Ambulatory Physical Activity in Swiss Army Recruits

Transcription

1 716 Training & Tsting Amulatory Physical Activity in Swiss Army Rcruits Authors Affiliation T. Wyss, J. Schfflr, U. Mädr Swiss Fdral Institut of Sports Magglingn SFISM, Sport and Prformanc Unit, Magglingn, Switzrland Ky words nrgy xpnditur walking distanc ody-waral snsors physical rquirmnts physical dmands military occupational spcialtis accptd aftr rvision Octor 18, 2011 Biliography DOI /s Pulishd onlin: Jun 15, 2012 Int J Sports Md 2012; 33: Gorg Thim Vrlag KG Stuttgart Nw York ISSN Corrspondnc Dr. Thomas Wyss Swiss Fdral Institut of Sports Magglingn SFISM Fdral offfic of Sport FOSPO 2532 Magglingn Switzrland Tl.: +41/32/ Fax: +41/32/ thomas.wyss@aspo.admin.ch Astract Th aim of this study was to ojctivly assss and compar th typ, duration and intnsity of physical activity during th asic training providd y ach of 5 slctd Swiss Army occupational spcialtis. Th first ojctiv was to dvlop and validat a mthod to assss distanc covrd on foot. Th scond ojctiv was to dscri and compar physical activity lvls among occupational spcialtis. In th first part of th study, 30 mal voluntrs compltd 6 laps of 290 m at diffrnt gait vlocitis. Data from 15 voluntrs wr usd to dvlop linar rgrssion quations for th rlationship twn stp frquncy and gait vlocity, and data from th othr 15 voluntrs wr usd to vrify th accuracy of ths quations. In th scond part of th study, 250 voluntrs from 5 military schools (ach training school for a diffrnt occupational spcialty) wor hart-rat, acclration and stp-count monitors during workdays of wks 2, 4, 8 and 10 of thir asic training. Snsor data wr usd to idntify physically dmanding activitis, stimat nrgy xpnditur (asd on alrady pulishd algorithms) and stimat distanc covrd Introduction To assss th physical jo rquirmnts of military occupations, prior studis hav attmptd to idntify ithr th typ of th most frquntly prformd physically dmanding activity or th intnsity of daily physical activity. Th most frquntly prformd physically dmanding activitis wr invstigatd using slf-rport qustionnairs [12, 17 ]. Rayson [17 ] showd that 89 % of physically dmanding tasks in British Army occupations involvd ithr lifting or carrying loads. Walking, marching with a ackpack, running and physically dmanding matrials-handling (including lifting and lowring loads, lifting and carry- on foot (asd on th algorithm dvlopd in th first part of this study). A ranchd modl using 2 rgrssion quations (gait vlocity = stp frquncy for walking spds low 1 m/s and gait vlocity = stp frquncy for fastr gait vlocitis) was shown to accurat for stimating distanc covrd on foot. In th training schools invstigatd, avrag physical activity nrgy xpnditur was 10.5 ± 2.4 MJ pr day, and trains covrd 12.9 ± 3.3 km pr day on foot. Rcruits spnt 61.0 ± 23.3 min pr day marching and 33.1 ± 19.5 min pr day prforming physically dmanding matrials-handling activitis. Avrag physical activity nrgy xpnditur dcrasd significantly from wk 2 to wk 8. Th masurmnt systm utilisd in th prsnt study yildd data comparal to thos of prior studis that applid altrnativ mthods. Nvrthlss, th nw snsor-asd, ojctiv masurmnt systm usd providd mor information on daily physical activity and dmands than traditional, singl masurmnt instrumnts. Th avrag daily total nrgy xpnditur valus in all training schools invstigatd wr within th rang found for th armd forcs of othr nations and for profssional athlts. ing loads, and digging) wr idntifid as th ky common tasks prformd in rcnt and currnt military missions of th North Atlantic Traty Organization (NATO) [12 ]. Th intnsity of daily physical activity was invstigatd y stimation of nrgy xpnditur using th douly lalld watr (DLW) mthod [5, 10, 21, 22, 25 ] or y stimation of distanc covrd on foot using pdomtrs [14 ]. Th total nrgy xpnditur (TEE) assssd during th daily military routin rangd from 14.1 MJ/d for US support soldirs to 17.2 MJ/d for US Spcial Forcs [21 ]. In thir mta-analysis, Tharion t al. [ 22 ] summarisd TEE valus as MJ/d during asic training (BT), which is comparal in duration to that Wyss T t al. Amulatory Physical Activity in Int J Sports Md 2012; 33:

