Physical Fitness and Physical Training during Norwegian Military Service

Transcription

1 MILITARY MEDICINE, 171, 8:736, 2006 Physicl Fitness nd Physicl Trining during Norwegin Militry Service Gurntor: Sindre M. Dyrstd, PhD Contributors: Sindre M. Dyrstd, PhD* ; Rune Soltvedt, MSc*; Jostein Hllén, PhD* Objective: Evlute the physicl fitness nd trining of Norwegin infntry soldiers during 10 months of compulsory militry service. Methods: Mximl oxygen uptke (V O 2 mx) nd mximl numbers of sit-ups, push-ups, nd chin-ups nd 3-km running time were tested in 107 mle infntry soldiers t the beginning nd end of bsic trining (BT), nd gin t demobiliztion. The mount of physicl trining ws registered throughout the militry service. Results: During BT, mjor improvements in sit-ups nd push-ups were found. V O 2 mx incresed in soldiers with the lowest initil V O 2 mx, but decresed to pre-bt level t demobiliztion. The mount of obligtory physicl trining ws 8.5 hours week 1 during BT nd 35% lower fter BT, nd ws usully performed in uniform t low to moderte intensity. Conclusion: The mount of highintensity endurnce nd strength trining during compulsory militry service is to low to improve the soldiers endurnce nd musculr strength. Introduction orwegin men perform 1 yer of compulsory militry service. Since the V O 2 mx of young Norwegin men hs de- N cresed by 8% during the pst 20 yers, 1 it is importnt tht the physicl trining during the militry service is of such stndrd tht the soldiers become qulified for tsks tht demnd good physicl fitness. During the bsic trining (BT) period, the first 2 to 3 months of militry service, soldiers prticipte in bsic militry lessons nd physicl trining. Some studies hve found tht the soldiers V O 2 mx increses during BT, 2 5 wheres other studies hve found no chnges 6 8 or even reduction. 9 In some studies, lck of improvement in V O 2 mx during BT is explined by high initil erobic fitness. 6,10 12 Mrcinik et l. 7 lso emphsize tht the ttitudes of compny commnders towrd exercise, prticiption in scheduled exercise sessions, nd overll ledership style ffect the finl fitness outcomes. However, the most importnt fctors for improvement in physicl fitness re trining volume, frequency, intensity nd mode of trining. The Norwegin Defense generl regultions stte tht ll soldiers shll complete t lest 2 hours of physicl trining per week in t lest two sessions. 13 The infntry eductionl progrm sttes tht during BT, 4 hours of physicl trining per week shll be completed nd tht the soldiers should be encourged to do dditionl trining during leisure time. However, prestudy interviews with the present militry unit suggested tht ctul physicl trining ws less thn tht required by regultions. The ims of this study were to (1) evlute the effect of two trining lods on physicl fitness of Norwegin infntry soldiers *Norwegin School of Sport Sciences, P.O. Box 4014 Ullevl Stdion, N-0806, Oslo, Norwy. Defense Institute, Norwegin School of Sport Sciences, Oslo, Norwy. This mnuscript ws received for review in Mrch 2005 nd ws ccepted for publiction in My Reprint & Copyright by Assocition of Militry Surgeons of U.S., nd (2) document the mount of strenuous physicl ctivity completed during Norwegin compulsory militry service. Methods Subjects Four pltoons from two compnies, totl of 148 Norwegin infntry soldiers, were selected for the study. All soldiers followed the sme eductionl progrm during the compulsory militry service. After exclusion due to illness, injury, nd leve of bsence, 107 soldiers, 19.2 (0.8) yers of ge, were included in the pre- nd post-bt tests. Trnsfer to other units resulted in dropout of n dditionl 23 soldiers before the test t demobiliztion. There were no differences in V O 2 mx, body weight, nd height between the dropouts nd the remining subjects. The study ws pproved by the regionl ethics committee, nd written informed consent ws obtined from the soldiers. Study