33 Activity profile, heart rate andblood lactate of futsal refereesduring competitive games

António Rebelo,’ António Ascenção,’ JoséMagalhães’ and Peter Krustrup2‘Universidade do Porto, Spain; Department of Human Physiology, Universiryoí Copenhagen, Denmark

Jntroduction

Several recent studies have evaluated the locomotor activities and physiologicaldemands of football referees and assistant referees (Bragada, 2001; Krustrupand Bangsbo, 2001; Krustrup ei ai., 2002; Helsen and Buitynck, 2004; Castagnaec ai., 2005; Reilly and Gregson, 2006). Such studies have provided importaminformation about match speciflc physical testing and training oí football matchofficials. Futsal, the FIFA-regulated indoor football, has become a popular indooraltemative to football, with miii ions of players and fans worldwide. However, thescientiftc knowledge regarding the physicai demands of fuisal playing is ratherLimired and so far, no studies have investigated rhe accivity profile and physiologicaldemands of íutsal reíereeing. Despite some similarities with football refereeing,several ftitsal-specific features, including pitch size, number aí players, game rulesand position of thc referees may impose distinct activity proifies and physiologicaldemands. Thus, the aims oí the presem study were to describe dite activky profileof futsai referees during cornpetftive games, including number aí activity changes,total distance covered (TD), high-intensity running (RIR), sprinting (SPR) andsideways running (SR) and to examine the physiological demands by measuringhearr rate and biood lactate. In addition, intermittent exercise perfonnance offutsal referes was determined by the Yo-Yo lntermittent Endurance Test, levei 2(Yo-YoIE2).

Methods

Panicipants

Twelve high-level Portuguese futsal referees (33.0 ±5.Oyears; 1.73 ±0.05m; 73.2±8.4kgand 15.7 ±5.4% fat mass) participated in thisstudy. TheYo-Yo intermittentendurance levei 2 test performance was 975 ±237 (rangc 760—1240m). AlI theparticipants had at least more than five years of experience in the top Portuguesefiutsai teague.

192 Rebelo, Ascenção, Mogoihaes and Kruserup

Acdviey profile analysis

Six referees were fitmed during matches of the 2005—2006 Portuguese top leagueseason to determine their locomotor activity. For this purpose, rwo VHS movie

(NV-M50, Panasonie, Germany) placed ar the side of Lhe pitch (leveIwith the half-way tine, at a height o( abour 15 m and at an approximate distanceof 15 m of the touch tine) were used. Each camera obtained dose up images fromeach referce. The videotapes were later replayed for computerized time—motionanalyses (Krustrup and Bangsbo, 2001). The locomotor panem cacegoriesincluded standing (Okm.h’), walking (ókm.h-1), jogging (8km.lr’), tow-speedrunning (I2km.h-’), moderate-speeci running (l5km.h-’), high-speed running(lBkm.h ‘),sprintíng (2Skm.h’),sideways (lOkm.h-1) and backwards (lOkm.h ‘)running. The march activities were tater divided into total distance covered, high.intensity running (HIR> 15 km.lr’), sprinting (SPR) and sideways running (SR).

Heari rale and blood lactate

Heart rate (HR) was recorded ar 5 s intervais throughout each game using a PolarVantage NV heart raLe monitor (Polar, Kempele, Fintand). Btood samptes werecoltected fi-om the ear tobe ar rest and 1—2 mm after the end of the game, andwere irnmediately analysed to determine blood lactate concentration using a YSI1500 S (Yetlow Spring lnstruments, Yellow Springs, OH, USA).

Staristks

The data are presented as means and standard devíarions. Difference in heartrate during the firsr and second half was tested for signfficance using a pairedt-test. Changes in match activities and heart raLe withmn each lømmn period ofthegame were evatuated by one-way anatysis of variance (ÁNOVÁ) with repeatedmeasures. The leveI of significance was se at 5 per cem.

Resutts

Accivity projile

As can be depicted from Table 33.1, tire number of activity changes was as high as1771 ±314 (±SD) over —Somin, which corresponds to a change in activity each2.7s. Total distance covered was 5.61 ±0.82km of which high-intensity running,sprinting and sideways running accounted for 0.93 ±0.18, 0.18 ±0.07 and 1.00±0.46km, respectivety. The number oíHIR and SPR bouts was 137 ±21 and 19±8, with a mean duration o(—1.3s,

ToMe 33.! Activity profile o( futsal rekrees cluring competitiva gamas, data are means ±SD (ri = 6)Standbag Walking Jo~ing Lciw spced Moderare High S$ni S&leways Backwards Total

specd speedPercentage of total time Mean 49.3 29.7 4.9 3.7 2.2 1.3 0.5 7.4 1.1 100.0

SO 6.9 2.1 1.1 1.0 0.4. 0.4 0.2 3.5 1.0 0.0l4umberoírcpecitions Mean 396 549 182 116 69 49 19 166 27 1572

SD 12 32 43 23 10 13 8 73 23 153Distancecovered(m) Mean O 2411 532 594 438 311 181 1000 143 5610

SD O 259 113 146 60 89 77 459 131 474Duration (s) Mean 6.1 2.6 1.3 1.5 1.5 1.3 13 2.4 1.7

SD 0.9 0.2 0.0 0.1 0.1 0.0 0.1 0.5 0.5

1

194 Rebelo, Ascenção, Magalhães and Krustrup200

j’iao0.éleG

1140

~120

100

1-1earc iate

An example ei a ftitsal referees’ heart rate response is given in Figure 33.1. Meanheart rate during a match was 146 ±1 beats.min ‘corresponding to 78 ±6% aímaxiznal heart rate (HRmax 191 ±9beats.min-’).

