Heart rates during competitive orienteering

Transcription

1 BrJ Sp Med 1993; 27(1) Heart rates durng compettve orenteerng S. R. Brd PhD M Bol, R Baley BA and J Lews BA Department of Sport Scence, Chrst Church College, Canterbury, UK Ths study nvestgated the heart rate profles of 16 experenced, compettve orenteers (aged years) durng three compettve events. Each compettor was assessed over three dfferent types of course whch were classfed as: fast run (), slow run () and hghly physcal (). The results showed that all subjects recorded heart rates that were between 140 and 180 beats mn- for the majorty of each event (rrespectve of age or course type). The heart rate data ndcated that the actvty was largely aerobc but vared n ntensty, wth phases of strenuous anaerobc work. The type of course was shown sgnfcantly (analyss of varance; P < 01) to affect the mean heart rate attaned by each orenteer ( = 160, = 158, = 150 beats mn-), wth courses that requred more techncal skll and hence slower runnng producng lower mean heart rates; although the general physcal demands were smlar for all courses. The older orenteers (>45 years) recorded heart rate profles that were smlar to those of the young orenteers wth no correlaton beng found between age and mean heart rate whle exercsng. Keywords: Orenteerng, heart rates, cardovascular ftness, ageng Compettve orenteerng s a form of foot race whch requres both physcal ftness and navgatonal sklls. Usng a map (scale 1: or 1:15 000) and compass, the partcpants must vst a number of specfc control stes n a desgnated order; the wnner beng the person who completes the course n the quckest tme. The ages of the partcpants n orenteerng events range from under 10 to over 70 years and to cover ths range there are a maxmum of 15 compettve age categores (the exact number dependng upon the type of event) wth men and women also competng n separate classes. Events range n standard and are desgnated as beng: (1) local; (2) colour coded; (3) badge; (4) natonal. At any orenteerng event a number of courses of varyng length and techncal dffculty are avalable, and compettors partcpate n a course that s approprate for ther age, ftness and experence. To maxmze the techncal aspect of the sport, compettors on the same course start at ntervals of at least 1 mn. The venues for orenteerng events nclude local parks, woods, forests, heathland, open moorland Address for correspondence: Dr S. R. Brd, Department of Sport Scence, Canterbury, Chl.-t Church College, North Holmes Road, Canterbury, Kent CT1 1QU, UK ( 1993 Butterworth-Henemann Ltd /93/ and mountan areas. The terran over whch the event s run nfluences the dstance covered, the amount of clmb ncorporated nto the course and the 'runablty' of the ground (whch can vary from paths and grassland to heather, bracken, brashngs and dense undergrowth). The physcal nature of the sport means that t s a contnuous form of exercse that may last from less than 30 mn to over 2 h. Wthn ths tme the ntensty of the exercse wll vary accordng to: (1) the terran, whch may be uphll, downhll or flat; (2) the condtons underfoot, whch may be even or uneven wth obstructons such as undergrowth and brashngs; (3) the vegetaton, whch may be open or dense; (4) the techncal aspects of the course, whch may be easy, thereby permttng fast runnng, or dffcult requrng ntrcate navgaton and therefore a slower speed. Wth the ncreased popularty of orenteerng the ams of ths study were to nvestgate the heart rate responses of partcpants n a number of age categores, as ths would provde some ndcaton of the physcal demands of the sport. t would also provde an ndcaton of the heart rate capactes of relatvely actve ndvduals n a number of age groups. Materals and methods A group of 16 orenteers (sx female and ten male) from the Saxons Orenteerng Club of Kent volunteered to partcpate n the study (age range years). All had been orenteerng compettvely for at least 3 years wth 12 of the senors beng ranked natonally. The heart rate of each partcpant was montored throughout three 'Brtsh Orenteerng Federaton' compettve events, whch ranged n standard from colour coded to natonal (a total of 38 dfferent events) and ncorporated a varety of terrans. Before partcpatng n each event each orenteer declared themselves ft and free from any llness that could nfluence ther performance. n all events the partcpants ran at ther own self-selected competton ntensty n accordance wth the course's physcal and techncal demands. Heart rates were recorded every 15 s usng a PE3000 heart rate montor (Polar Electroncs, Kempele, Fnland) whch was also used to record the partcpant's splt tme at each control. Prevous research has found ths system to be relable, unobtrusve and not to nterfere wth the orenteers' runnng or concentraton'. The recordng of splt tmes requred no addtonal commtment by the partcpants as t s common practce among Br J Sp Med 1993; 27(1) 53