Design Two pltoons ech were ssigned to n intervention nd control group during BT. The control group followed the obligtory trining progrm set up by the compny leders. This progrm included 1 hour of strength trining nd 1 hour of endurnce trining in two different trining sessions ech week. To evlute the effect of incresed trining lod, the intervention group ws instructed to double this mount, divided in four trining sessions ech week. The officers in the intervention group ttended course which gve prcticl nd theoreticl lessons in physicl trining. After BT, ll pltoons followed the obligtory trining determined by the compny leders. The mount of strenuous physicl ctivity, performed in uniform or swetsuit, ws registered throughout the service. V O 2 mx, time to exhustion (TTE), nd the mximl numbers of push-ups, sit-ups, nd chin-ups were tested t the beginning (pre-bt) nd the end (post-bt) of the 10-week BT period, nd gin before demobiliztion, 10 months fter entry. The 3-km running time ws evluted pre-bt nd t demobiliztion. One pltoon in the intervention group did not complete the tests of strength nd musculr endurnce in the post-bt test. However, the two pltoons in the intervention group hd the sme mount of trining nd there ws no difference in the pre-bt test results. Mesurements Mximl O 2 Uptke nd TTE V O 2 mx nd TTE were ssessed by tredmill running using stepwise incrementl protocol with constnt incline of 5.2% nd speed increment of 1 km h 1 every minute until exhustion. The initil speed for ech individul ws chosen ccording to pretest fmiliriztion tril to ensure tht the continuous exer- Militry Medicine, Vol. 171, August

2 Fitness nd Trining during Norwegin Militry Service cising phse would lst 4 to 7 minutes. The subjects were encourged to run s long s possible nd TTE ws mesured. Before the test, subjects wrmed up with 20 minutes of running followed by 5 minutes of rest. Subjects wore nose clip nd were connected to the oxygen mesuring system (Oxycon Pro, Erich Jeger, Hoechberg, Germny) vi mouthpiece nd three-wy directionl vlve (Hns Rudolf, Inc., Knss City, Missouri). The Oxycon Pro ws clibrted with room ir nd certified clibrtion gses t 180 kp (5.55% CO 2 nd 94.45% N 2 ). Adequte ventiltion ensured tht gs concentrtions in the lbortory were the sme s outdoors. The volume sensor (Triple V, Erich Jeger) ws utomticlly flowclibrted ccording to the mnul. Hert rte (HR) ws continuously mesured with HR monitor (Polr Pcer, Polr Electro Oy, Kempele, Finlnd) nd the highest HR during the test ws defined s pek HR. A blood smple ws tken from fingertip 3 minutes fter exercise nd nlyzed by n enzymtic method for lctte concentrtion. The lctte nlyzer (YSI 1500 Sport, YSI Inc., Yellow Springs, Ohio) ws clibrted with 5 mmol l 1 lctte stndrd nd linerity ws controlled with 15 mmol l 1 lctte stndrd. Clibrtion ws ccepted when low nd high vlues were in the rnge of 4.9 to 5.1 mmol l 1 nd 14.0 to 15.7 mmol l 1, respectively. Volitionl exhustion ws the min criterion indicting tht V O 2 mx ws chieved, nd the highest men V O 2 over 1 minute ws set s V O 2 mx. In cses where the subject s exhustion ws in doubt, the following set of criteri were used to indicte exhustion: (1) respirtory exchnge rtio (RER) bove 1.05, (2) blood lctte (bl ) bove 6 mmol l 1, nd 3) test durtion longer thn 4 minutes. For the post-bt nd demobiliztion tests, the pek HR ws evluted ginst the pek HR chieved in the previous test. Body weight ws mesured using digitl scle (model 708, Sec Corp., Hmburg, Germny) with subjects wering T-shirts, shorts, nd socks. Height ws mesured using stdiometer (model 708, Sec Corp.). Stndrd Militry Tests The 3-km running time ws used s mesure of erobic endurnce. This test ws performed outdoors in consistent wether conditions on level, pved surfce. Sit-ups were used s mesure of musculr endurnce of the trunk nd hip flexors. The strting position ws supine position with