2 Training & Tsting 717 of th Swiss Army. Howvr, ojctivly dtrmind valus for typ, duration and intnsity of military-spcific activitis hav not yt n assssd to quantify jo rquirmnts in Swiss Army occupational spcialtis. Th aim of th prsnt study was to quantify th typ, intnsity and duration of physical activity during th BT of 5 slctd Swiss Army occupational spcialtis. Rcntly pulishd ojctiv masurmnt mthods wr applid [27, 28 ] ; ths allow for th rcognition of military-spcific activitis and th stimation of nrgy xpnditur during daily military routins using ody-fixd acclromtr and hart-rat monitors. Th GT1M acclromtr (ActiGraph LLC, Fort Walton Bach, FL), was usd to rcord sujcts hip acclrations and stp frquncy (SF). Sinc SF is linarly rlatd to gait vlocity (GV) ovr a larg rang of walking spds [6, 7, 18, 20 ], a scond aim of th prsnt study was to dfin an algorithm to calculat a sujct s daily distanc covrd on foot asd on SF rcordd at 0.5 Hz. Matrials and Mthods Participants and masurmnt protocol Linar rgrssion twn SF and GV In th first part of th study, to stimat th multipl linar rgrssion quation twn ody hight, SF and GV in young mn, 30 halthy mal voluntrs (ag rang yars) wr rcruitd from studnts of th Swiss Fdral Institut of Sports, Magglingn. Sinc prvious studis hav shown that ody wight has no influnc on th rlationship twn SF and GV, only ody hight was masurd and includd in rgrssion modls [19, 26 ]. Th voluntrs compltd 6 laps of 290 m ach on a lvl floor whil waring a GT1M on th hip. At th start of ach lap, participants wr vrally instructd to walk at a givn spd. Th spd was prscrid in road catgoris and incrasd from a vry slow walk (stroll) in th first lap to aroic running (at th individual s prfrrd running spd) in th last lap. 15 randomly chosn voluntrs wr allocatd to th training-data group, and th othr 15 to th control-data group. Data from th training-data group wr usd to dvlop th linar rgrssion quations for ody hight and SF as indpndnt varials, and GV as a dpndnt varial. Data from th controldata group wr usd to vrify th accuracy of th dvlopd GV stimation algorithm. Amulatory physical activitis during Swiss Army BT In th main part of this study, to assss amulatory physical activity during Swiss Army BT, 5 occupational spcialtis wr invstigatd. 4 Swiss Army training schools (rscu tchnician, armourd infantry, fusilir infantry and rconnaissanc infantry) wr chosn to mt th critrion of ing physically dmanding, asd on xprt appraisal. Furthr, th communications intllignc training school was chosn to rprsnt th lss physically dmanding occupational spcialtis. In all ths occupational spcialtis, BT consistd of a gnral asic training (GBT) for th first 7 wks and a functional asic training (FBT) for th susqunt 6 wks. Th dsignatd GBT contnt was similar for all occupational spcialtis: approximatly 1 day in a classroom and 4 days in th fild, with 180 min of physical training pr wk, and a focus on larning asic military skills. Howvr, appraisals of popl involvd indicatd that th physical activity and physical training in diffrnt attalions may diffr sustantially, dpnding on th prioritis st y ach commandr. During FBT, rcruits larn spcific skills ndd in thir ranch of th armd forcs. In this part of BT th physical tasks diffr twn occupational spcialtis. Rscu tchnicians focus on working on sit with havy quipmnt, rconnaissanc rcruits focus on walking long distancs, armourd and fusilir