2 Heart rates durng orenteerng: S. R. Brd et al. orenteers who normally use a wrst stopwatch for ths purpose. The recordng of heart rate started as the compettors left the start box and stopped as they crossed the fnsh lne. After the event the data was loaded nto a BBC mcrocomputer (Acorn Computers, Cambrdge, UK) for analyss and each subject produced a detaled descrpton of ther run whch ncluded: (1) a copy of ther route marked on ther map; (2) a wrtten descrpton of ther strategy for each control and any dstnct ncdents that occurred. These could then be located accurately on the heart rate profle usng the recorded splt tmes and related to the recorded heart rates. A typcal heart rate profle for an event s shown n Fgure 1. Each subject was assessed over three contrastng areas n order to nvestgate the nfluence of terran and the techncal dffculty of a course on the compettors' heart rates. Whle all courses ncluded an element of fast runnng, physcally demandng terran and perods of lower ntensty exercse due to the need for complex navgaton, the courses could be classfed as follows: 1. Fast runnng low techncalty (). These courses requred a hgh proporton of tme to be spent on path runnng wth many of the controls beng sted n areas whch requred lttle complex navgaton. 2. Slow run and/or hgh techncalty (). These courses requred the compettors to spend a hgh a proporton of ther tme navgatng through relatvely dense vegetaton or across dffcult terran whch requred a hgh degree of complex navgaton. 3. Hghly physcal (). These courses requred the compettors to negotate a relatvely large amount of uphll runnng and often ncluded physcally demandng terran such as heather or waterlogged ground. The control stes for these courses were a mxture of hgh and low techncalty. The mean heart rates attaned for each type of course were then compared usng an analyss of varance for correlated data2. Results and dscusson The data for each subject are summarzed n Table 1 (events for each subject n chronologcal order). The proporton of tme (mean of three events) each subject spent wth heart rates of (1) less than 100 beats mn-; (2) beats mn'; (3) beats mn-; (4) beats mnk; (5) beats mnk and (6) > 180 beats mnk are llustrated graphcally n Fgure 2. The results showed that durng the orenteerng compettons all subjects had heart rates whch were between 140 and 180 beats mn' for the majorty of the tme. However, wthn each event the compettor's heart rate vared n accordance wth the ntensty of the exercse and terran. These results were supported by the comments made n the compettors' reports whch referred to phases of hard runnng and fatgue that could be located on ther heart rate profle. ndeed, strenuous phases of actvty, such as ascents or perods of fast runnng, often caused sgnfcant bref rses n heart rate that exceeded )A A B Fgure 1. A typcal heart rate profle for an event. Numbered vertcal lnes ndcate the arrval at each control ste (19 n total). 'A' ndcates the pont at whch tme was spent copyng down the frst half of the course at 'master ndcates maps' and 'B' the drop n heart rate assocated wth copyng down the second part of the course at 'second master maps' 54 Br J Sp Med 1993; 27(1)