legs t box horse, 90 degrees t the knees nd held by prtner. The upper body ws rised in such wy tht the elbow touched the opposite knee. Push-ups were used s mesure of musculr endurnce of the rm, shoulder, nd chest. Subjects begn with stright body nd the chest nd cheek touching the floor. The upper body ws rised until the rms were stright. Chin-ups were used s mesure of rm nd shoulder strength. The strting position ws hnging freely from br using n overhnd grsp nd with stright rms nd legs. The chin ws pulled over the br. Mximl numbers of repetitions for sit-ups, push-ups, nd chin-ups were counted. Physicl Trining Registrtion During BT, ll 148 soldiers reported their performed strenuous physicl ctivity on weekly report form. Activities to be included were obligtory physicl trining in swetsuit, optionl physicl trining during leisure time, nd strenuous physicl ctivity in uniform lsting 20 minutes. Typicl intervl ctivities lsting 20 minutes were lso included. Trining intensity ws ctegorized s low, medium, or hrd. The men weekly response rte ws 79% for the intervention group nd 69% for the control group. After BT, one officer in ech pltoon reported the pltoon s performed obligtory physicl trining nd strenuous physicl militry ctivity, which minly consisted of mrching with bckpck, bttle trining, nd different types of movement in rugged terrin. Optionl physicl trining ws not reported during the finl 6 months. To evlute the trining intensity during dys with strenuous militry ctivity in uniform, 17 soldiers were equipped with HR recorder nd receiver (Polr s610, Polr Electro Oy). Performed ctivity lsting 20 minutes with n intensity of minimum 60% of pek HR nd ctivity lsting 3 minutes t minimum 80% of pek HR were counted s trining. Severl times week, the soldiers performed hrd 45-minute uphill mrch to the shooting rnge, nd the intensity ws ssessed using HR recordings in 11 rndomly selected soldiers. Sttisticl Anlysis nd Dt Processing The Student s t test ws used to compre mens between two smples for given vrible. One-wy nlysis of vrince with Tukey s post hoc tests were used to exmine the significnce of differences between more thn two smples. A multivrite test for repeted mesurements ws performed before other nlyses of the test dt. A p 0.05 ws regrded s sttisticlly significnt, nd p vlue between 0.05 nd 0.1 ws set to indicte tendency. Results re presented s men SD, or s men stndrd error of the men (SEM). SD is used if not otherwise is written. Since there ws no difference in the V O 2 mx before BT between the intervention nd control groups, nd no significnt difference in the chnges in V O 2 mx during the BT period, the two groups were merged where pproprite. The subjects were subdivided into three equl-sized groups ccording to their initil V O 2 mx (low, medium, nd high). This vlue ws compred to the chnge in V O 2 mx from the pre-bt test to post-bt test. When the difference between the two vribles is compred to one of these vribles, there will be built-in correltion where 0.7. r 2 2 To conclude tht there is significnt correltion between these vribles, the r vlue must differ from 0.7. In this cse the t vlue ws 2.56, mening tht the p vlue ws Results 737 The weekly obligtory trining for the intervention group during BT ws 73 (26) minutes, nd consisted of n verge 30 minutes of running, 31 minutes strength trining, nd 12 minutes of other ctivities, minly bll ply (Tble I). Weekly obligtory trining for the control group ws 20 (19) minutes nd consisted primrily of strength trining. The intervention group s weekly optionl trining consisted of n verge 16 minutes of strength trining nd 16 minutes of other ctivities, minly bll ply. The control group s weekly optionl trining Militry Medicine, Vol. 171, August 2006