infantry focus on various physically dmanding fild tasks, whras communications intllignc rcruits hav no spcific physical tasks. All mal rcruits at th 5 training schools wr askd to voluntr for th study. Of ths voluntrs, 50 sujcts wr randomly chosn from ach school to participat. Participants rcivd comprhnsiv information on th study, and ach providd writtn informd consnt for participation, as approvd y th Cantonal Ethics Committ of Brn, Switzrland. Th study was prformd in accordanc with th thical standards for sport and xrcis scinc rsarch [ 11 ]. Each participant s hight, wight and ag wr assssd at th start of BT. Ag was rcordd as th diffrnc twn dat of irth and dat of starting BT. Participants wr askd to war a hart-rat monitor on th chst, a GT1M on th hip and anothr GT1M on th ackpack during ach day of wks 2, 4, 8 and 10 of thir military BT. Wks 2 and 4 rprsntd GBT, and wks 8 and 10 rprsntd FBT. Body-fixd snsors had to worn from th tim participants wok in th morning until thy wnt to d in th vning. Sinc th majority of trains in Swiss Army BT do not srv at wknds, only Mondays to Fridays wr includd in th invstigation. Snsors wr thrfor distriutd on Sunday vnings and collctd on th following Saturday morning. Instrumnts Body hight was masurd to th narst 0.1 cm using a stadiomtr (Sca modl 214, Sca GmH, Hamurg, Grmany), and ody wight was masurd to th narst 0.1 kg on a caliratd digital alanc (Sca modl 877, Sca GmH, Hamurg, Grmany). A hart-rat monitor (Suunto Smartlt, Suunto, Fantaa, Finland), and a GT1M comind stp and acclration monitor wr usd to rgistr data for physical activity-rlatd paramtrs. GT1Ms wr wrappd in watrproof plastic and placd in lt pouchs worn on th waist aov th right antrior axillary lin, and on th sid strap of th prsonal ackpack. Th snsors wr programmd to stor hart-rat, hip-acclration, stpcount and ackpack-acclration data at 2-s intrvals. Data procssing and statistical analysis Statistical analyss wr prformd using SPSS for Windows (vrsion 16.0, SPSS Inc., Chicago, IL) with an alpha lvl of 0.05 to indicat statistical significanc. Group rsults ar prsntd as man ± standard dviation. Linar rgrssion twn SF and GV To driv GV and SF, th distanc (290 m) and th masurd numr of stps wr dividd y th tim takn pr lap. Data from th training-data group wr usd to calculat a multipl linar rgrssion quation using ody hight and SF as indpndnt varials and GV as th dpndnt varial. This rgrssion quation and that of Trrir and Schutz [ 20 ] wr applid concurrntly to data from th control-data group. For approximatly normally distriutd data, a paird t-tst was conductd to dtct statistical diffrncs twn stimatd and masurd GV valus. Errors of stimatd GV wr quantifid with a 95 % confidnc intrval of diffrncs (CI-95 %). Furthr, Parson s corrlation tsts and Bland-Altman plots wr pr- Wyss T t al. Amulatory Physical Activity in Int J Sports Md 2012; 33:

3 718 Training & Tsting formd twn stimatd and masurd GV. Using GV, th distanc covrd during ach 2 s tim intrval was calculatd. Th sum of distancs calculatd for all invstigatd tim intrvals pr day rprsntd th daily distanc covrd on foot. Amulatory physical activitis during Swiss Army BT Data from thos voluntrs who providd ovr 480 min of snsor signals pr day wr includd in th analyss. For ach invstigatd day of BT, th mdian of distanc covrd on foot, minuts spnt in military-spcific activity classs or in othr activitis, intnsity lvl and physical activity nrgy xpnditur (PAEE) wr calculatd. Hart-rat, hip-acclration, ackpack-acclration and stpfrquncy data wr synchronisd for ach voluntr y a slfprogrammd application. Nxt, ths wr procssd utilising th algorithms prsntd in prvious studis [27, 28 ] using Matla (Matla 5.3, MathWorks, Natick, Massachustts). First, synchronisd snsor data wr usd to idntify physically