s evidence by ET significntly improving on ll three tests, the gins observed when RT ws included were greter for push-ups (38 41 vs. 18%) nd sit-ups (23 38 vs. 17%). On the other hnd, chnges in 2-mile run performnce were mixed. The gretest decrese in TABLE V RESPONSES AND CHANGES TO 2-MILE LOAD-BEARING TASK Hert Rte Pre-Run Immeditely Post-Run Rtings of Perceived Exertion Time (s) RT ET Pre 72.2 9.8 205.2 6.6 18.0 1.4 1518 253 Post 82.8 10.7 199.2 8.8 19.0 0.7 1305 164 UB ET Pre 78.0 20.8 201.0 14.3 18.0 1.9 1717 171 Post 79.5 7.5 196.1 12.9 17.5 1.9 1532 186 RT Pre 80.2 11.1 186.0 17.9 16.5 2.5 1767 202 Post 85.1 8.1 178.0 15.3 17.9 1.8 1692 215 ET Pre 86.4 15.1 192.0 11.2 16.6 1.6 1832 319 Post 91.5 19.2 183.6 10.3 17.4 1.7 1831 383 Significnt difference pre- nd postperformnce (p 0.05).
Effects of Concurrent Resistnce nd Aerobic Trining 997 Fig. 1. Chnges in verticl jump height fter trining., Significntly greter compred with pretest. time occurred s result of ET, wheres RT showed no chnge. Interestingly, the concurrent groups showed lrge disprity with RT ET improving 4% compred with UB ET improving 12%. These results re similr to others in the literture 4,6,21 nd seem to support n cute hypothesis 9 tht suggests tht residul ftigue from ET inhibits the bility to generte force during subsequent RT. Although significnt mount of time ws llowed between sessions during concurrent trining in the present study, Sle et l. 3 reported greter strength gins when concurrent trining ws performed on seprte dys compred with the sme dy. It could be rgued tht erobic endurnce ws ffected in similr fshion by performing lower body RT on the sme dy, wheres UB RT did not include ny lower body RT nd therefore encountered no interference on erobic performnce. Loded running/mrching is typicl militry tsk. 10,20 Our results suggest concurrent trining is importnt nd possibly necessry to chieve improvement for this type of tsk (Tble V). Only the groups performing concurrent trining significntly decresed time to completion, wheres RT nd ET lone showed no chnge in performnce. Previously, Kremer et l. 20 showed similr improvements for militry women performing concurrent nd erobic only trining. Willims et l. 10 lso reported improvements in loded mrching when hevy RT ws included with bsic trining; however, these differences were not significntly different from norml bsic trining. An pprent confounding fctor ws tht bsic trining included loded mrching, therefore, their results must be interpreted with cution. Although it ppers RT is beneficil to lod-bering tsks, the contribution of the upper versus lower body musculture remins less cler. An interesting finding from our dt shows tht UB ET significntly improved time to completion similr to RT ET ( 188 vs. 213 s, respectively). A direct mechnism by which upper body strength nd/or stbility contributes to lod crrying bility cnnot be determined from our dt, but mintennce of proper posture nd subsequent reduction of energy expenditure is one possible explntion. Figure 2 shows the high degree of specificity in loded nd unloded 2-mile runs; however, more reserch is necessry to decipher the interction of resistnce (upper nd lower body) nd erobic trining on repetitive loded tsks. Chnges in body composition re typiclly observed fter chronic resistnce nd/or erobic trining fvoring n increse in FFM nd decrese in the percentge of body ft. 6,10,12,20 22 Recently, Shrp nd collegues 21 provided cross-sectionl report on chnges in body composition for U.S. Army recruits between 1978 nd 1998. They indicted tht the percentge of ft hd incresed from 16.2 to 18.7% for men. Our results fll within this rnge, nd posttests re closer to the lower end rnge (Tble VI). The percentge of body ft decresed in only those groups performing ET, wheres FFM only incresed in groups performing RT regrdless of ET inclusion. This would suggest tht hypertrophy ws not inhibited by concurrent trining yet differences mong groups occur. 15 Overll, it ppers concurrent trining provides beneficil stimulus for ltering body composition in militry personnel. Verticl jump ws used to ssess lower body power. Only the
998 Effects of Concurrent Resistnce nd Aerobic Trining Fig. 2. Comprison of percentge of improvement between loded nd unloded 2-mile runs., Significntly greter compred with pretest., Significnt difference between loded nd unloded runs. TABLE VI CHANGES IN BODY COMPOSITION Body Mss (kg) FFM (kg) % Body Ft RT ET Pre 74.2 6.7 63.6 5.9 13.1 6.1 Post 73.7 6.5 65.9 5.3 9.8 5.1 UB ET Pre 75.6 8.5 62.0 7.7 17.4 2.9 Post 76.4 8.4 64.8 6.4 14.6 3.5 RT Pre 76.6 14.0 61.8 7.1 18.3 7.7 Post 79.0 16.1 64.1 7.9 16.9 8.0 ET Pre 75.3 6.7 61.1 3.6 18.5 7.1 Post 74.4 4.6 62.1 3.6 16.2 2.6 Significnt difference pre- nd postperformnce (p 0.01). groups performing RT, which included multiple joint leg exercises nd improved jump height (Fig. 1). Interestingly, RT ET nd RT improved 8.7%, which would indicte lck of interference with concurrent trining. These results do not gree with recent findings from Häkkinen et l., 6 who found similr strength, nd ctivtion improvements, but dmpened rte of force development when compring strength nd ET combined ginst strength trining lone. Differences in testing modlities my ply role in the discrepncy. The APFT ws selectively responsive to resistnce nd endurnce trining performed lone or concurrently. An intriguing finding ws tht upper body strength plyed significnt role in enhncing 2-mile loded run performnce. Fvorble chnges were observed for body composition s well s lower body power when resistnce exercise ws included in the trining regimen. Bsed on these results, performnce enhncement militry tsks respond positively to vrious spects of both types of trining, however, the pproprite timing, volume, nd type of exercise re essentil elements to cquiring trgeted outcome. Acknowledgments We thnk our collegues nd university lbortory stffs nd the U.S. Army Reserch Institute of Environmentl Medicine, Ntick, Msschusetts, for their scientific nd technicl contributions, nd for dedicted group of prticipnts who mde this reserch possible. References 1. Hickson RC: Interference of strength development by simultneously trining for strength nd endurnce. Eur J Appl Physiol Occup Physiol 1980; 45: 255 69. 2. Dudley GA, Djmil R: Incomptibility of endurnce- nd strength-trining modes of exercise. J Appl Physiol 1985; 59: 1446 51. 3. Sle DG, Jcobs I, McDougll JD, Grner S: Comprison of two regimens of concurrent strength nd endurnce trining. Med Sci Sports Exerc 1990; 22: 348 56. 4. Bell GJ, Syrotuik D, Mrtin TP, Burnhm R, Quinney HA: Effect of concurrent strength nd endurnce trining on skeletl muscle properties nd hormone
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