3 738 Fitness nd Trining during Norwegin Militry Service TABLE I AVERAGE WEEKLY PHYSICAL TRAINING VOLUME THROUGH THE 10 WEEKS OF BASIC TRAINING, MEAN (SD) Physicl Trining Volume Intervention Group (n 71) Control Group (n 77) All (n 148) Obligtory (min week 1 ) 73 (26) 21 (20) 46 (35) Obligtory (sessions week 1 ) 1.7 (0.5) 0.4 (0.3) 1.0 (0.8) Optionl (min week 1 ) 32 (36) 66 (91) 49 (72) Optionl (sessions week 1 ) 0.5 (0.6) 1.0 (1.2) 0.8 (1.0) In uniform (min week 1 ) 401 (170) 521 (362) b 462 (290) In uniform (sessions week 1 ) 2.2 (0.6) 2.4 (1.1) 2.3 (0.9) Different from the intervention group, p b Different from the intervention group, p consisted of n verge 45 minutes of strength trining nd 21 minutes of other ctivities, minly bll ply. Approximtely 60% of ll soldiers completed less thn 30 minutes of optionl exercise weekly, while 12% completed more thn 2 hours of optionl exercise weekly. On dys with 6 to 8 hours of strenuous physicl ctivity in uniform, the verge HR during ctivity ws 113 (8) bets min 1, equivlent to 58% (5%) of pek HR (n 17). Distribution of physicl ctivity with n intensity of minimum 60% of pek HR is shown in Figure 1. Forty-one percent of the soldiers hd no periods with HR bove 80% of pek HR for t lest 3 minutes continuously, while 35% of the soldiers hd 15 minutes of such ctivity. During the 45-minute mrch to the shooting rnge, the men HR ws 142 (8) bets min 1, corresponding to 74% (6%) of pek HR (n 11). The 50% of soldiers who worked t the lowest percentge of pek HR during this mrch tended to hve n 8% higher V O 2 mx compred with the 50% who worked t the highest percentge of pek HR (p 0.09). After BT, the totl mount of obligtory physicl ctivity decresed by 35% to 5.4 (3.5) hours week 1, including 3.8 (3.1) hours week 1 of strenuous physicl ctivity in uniform. There ws on verge 95 (77) min week 1 of obligtory physicl trining in swetsuits during the finl 6 months of service. This trining consisted of 54 (40) min week 1 strength trining nd 40 (41) min week 1 endurnce trining. Fig. 1. Percent distribution of physicl ctivity with n intensity of minimum 60% of pek HR during strenuous dy with militry ctivity in uniform, n 17. During BT, V O 2 mx nd TTE of the intervention group incresed by 2.5% (0.9%) nd 7.7% (1.7%) (SEM; p 0.05), respectively, with no chnges in the control group (Tble II). Before BT, the verge vlues of bl, pek HR, nd RER for ll subjects were 9.0 (1.9) mmol l 1, 197 (9) bets min 1 nd 1.13 (0.07), respectively. Looking t the chnge in V O 2 mx ccording to initil V O 2 mx, we found tht the group with the lowest initil V O 2 mx (49.4 (2.8) ml kg 1 min 1 ) hd 5.0% (1.0%) increse (SEM; p 0.001) in V O 2 mx during BT. For the medium initil V O 2 mx group (54.6 (1.5) ml kg 1 min 1 ), no chnge ws found, nd for the high initil V O 2 mx group (59.7 (2.5) ml kg 1 min 1 ), V O 2 mx tended to decrese by 1.1% (0.6%) (SEM; p 0.07). For the 12 soldiers with V O 2 mx higher thn 60 ml kg 1 min 1, V O 2 mx decresed by 3% during BT (p 0.01, Fig. 2). For the 84 soldiers (ge 19.1 (0.8) yers) who were tested t demobiliztion, V O 2 mx in ml kg 1 min 1 decresed by 2.5% (0.5%) nd body weight incresed by 4.0% (0.4%) (SEM; p 0.001) compred with the post-bt results. TTE followed the sme pttern s V O 2 mx (Tble III). A comprison of the low, medium, nd high initil V O 2 mx groups showed tht ll three groups experienced reduction in V O 2 mx fter BT (Tble IV). There were no differences in pek HR, bl nd RER between the post-bt test nd the test t demobiliztion. During BT, there were no differences between the control (n 48) nd the intervention (n 26) groups in sit-up performnce; when merged, both groups incresed from 29 (10) to 45 (21) repetitions (p 0.01). The intervention nd control groups incresed push-up performnce from 25 (12) to 29 (9) nd 27 (9) to 36 (10) repetitions, respectively (p 0.05). There ws no chnge in chin-ups. Through the rest of the compulsory service, the repetitions of push-ups showed minor increse, while there were no significnt chnges in sit-ups nd chin-ups. The 3-km running