3 Heart rates durng orenteerng: S. R. Brd et al. Table 1. and standard devaton of heart rates for each event and the percentage of tme each compettor spent n each heart rate zone. Male and female subjects are lsted as M and W respectvely Subject Age Type of event Duraton of event (s.d.) heart rate Percentage of tme spent n each of the heart rate zones (mn:secs) (beats mn-') (beats mn-') < >179 W 15 W2 30 W3 37 W4 37 W5 47 W6 62 Ml 14 M2 29 M3 32 M4 36 M5 37 M6 39 M7 42 M8 44 M9 49 M1o 55 87:34 35:26 78:03 101:16 101:19 120:21 92:43 60:33 79:56 53:20 62:27 81:04 60:47 90:30 55:39 54:57 70:36 75:43 90:09 60:02 153:06 99:05 96:21 93:45 100:59 138:12 54:18 95:49 76:35 74:39 71:47 102:36 120:46 115:41 109:27 89:30 88:25 84:52 62:30 57:47 78:23 90:03 65:06 95:46 169:43 172(2) 168(19.5) 163(2) 153(10.1) 150(8.4) 146(9.2) 163(9.0) 148(7.6) 168(10.2) 161 (9.2) 139(17.8) 156(16.1) 171 (8.7) 167(9.1) 153(1) 161(10.2) 155(15.2) 172(8.6) 176(9.6) 172(9.2) 179(11.7) 150(10.3) 143(8.8) 147(10.2) 170(11.7) 165(12.4) 157(14.3) 157(7.5) 162(8.3) 158() 157(8.7) 159(9.4) 154(13.1) 149(1) 141(15.2) 138(14.9) 161(8.0) 148(1) 152(12.8) 153(5.2) 157(4.8) 137(15.2) 125(16.3) 144(11.7) 138(1 7.6) 164(4.8) 156(9.9) 152(9.6) Br J Sp Med 1993; 27(1) 55

4 Heart rates durng orenteerng: S. R. Brd et al. Fgure 2. events) M1o p M9 M8 M7 M6 M5 t M4 To, M3 a) a M2 0 () Ml W6 W5 W4 W3 W2 W 0 m-11 M/M s s ued a-m-m.m.m.mmu-, mxff,..4t... mmmmmmm V111-1A N Tme spent n each zone (%)... O >179 o L o * < 100 Percentage of tme each partcpant spent wth heart rates (beats mn-') n each heart rate zone (mean of three mmmmmmmp....j ::: beats mn-. Therefore, the overall fndngs of ths study are smlar to others whch have reported the vared physcal ntensty of compettve orenteerng3-5, and as a consequence have advocated that when tranng for orenteerng the partcpant should nclude tranng methods such as fartlek and ntervals nto ther ftness programme as well as steady-state runnng. The effects of the terran and type of undergrowth were varable, wth elevatons n heart rate commonly beng assocated wth perods of fast runnng and uphll sectons. A comparson of the heart rates recorded durng events held on dfferent terrans revealed a statstcally sgnfcant dfference (P < 01) between course types. Those requrng slower runnng () and more techncal navgaton produced mean(s.d.) heart rates of 150(1) beats mnm that were slower than those obtaned durng events held on terrans that were 'hghly physcal' () (mean(s.d.) 158(9.6) beats mn-) or permtted a lot of fast runnng () (mean(s.d.) 160(1) beats mn-). However, even durng events that were classfed as 'slow run' all subjects mantaned heart rates that were above 140 beats mn- for most of the tme. t may therefore be concluded that whle the physcal and techncal nature of the courses dd nfluence the compettors' heart rates, all the courses placed suffcent physcal demands upon the partcpants to elevate ther heart rates above 140 beats mn- for a substantal perod. Detaled analyss of the heart rate profles, splt tmes and the compettors' wrtten descrpton of ther run revealed that the cause of the heart rate fallng below the tranng zone durng an event was usually the compettor pausng to copy down ther course on ther map mmedately after the start of a colour-coded event, and n some cases on the longer courses a smlar pause to copy down the second half of ther course at a second set of 'master maps' at the mdway pont (see Fgure 1). Ths dd not occur n badge and natonal events, snce the maps were premarked wth the co npettor's course. Another common reason for a fall n heart rate as the need to slow down n order to relocate when lost. n addton to ths, slght falls n heart rate were often observed when the compettors arrved at control stes (Fgure 1). These were assocated wth the partcpant pausng to work out the route to the next control, and subjectvely t was noted that these partcular declnes n heart rate were less frequent and less substantal n the heart rate profles of the more experenced orenteers who would attempt to plan ahead and sort out ther route to a number of controls n advance, thereby removng the necessty to pause at each control. Occasonally a slght rse n heart rate was observed when subjects made errors and ths could be assocated wth psychologcal stress, although n most stuatons an error resulted n a fall n heart rate as the subject slowed down to relocate hs/her poston. An analyss of varance test revealed a statstcally sgnfcant (P < 01) dfference n the mean heart rates attaned by the dfferent compettors. Ths could be due to a number of factors, ncludng: the dfferng levels of ftness of the ndvduals; dfferences n ther techncal skll; varatons n the courses run; dfferences n the level of physcal ntensty at whch the compettors run; and varatons n tactcal strateges. A regresson analyss of the compettors' ages and ther mean heart rate whle competng showed no sgnfcant trend n any of the three types of course, whch was somewhat unexpected snce f there s a general declne n maxmum heart rate wth age6 7 ths s also lkely to be reflected by a reducton n the submaxmal exercse heart rates; wth the older orenteers recordng lower mean exercse heart rates durng the events. However, ths was not the case 56 Br J Sp Med 1993; 27(1)