dmanding military-spcific activitis. Activity rcognition was prformd using a dcision tr dvlopd and validatd y Wyss and Mädr [ 27 ]. Th dcision tr assignd data at 1 min intrvals, ithr to 1 of 6 military-spcific activity classs or to an othr activitis class. Th military-spcific activity classs includd walking, marching with a ackpack, lifting and lowring loads, lifting and carrying loads, digging, and running. Scond, asd on activity rcognition and snsor data, PAEE was stimatd at 1-min intrvals. Thrfor, th activity class-spcific multipl linar rgrssions of Wyss and Mädr [ 28 ] wr usd, with hart rat and acclration as indpndnt varials. TEE valus wr calculatd as th sum of PAEE and rsting nrgy xpnditur (REE). REE was dtrmind using anthropomtric data applid to th formula for mals y Mifflin t al. [16 ]. To compar TEE with valus pulishd in th compndium of physical activity intnsity of Ainsworth t al. [1, 2 ], th rsults wr additionally xprssd as mtaolic quivalnt (MET) intnsity lvls. On MET is quivalnt to J/kg/min [ 2 ]. Using ths MET valus, th othr activitis class was furthr sudividd into 4 intnsity catgoris: inactivity ( < 1.5 MET), low intnsity ( MET), modrat intnsity ( MET) and vigorous intnsity ( > 6.0 MET). For som activitis, such as taking a showr or changing cloths during th day, participants took off thir snsors. Ths tim squncs wr addd to th low-intnsity activity class. Finally, stp-count data wr usd to stimat distanc covrd on foot in 2-s intrvals, according to th algorithm dvlopd in th first part of this study. On-way analyss of varianc (ANOVAs) with Tuky s post-hoc tsts for multipl comparisons wr conductd to compar anthropomtric data, PAEE, distanc covrd on foot and tim spnt in physically dmanding activity classs among wks and occupational spcialtis. Rsults Linar rgrssion twn SF and GV Body hight did not diffr twn study groups (179.4 ± 6.1 cm and ± 8.0 cm, p = 0.819) and had no significant influnc on GV in th rgrssion modl. Th rsulting linar rgrssion modl was: GV = SF Applying th linar rgrssion quation to data from th controldata group rsultd in a corrlation of r = 0.92 (p = 0) twn a stimatd GV masurd GV (m/s) stimatd GV masurd GV (m/s) c stimatd GV masurd GV (m/s) 3.00 man GV stimatd y linar rgrssions and masurd (m/s) man GV stimatd aftr Trrir & Schutz and masurd (m/s) 3.50 man GV stimatd y ranchd modl and masurd (m/s) Fig. 1 a c Bland-Altman plots on gait vlocity (GV) of th control-data group (n = 15) masurd and stimatd using a th linar rgrssion modl dvlopd in th prsnt study, th rgrssion from Trrir and Schutz (2003) and c th ranchd modl. Th dashd lins rprsnt th man of th diffrncs twn masurd and stimatd GV valus and th limits of agrmnt ( ± 2 standard dviations). Th full lin rprsnts th zro lin. dirctly masurd and stimatd GV. Howvr, th Bland-Altman plot showd systmatic undrstimation of GV for slow walking spds low 1 m/s ( Fig. 1a ). On th othr hand, GV stimation using Trrir and Schutz s rgrssion quation ( GV = SF ) was dmonstratd to mor accurat at a slow Wyss T t al. Amulatory Physical Activity in Int J Sports Md 2012; 33:

4 Training & Tsting 719 Tal 1 Anthropomtric data of participants in th 5 study groups. Rscu tchnicians (n = 45) Armourd infantry (n = 46) Fusilir infantry (n = 45) Rconnaissanc infantry (n = 44) Communications intllignc (n = 34) ag [y] ± ± ± ± ± 1.22 hight [cm] 18 ± ± ± ± ± 6.81 wight [kg] ± ± ± ± ± 8.32 BMI ± ± ± ± ± 2.20 BMI = ody mass indx Tal 2 Avrag daily physical activitis and dmands in Swiss Army training schools. Rscu tchnicians Armourd Infantry Fusilir infantry Rconnaissanc infantry Communications intllignc PAEE [MJ/d] ± ± ± ± ± 1.81 REE [MJ/d] 7.54 ± ± ± ± ± 0.47 TEE [MJ/d] ± ± ± ± ± 1.81 distanc on foot [km/d] ± ± ± ± 2.77.c.d 7.72 ± 1.52 marching [min/d] ± ± ± ± a,,c,d ± 6.99 running & sports [min/d] ± ± ± ± ± PDMH [min/d] ± c,d, ± ± ± ± inactivity [min/d] ± d, ± ± ± a,,c ± low OA [min/d] ± ± ± ± ± modrat OA [min/d] ± ± ± ± ± vigorous OA [min/d] 6.38 ± 1.89 a,c,d, ± ± ± ± 3.86 night s rst [h/night] 7.76 ± ± ± ± ± 1.78 PAEE = physical activity nrgy xpnditur, REE = rsting nrgy xpnditur, TEE = total nrgy xpnditur, PDMH = physically dmanding matrials-handling, OA = othr activitis a,, c, d and, rspctivly = significantly diffrnt (p < 0.05) from: rscu tchnicians (a), armourd infantry (), fusilir infantry (c), rconnaissanc infantry (d) or communications intllignc () walking spd, whras a growing undrstimation was osrvd with incrasing walking spd ( Fig. 1 ). Thrfor, th rgrssion of Trrir and Schutz [ 20 ] was usd for slow walking spds low 1 m/s (corrsponding to an SF of up to 1.42 stps pr scond), whil th linar rgrssion quation dvlopd in th prsnt study was usd for highr SFs. Avrag GV stimatd using this ranchd modl (1.97 ± 0.75 m/s) did not diffr from masurd GV ( ± 0.77 m/s, p = 0.281, CI-95 % = m/s); oth typs of data acquisition wr highly corrlatd (r = 0.94, p = 0) and showd no systmatic misclassification in th Bland-Altman plot ( Fig. 1c ). Amulatory physical activitis during Swiss Army BT 36 voluntrs (14.4 %) did not provid snsor data caus thy wr xcludd from th BT during th first wk of thir military srvic on mdical or psychological grounds. On avrag, th rmaining 214 voluntrs wr 20.6 ± 1.2 yars old, ± 6.6 cm tall, wighd 74.2 ± 10.4 kg and had a ody mass indx of 23.2 ± 2.8 ( Tal 1 ). Ag and anthropomtric data of voluntrs did not diffr among th 5 study groups. As voluntr involvmnt was low on Fridays, only data collctd on Mondays to Thursdays wr includd in th analysis. Of th snsor data collctd on thos days, 58.7 % wr usd for analysis. Th othr 41.3 % of data wr xcludd ithr caus participants did not war th snsors (61 % of data loss) or du to tchnical prolms or mchanical dfcts in th snsors (39 % of data loss). In th Swiss Army training schools invstigatd, th avrag PAEE was 10.5 ± 2.4 MJ/d, and trains covrd 12.9 ± 3.3 km/d on foot. Rcruits spnt 61.0 ± 23.3 min/d marching (30.4 ± 22.5 min/d with a ackpack), 33.1 ± 19.5 min/d prforming physically dmanding matrials-handling activitis, 36.2 ± 25.2 min/d in running and sports activitis, 8.1 ± 5.2 min/d in othr activitis of vigorous intnsity, ± 70.2 min/d in othr activitis of modrat intnsity and ± 30.0 min/d in othr activitis of low intnsity. During ± 46.7 min/d, trains wr inactiv ( Tal 2 ). Avrag stimatd PAEEs for th physically dmanding activity classs wr: 22.2 ± 3.3 kj/min for walking, 29.4 ± 7.4 kj/min for marching with a ackpack, 26.2 ± 4.0 kj/min for matrials-handling activitis and 34.1 ± 13.8 kj/min for running and sports. Thus, TEE intnsity lvls wr 5.3, 6.7, 6.1 and 7.6 MET, rspctivly. In most of th training schools invstigatd, physical dmands dcrasd from wk 2 to wk 8 of BT ( Fig. 2, 3 ). Avrag PAEE valus ovr all 5 study groups dcrasd significantly from wk 2 to wk 8, with a diffrnc of 2.9 ± 3.0 MJ/d. Discussion Enrgy xpnditur Th prsnt study assssd voluntrs daily PAEE sinc this valu rprsnts th intnsity and duration of physical activity. Rsults dmonstratd that rcruits in Swiss Army BT ar physically mor activ (PAEE = 10.5 ± 2.4 MJ/d) than th mal civilian population (4.6 ± 1.5 MJ/d) of similar ag, wight and hight [ 9 ]. Howvr, for a military stting, no othr PAEE data hav n pulishd so far. Thrfor, TEE was calculatd from PAEE and REE to compar th physical dmands in th Swiss Army with thos in othr armd forcs. TEE in th Swiss Army rscu tchnician, fusilir infantry and rconnaissanc infantry training schools (aout 18 MJ/d, Tal 2 ) was similar to valus assssd for various othr intrnational military BTs (17 18 MJ/d) of sim- Wyss T t al. Amulatory Physical Activity in Int J Sports Md 2012; 33:

5 720 Training & Tsting PAEE [MJ/d] Fig. 2 Physical activity nrgy xpnditur (PAEE) during daily military routin in wks 2, 4, 8 and 10 of asic training in 5 occupational spcialtis of th Swiss Army. Avrag PAEE valus ovr all 5 of th study groups significantly dcrasd from wk 2 to wk 8 (p < 0.05). 0 wk 2 p < 0.05 wk 4 wk 8 wk 10 rscu tchnicians armourd infantry fusilir infantry rconnaissanc infantry communication intllignc distanc on foot [km/d] Fig. 3 Daily distanc covrd on foot during military routin in wks 2, 4, 8 and 10 of asic training in 5 occupational spcialtis of th Swiss Army. 0 wk 2 wk 4 wk 8 wk 10 rscu tchnicians armourd infantry rconnaissanc infantry communication intllignc fusilir infantry ilar duration [10, 22, 25 ]. TEE in th Swiss armourd infantry training school (21 MJ/d) was in th uppr rang, whil TEE in communications intllignc (15 MJ/d) was in th lowr rang of ths comparativ rsults. During Swiss Army BT, th TEE valus ar in th sam rang as thos found in profssional athlts of similar ag and anthropomtry ngagd in thir daily routins including xrcis training [ 8, 24 ]. Profssional soccr playrs, for xampl, hav n found to xhiit an avrag TEE of 15 MJ/d [ 8 ], and lit cyclists during prsason training hav an avrag TEE of 19 MJ/d [ 24 ]. In contrast to profssional athlts, rcruits oftn do not hav a history of spcific physical prparation and adaptation to high physical dmands. Howvr, a rlvant diffrnc twn th daily physical activitis of athlts and rcruits is that athlts prform at high intnsity for a fw hours a day, whil rcruits prform mostly at modrat intnsity, ut for many hours a day ( Tal 2 ). Th avrag TEE intnsity lvls that wr stimatd during spcific activity classs in th prsnt study (walking: 5.3 MET; marching with ackpack: 6.7 MET; matrials handling: 6.1 MET; and running: 7.6 MET) corrspond wll to valus pulishd in Ainsworth t al. s compndium of physical activity intnsitis (for xampl, lvl walking at 4 mph: 5 MET; ackpacking: 7 MET; loading and unloading truck: 6.5 MET; running at 5 mph: 8 MET) [1, 2 ]. This indicats strong validity of th mthod for nrgy xpnditur stimation applid in this study [ 28 ]. Distanc covrd on foot Using th nw algorithm to stimat distanc covrd on foot, additional information on amulatory physical activitis can drivd from th ody-waral snsors applid originally for activity rcognition and nrgy xpnditur stimation according to Wyss and Mädr [27, 28 ]. Particularly in a military stting, distanc covrd on foot is a rlvant mtric for quantifying a soldir s jo rquirmnts. Rcruits in th Swiss armourd infantry training school covrd gratr distancs on foot (15.6 km/d) during daily military routins than trains in th US Army BT (11.7 km/d; rang km/d among th 10 companis invstigatd [ 14 ] ). Th distancs covrd on foot y Swiss Army rscu tchnicians, fusilir and rconnaissanc infantry rcruits ( km/d) wr in th uppr rang of comparativ data of trains in th US Army BT. Rcruits in th communications intllignc training school covrd shortr distancs (7.7 km/d) than trains in US Army BT [ 14 ]. Thr ar som possil xplanations for th wid rang of distancs covrd on foot in BT among diffring companis in th Swiss Army compard to th US Army. US Army BT provids gnralisd training to dvlop asic soldiring skills, whras in th Swiss Army BT, additional training is providd in ranch-spcific skills. Furthr, distancs to fild training aras diffr among Swiss Army arracks. Finally, it appars that school commandrs in th Swiss Army hav mor autonomy in dfining th contnt of thir training than US Army commandrs. Wyss T t al. Amulatory Physical Activity in Int J Sports Md 2012; 33:

6 Training & Tsting 721 Mal US citizns of similar ag (i.., 19 yars) prform an avrag of stps pr day [ 23 ]. Using an avrag stp lngth of 0.73 m assssd among young adults y Mnz t al. [ 15 ], a total daily distanc of 8.6 km/d is otaind. Thrfor, w conclud that trains in most occupational spcialtis of th armd forcs walk mor than comparativ civilians in thir daily routins. Dvlopmnt of physical dmands during BT It is a wll stalishd fact in sports and xrcis scincs that sujcts should gradually adapt to nw kinds of physical dmands. This is particularly tru for rcruits in th first wks of BT. Thrfor, th physical training programm should always start with an appropriat, rducd lvl of dmand and thn incras progrssivly during susqunt wks of training. Howvr, th prsnt study showd that th opposit is practisd, namly a high lvl of physical dmand at th ginning of BT (wk 2) followd y a dcras, rathr than progrssion, in physical dmand during th first 8 wks of BT ( Fig. 2, 3 ). Th sam pattrn of inappropriatly high lvls of physical dmand at th ginning and lack of gradual adaption in physical dmand for th first 9 wks of BT in British Army parachut rcruits [ 25 ] and South African Army rcruits [ 13 ] has n rlatd to an incrasd numr of injuris. This indicats that mthods must found to introduc a mor progrssiv dvlopmnt of physical dmand in Swiss Army training. Limitations Snsor dfcts and failur of participants to war all 3 snsors rducd th datast y 41.3 %. Th numr of complt datasts may hav n incrasd y any of th following: a smallr numr of snsors pr participant, daily survillanc of participant involvmnt or an improvmnt in th mchanical staility of th snsors. Th BT wks invstigatd (wks 2, 4, 8 and 10) rprsnt only a portion of th BT in Swiss Army training schools. It is possil that th wks not invstigatd containd diffrnt pattrns of physical dmands. Howvr, wks 2 and 4 rprsnt th GBT and wks 8 and 10 rprsnt FBT. Basd on th contnt of appraisals y school commandrs and thir wkly military training plans, th wks invstigatd appar to rprsntativ of all wks in ach part of BT. Strngths Th ojctiv mthod mployd was unotrusiv and did not rstrain daily military training. Body-fixd snsors wr usd succssfully to assss th typ, duration and intnsity of physical activity in diffrnt military occupational spcialtis. Thrfor, th mthod usd allowd ojctiv quantification of th physical jo rquirmnts of soldirs. An xampl of a dtaild charactrisation and comparison of diffrnt occupational spcialtis is prsntd in Tal 2. Implications This study provids novl rfrnc data for quantifying th physical dmands of daily military routins, and supplmnts alrady pulishd valus of nrgy xpnditur during daily military routins in th armd forcs of various countris. Furthr, th prsnt study is on of th first to quantify distanc covrd on foot. Morovr, to our knowldg, it is th first to ojctivly quantify th tim spnt in military-spcific activitis. This study dmonstrats that mor information on occupational physical activity can drivd from th rcntly applid odyworn snsors [3, 4, 14, 25 ] than only th quantification of dirct outcoms such as cardiovascular strain (using hart-rat monitors), physical activity intnsity (using acclromtrs) or stp count (using pdomtrs). For th Swiss Army, this study provids nw ojctiv information to dscri and compar physical jo rquirmnts across diffrnt occupational spcialtis. Conclusion Th masurmnt systm utilisd in th prsnt study yilds data comparal to prior studis that applid altrnativ mthods. Nvrthlss, th snsor-asd, ojctiv masurmnt systm provids mor information on daily physical activity and dmands than traditional, singl masurmnt instrumnts. Physical activity in Swiss Army training schools varis among occupational spcialtis. Howvr, th avrag daily TEE valus in all invstigatd occupational spcialtis ar within th rang of valus found among othr national armd forcs, as wll as among profssional athlts. 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