time improved by 5.7% (1.0%) from entry to demobiliztion (SEM; p 0.01, Tble V). Discussion The soldiers completed pproximtely 9 hours of strenuous physicl ctivity per week during BT, mostly in uniform t low to moderte intensity. V O 2 mx incresed for the soldiers with the lowest initil V O 2 mx only. After BT, the obiligtory physicl ctivity decresed by 35% nd both V O 2 mx nd TTE decresed independent of initil V O 2 mx. Improvement in sit-ups nd push-ups leveled off fter BT, while there ws no chnge in chin-ups during the service. To increse physicl fitness of ll Militry Medicine, Vol. 171, August 2006

4 Fitness nd Trining during Norwegin Militry Service 739 TABLE II VO 2 MAX, TTE, BODY WEIGHT, AND BODY HEIGHT AT ENTRY AND AFTER 10 WEEKS OF BASIC TRAINING, MEAN (SD) Intervention Group (n 56) Control Group (n 51) At entry After 10 weeks At entry After 10 weeks VO 2 mx (ml kg 1 min 1 ) 53.9 (5.2) 55.1 (4.6) 55.4 (4.3) 55.6 (3.7) VO 2 mx (l min 1 ) 4.11 (0.47) 4.22 (0.48) b 4.10 (0.44) 4.18 (0.41) b TTE (min) 5.51 (0.62) 5.91 (0.79) 5.39 (0.53) 5.45 (0.70) Body weight (kg) 76.8 (10.5) 76.9 (8.8) 74.2 (6.9) 75.2 (6.3) b Body height (cm) (6.4) (5.7) b Different from previous test, p Fig. 2. Reltionship between V O 2 mx t entry nd chnge in V O 2 mx fter 10 weeks of bsic trining (n 107, R 0.49, p 0.05). soldiers during militry service, more of the physicl trining should be orgnized in short, more intensive trining sessions. During BT, the soldiers with the lowest initil V O 2 mx incresed their V O 2 mx by 5%, due to 2% decrese in body weight, nd 4% increse in V O 2 mx (ml min 1 ). The soldiers with the highest initil V O 2 mx tended to experience decrese in V O 2 mx due to 2% increse in body weight. This is in line with other studies tht hve concluded tht BT increses V O 2 mx only in the lest fit soldiers. 4,5,9,11,14 During BT, the totl volume of weekly physicl trining ws 9.2 (4.9) h, nd 84% of this ctivity ws conducted in uniform, mostly t low intensity. The control group hd on verge less thn one trining session in swetsuits every second week. According to the eductionl progrm, this is 20% of the prescribed mount. The intervention group performed 43% of the scheduled trining progrm of 4 trining sessions per week. A busy eductionl progrm combined with low priority for physicl trining ws, ccording to the officers, the reson for the low mount of physicl trining in swetsuits. To rech the gol of four trining sessions per week, these sessions must be scheduled into the weekly eductionl progrm nd prioritized s highly s other militry lessons. Differentition of trining intensity is often difficult during militry service. During physiclly demnding tsks when soldiers operte in squds or troops, the soldiers with the lowest erobic fitness nd strength determine the exercise intensity for the group. We found tht during strenuous militry ctivities, one-third of the soldiers hd no periods lsting 20 minutes bove 60% of pek HR. Hence, the trining stimuli during militry ctivities were insufficient to improve the V O 2 mx in soldiers with verge or bove verge V O 2 mx. For the lest fit soldiers, mny militry ctivities were crried out t trining intensities sufficient to improve V O 2 mx. Unlike the control group, the intervention group in verge improved both V O 2 mx nd TTE during BT, despite the fct tht the control group reported more of both optionl trining nd totl militry ctivity. However, the mount of high-intensity ctivity in uniform ws not different between the groups, nd the optionl trining consisted mostly of strength trining. The min difference between the groups ws 30 to 40 minutes per week of obligtory, medium- to high-intensity endurnce trining in the intervention group. This my explin the improvement seen in the intervention group, especilly in the lest fit soldiers. In mny studies, physicl trining during BT is poorly described, lthough some uthors hve indicted BT to consist of 4 to 6 hours per week of trining, including physicl trining in uniform nd excluding optionl exercise. 