The mean heart rate was Iower (P-cO.05) in rhe second halí compared tethe ftrst half (143 ±13 vs l49±141,eats.min’). The mean heart rare was lower(P’c0.05) in the uirst, third and (ourrh lO—min period of the second halfcomparedto the first lO-min period ofthe first half (Figure 33.1). Peak heart rate during a

80

First halt Second MI

40 50 80 10 80 90 100

Time (mm)

Mni~los b.p.n,.

142

-20 -lo O lO 20 30

Figiue 33.1 An example ei the heart rate response ei a fursal reíeree during a competitivegame, with mean heart rates during the first and second hali aí 150 and 142 beacs.min-’respectively; the heart rate profile clearly reflects the incermittent feature o( the íutsalgame

190

?b60

duo.0

160a,

usa

140

130

120

110o

Time (mm)

Fig.tre 33.2 Mean heart rate (fihled bars) and peak heart rate (open bars) for referees in10-min intervals during competitive íutsal games; data are means ±SD (n = 12); # denotessigniíicant difference from 0—10 mm

0-10 10-20 20.30 30-40 40-60 5040 80-70 70-80

Activiry piofik, hean rae and blood lacrare offursalreferees 195

match was 176 ± l4beats.miiv’ or 92 ± 7% of maximai heart rate. Heart rate wasobserved to be in the range of 70—80%, 80—90% and 90—100% of HRmax for 37±4,41 ±6 and 9 ±3 of total time, respectively.

Biood laccace

Biood lactate was 1.5 ±0.5 (0.9—2.8) mmoi.1’ after the game. This value washigher (P<0.05) than ar rest (1.0 ±0.3 (0.8—1.5) mmol.1’).

Discussion and conclusion

Futsal is becoming a popular indoor alternative to soccer, with specific rules andmilhons of players and fans worldwide. Given the growing competitive levei of thegame observed in the Iasc decade, increasing physiologicai dernands have beenimposed upon fursai referees. However, in contrasr co soccer, and to the best ofour knowledge, this is the first study that anaiysed the activity profile of ftitsalreferees during competitive matches as weIi as the physioiogicai demands imposedby the game. Time—motion analysis showed thar Futsai referees covered a Iowatotal discance (5.6km) than both top levei soccer referees (10.3 km) and assistamreferees (7.3km) (Krustrup and Bangsbo, 2001; Krustrup ei ai., 2002). However,the futsal referees perbrmed a higher number of sprints and sideways runningboucs than foorbail referees, with values corresponding co chose of assistamreferees. Like footbail match officiacing, fursai refereeing is highiy intermittent,with a cremendousiy high number of accivicy changes. Acrually, che high-intensiryrunning bouts are even shorter chan for referees and assistam referes with averagesprint distantes of Iess chan LOm. The hearc rate data recorded in che presentstudy show char the aerobic ioading is moderate-to-high for futsai referees duringa game. Thus, average heart rates were —145 beats.min’ which is higher thanfor assistam referees bur iower than for referees. Unexpeetedly, the blood lactatevalues were only siighciy higher than resting values afta cite game (1.5 vs 1.0 mlvi).This does not mean that blood lactate values are not high for some fursai referesafter che most intense periods of a game, but it cleariy scresses thac the iactacidanaerobic energy tumover is of Iess importance for futsai referees than foorbalireferees and assistam referees having average values of around 5 mM after games(Krustrup and Bangsbo, 2001; Kniscrup a ai., 2002). These f’indings may weii bereiated co the duration of the high-intensicy actions, which are shorter for futsalreferees (1.3 s) than for footbaii match officiais (—2 s).

In conciusion, futsal refereeing is generaliy characterized as intennittent exercisewith numerous very briefbouts of fast speed and sideways running incerspersed byiong iow inrensiry recovery periods. Heart rate was moderate-to-high. lnterestingly,blood lactate was low suggescing that a majority of the anaerobic energy turnoverwas provided by breakdown of adenosine triphosphate and creatine phosphace.These data reinforce the importance of sprint performance and che abiiicy corecover between intense exercise periods for fursai referees. Therefore, che abilityto perform repeaced brief sprints and to per(orm intermittent match-specific

196 Rebelo, Ascenção, Magalhões and Kruscn4,

movements including sideways running, should be incorporated in training andtesting strategies for fucsal referees.

References

Bragada. J., 2001, Avaliação da intensidade dos exercícios de treino. Treino Desponk.o,14(3):18—26.

Castagna, C., Abt, O. and D’Onavio, 5., 2005, Competitive.Ievel differences in Yo-Yointermittent recovery and twelve minute run test performance in soccer referees.Joun,4Screngda Condiüoning Reseo.rch, 19(4): 805—9.

Helsen, W and Bulrynck, J.B., 2004, Physical and perceptual-cognitive demands of topclass refereeing in association footbaIl. journol af Spons Sciences, 22: 17949.

Krustrup, R and Bangsbo, J., 2001, Physiological demands of top-class soccer refereeing inrelation to physical capacity: effect of intense intermittent exercise training. Jounwl o)’Spons Sciences. 19: 881—91.

Krustrup, P, Mohr M. and Bangsbo, J., 2002, Activity profile and physiological demandsol topclass soccer assistam refereeing in reladon to training status. Journal o)’ SponsScienca, 20: 861—71.

ReiIly, 1 and Oregson, W., 2006, Spectal populations: the refere and assistam referee.Journol o)’ Spons Sciences, 24: 795—801.