5 and an examnaton of the data (Table 1) shows that some of the older orenteers were exercsng wth hgher average heart rates than the younger orenteers. Whle ths could reflect a dfference n ftness t also ndcates that the older partcpants had relatvely hgh heart rate capactes and possessed the ablty to exercse wth relatvely hgh heart rates for prolonged perods. Furthermore, the results of ths nvestgaton clearly demonstrated that the older partcpants had heart rate capactes whch were n excess of those expected for ther age6 7. Whether ths was due to ther regular partcpaton n the sport, natural ablty, or a combnaton of the two t s not possble to say. However, regardless of the cause, the results of ths study ndcate that for relatvely ft ndvduals over the age of 45 years the commonly used formula for calculatng maxmum heart rates (220 - age)6'7 s napproprate and, as a consequence of ths, heart rate tranng zones whch are estmated from age-predcted values are lkely to be too low n ths group. Alternatvely, the fndngs of ths study could be nterpreted to suggest that orenteerng s excessvely strenuous for the older age groups; however, snce all the older partcpants n the study had been competng for at least 8 years and competed at ther own level of perceved exerton durng the study ths nterpretaton was not consdered lkely by the authors. These results therefore go some way to support the fndngs of other studes8'9 whch have suggested that the regular partcpaton n exercse can reduce the declne n maxmum heart rate that s assocated wth the ageng processl0-12 and can help to mantan a person's cardovascular capacty as they age. The overall fndngs suggest that orenteerng s an actvty whch places sgnfcant demands upon the partcpant's cardovascular system. t s therefore of suffcent ntensty and duraton to fulfl the crtera for good 'aerobc' exercse for relatvely ft ndvduals of a wde range of ages, as outlned by a number of authortes Heart rates durng orenteerng: S. R. Brd et al. Acknowledgements The authors would lke to thank all the members of the Saxons Orenteerng Club who partcpated n the study and Mr F. M. Hollday (Unversty of Loughborough) for hs advce on the statstcal analyss of the data. References 1 Squre P, Peck G. The physologcal demands of orenteerng: a prelmnary report, n The Proceedngs of the Brtsh Assocaton of Sport Scence Conference, London, UK, Cohen L, Hollday M. Statstcs for Socal Scentsts. London, UK: Harper and Row, Dresel U. Lactate acdoss wth dfferent stages n the course of a compettve orenteerng performance. Sc Orenteerng 1985; 1: Peck G. The physologcal demands of orenteerng. Sc J Orenteerng 1987; 3: Karkkanen OP, ed. Analyss of Orenteerng Competton (Fnnsh). Faculty of Physcal and Health Educaton, Unversty of Jyvaskyla, Jyvaskyla, 1986: 1. 6 Astrand PO, Rodahl K. Textbook of Work Physology, 2nd ed. New York, USA: McGraw-Hll, Lamb DR. Physology of Exercse: Responses and Adaptatons, 2nd ed. London, UK: MacMllan, Kavanagh T, Shephard R. Can regular sports partcpaton slow the agng process? Physcan and Sportsmedcne 1990; 18: Stenhaus LA, Dustman RE, Ruhlng RO et al. Cardorespratory ftness of young and older actve and sedentary men. Br J Sports Med 1988; 22: Andersen KL, Shephard RJ, Denoln H, Varnauskas E, Masron R Fundamentals of Exercse Testng. Geneva: World Health Organzaton, Londeree BR, Moeschberger ML. Effect of age and other factors on maxmal heart rate. Res Q Exerc Sport 1982; 53: Karvonen MJ, Kentala E, Mustala 0. The effects of tranng on heart rate. A longtudnal study. Ann Med Exp Bol Fenn 1957; 35: Amercan College of Sports Medcne. The recommended quantty and qualty of exercse for developng and mantanng ftness n healthy adults. Med Sc Sports 1978; 10: Amercan Heart Assocaton. Exercse and Your Heart. New York, USA: Amercan Heart Assocaton, The Coronary Preventon Group. Exercse-Heart-Health. London, UK: The Coronary Preventon Group, Makrdes L, Hegenhauser JF, Jones NL. Hgh ntensty endurance tranng n 20- to 30- and 60- to 70-year-old healthy men. Appl Physol 1990; 69: Br J Sp Med 1993; 27(1) 57