4,14,15 This is comprble to the mount of performed trining fter BT in the present study. For young, not-endurnce-trined men, the volume of trining performed during BT would normlly improve the V O 2 mx more thn ws found in this study, especilly in the lest fit group. In different trining studies, the improvement in V O 2 mx rnged from 10% to 30%, depending upon the qulity nd quntity of trining. 16 Higher intensity trining is consistently found to elicit greter increses in V O 2 mx thn lower intensity trining of longer durtion. 17 Oj 18 concluded tht the intensity of physicl ctivity my be stronger dose chrcteristic thn the totl volume of ctivity for fitness response, in line with severl other review studies Generlly, exercise t 70% of mx HR is sufficient to improve erobic fitness for previously sedentry persons. 22 During this study, however, mny soldiers did not rech this intensity over sufficient period of time. Mles et l. 23 showed tht trining progrm of 4 45 minutes of high intensity trining ws much more effective thn 2 90 minutes of lower intensity for improving strength nd endurnce in Crotin soldiers. The soldiers in the present study hve high volume of low-intensity trining. By introducing shorter trining sessions crried out t high intensity, n verge improvement in V O 2 mx between 5% nd 10% should be relistic. After BT, more militry opertions nd bttle exercises were crried out nd the weekly obligtory physicl ctivity decresed by 35%. This resulted in lower V O 2 mx t demobiliztion thn t entry. The improvements in V O 2 mx obtined by the lest fit soldiers during BT were lso lost during the lst 6 months of Militry Medicine, Vol. 171, August 2006

5 740 Fitness nd Trining during Norwegin Militry Service TABLE III VO 2 MAX, TTE, BODY WEIGHT, AND HEIGHT AT ENTRY, AFTER BASIC TRAINING 10 WEEKS AFTER ENTRY, AND AT DEMOBILIZATION 10 MONTHS AFTER ENTRY, MEAN (SD) n At Entry After 10 Weeks After 10 Months VO 2 mx (ml kg 1 min 1 ) (4.8) 55.5 (4.2) 54.1 (4.4) VO 2 mx (l min 1 ) (0.46) 4.24 (0.46) 4.29 (0.46) TTE (min) (0.56) 5.72 (0.75) 5.49 (0.71) Body weight (kg) (9.2) 76.5 (7.8) 79.5 (8.2) Body height (cm) (6.1) (6.1) TABLE IV VO 2 MAX OF THE SOLDIERS, SUBDIVIDED INTO GROUPS ACCORDING TO INITIAL VO 2 MAX, AT ENTRY, AFTER BASIC TRAINING, 10 WEEKS AFTER ENTRY, AND AT DEMOBILIZATION 10 MONTHS AFTER ENTRY, MEAN (SD) At Entry After 10 Weeks After 10 Months n VO 2 mx (ml kg 1 min 1 ) Highest initil VO 2 mx (2.1) 59.1 (2.6) 58.0 (3.1) Medium initil VO 2 mx (1.3) 55.3 (2.9) 53.9 (3.0) Lowest initil VO 2 mx (2.8) 52.2 (3.8) 50.4 (3.2) TABLE V THE 3-KM RUNNING TIME (MIN), MEAN NUMBER OF REPETITIONS FOR SIT-UPS, PUSH-UPS, AND CHIN-UPS AT ENTRY, AFTER BASIC TRAINING, 10 WEEKS AFTER ENTRY, AND AT DEMOBILIZATION 10 MONTHS AFTER ENTRY, MEAN (SD) Exercise Vrible n At Entry After 10 Weeks After 10 Months 3-km run (1.90) (1.14) Sit-ups (9) 45 (22) 49 (29) Push-ups (10) 32 (11) 34 (11) b Chin-ups (3.9) 5.4 (3.3) 5.6 (3.4) Different from previous test, p b service. Studies hve shown tht reductions in trining frequency up to 50% nd 60% to 70% reduction in trining durtion do not reduce V O 2 mx s long s the trining intensity is mintined. 20,24 Thus, when the militry service includes reduced mount of physicl trining, high trining intensity cn void decrese of V O 2 mx. Interestingly, 3-km running performnce improved by 7% during the compulsory service. Improved running tctics resulting in more optiml energy use during the test is probbly of significnt importnce. In ddition, the high volume of lowintensity trining my hve resulted in higher musculr endurnce. Lrger improvements in vrious endurnce tests compred with V O 2 mx tests hve lso been found in other studies of militry personnel, 6,8,14 indicting tht V O 2 mx is not the only fctor tht ffects endurnce cpcity. It seems tht the objective of the physicl trining during BT in mny countries is to trin the lest fit soldiers to good stndrd of erobic fitness. This objective is essentil to ensure tht physicl cpcity does not become limiting fctor in militry opertions. Furthermore, untrined soldiers re found to hve 4-fold higher injury rte compred with well-trined soldiers. 25 However, vrying trining intensities, ccounting for individul fitness level, would increse the likelihood of improving the fitness of ll soldiers, regrdless of initil fitness level. The dvntges of differentiting the trining progrm to improve the performnce in lod crrige tsk were recently shown in the work of Willims et l. 26 Significnt improvements in push-ups nd sit-ups tests were found, with most of the improvement occurring during BT. Activities like mrching with hevy bckpck nd other obligtory nd optionl strength trining my hve cused these improvements. After BT, the improvements leveled off, most likely becuse of n insufficient trining progression. No improvement in chin-ups ws seen during the service. This ws surprising since strength trining ws the most populr ctivity during optionl trining. However, chin-ups were rrely performed during the dily militry service, nd exercises stimulting the chest, such s bench press, were preferred during strength trining. Trining regimes with high number of repetitions were lso often used. To elicit improvements in both musculr strength nd endurnce, most experts recommend 8 to 12 repetitions per set, lthough lower repetition rnge (e.g., 6 to 8 repetitions) with hevier weights my better optimize strength nd power development. 27 Fff et l. 8 found n increse in both sit-ups (21%) nd chin-ups (42%), while Willims et l. 15 found n improvement in musculr endurnce but no improvement in musculr strength during BT, in greement with the present study. Militry Medicine, Vol. 171, August 2006

6 Fitness nd Trining during Norwegin Militry Service Conclusion During BT, the totl mount of obligtory physicl trining ws 8.5 (4.7) hours per week, nd this mount decresed by 35% fter BT. Between 70% nd 85% of this trining ws conducted in uniform t low to moderte intensity. During BT, the V O 2 mx incresed by 5% for the subjects with the lowest initil V O 2 mx, no chnge ws seen in the subjects with medium initil V O 2 mx, while V O 2 mx in the subjects with the highest initil level tended to decrese. After BT, V O 2mx decresed in ll soldiers, independent of the initil V O 2 mx. Since longer exercise durtion usully implies lower exercise intensity, the continuous militry ctivity in the present study seemed to be n indequte trining stimulus for incresing V O 2 mx, except in the lest fit soldiers during BT. Most of the increse in sit-ups nd push-ups performnce occurred during BT. No improvement in chin-ups ws found. Higher nd more differentited trining intensities s well s regulr strength nd endurnce trining could improve the trining effect for ll soldiers, especilly fter BT. Acknowledgments We thnk Professor Sigmund B. Strømme for useful comments on the rticle. We lso cknowledge Cptin Stig Hjellset nd Anders Andstd for help with the dt collection nd Jennifer Arnesen for English revision. This study ws funded by the Norwegin School of Sport Sciences/ Defense Institute. References 1. Dyrstd S, Andstd A, Hllen J: Aerobic fitness in young Norwegin men; comprison between 1980 nd Scnd J Med Sci Sports 2005; 15: Kowl DM, Ptton JF, Vogel JA: Psychologicl sttes nd erobic fitness of mle nd femle recruits before nd fter bsic trining. Avit Spce Environ Med 1978; 49: Vogel JA, Crowdy JP, Amor AF, Worsley DE: Chnges in erobic fitness nd body ft during rmy recruit trining. Eur J Appl Physiol Occup Physiol 1978; 40: Ptton JF, Dniels WL, Vogel JA: Aerobic power nd body ft of men nd women during rmy bsic trining. 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