Race walking technique and Judging - the final report ofthe International Athletic Foundation research project

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1 [js^^ , 1990 I'^by l.f Race walking technique and Judging - the final report ofthe International thletic Foundation research project xel Knicker. Michaele Loch //; 19.S9 the Inlet national thletic Foundation commissioned a.scientific studv if race walking in order to provide informalion for athletes, coaches and officials. The auihors. working under the supervision tf Ptof. Peler rüggemann al the Institute of lhlelics of the German Sport University in Cologne, gathered dala in both compelilion and laboratory situations. Their objectives were lo imder.stand how competiiors achieved increased velocity; to confttm whelher or not this could be done whilst slayini> wiihin the rules as set oul bv the IF; and fo see if judges could accurately and consislenilv detect infringements of the rules. In their conclusion the authors recommend a change to the rule regarding the siraighlening <f the knee on each stride. Thc reaction if the IF Walking Committee lo this propo.sal has been included at the end ofthis article. * * r xel Knicker und Michaele Loch have holh participated in the lfunteriiatiimul.thletic Foundation Scientific Research Projects al the World Junior Championships In thletics in thens. 198; the World Championships in thletics. Rome. 1987: and the Games of the XXIVih Olympiad. Seoul Introduction In race walking, more so than in any oiher alhletic evenl. lechnique is strictly determined by compelilion rules. IF Rule 191 defines walking, as opposed lo running, and competiiors must adhere lo this definition or face disqualification. Rule 191 requires that thc leading foot make coniaci wilh the ground before Ihe rear fool leaves it. Failure to maintain con tact at all limes with the ground is known as "lifting". Rule 191 also requires the knee of the supporting leg to straighten in the vertical posiiion of each siride. Failure in this is known as "creeping". Throughoul their races competitors in race walking events are constantly observed by judges in order lo ensure compliance wilh the rules. The decisions made by Ihc judges can have a decisive intluence on ihe resull of any competition. Infringements of ihe rules may last for only a few milliseconds, yel may still be advantageous to the competitor. etection of rule infringements of such an extremely short duralion is certainly difficult for an untrained human eye: yel there is no provision in the rules for allowing race walking judges access to any technological assistance from Tilm or video cameras. 5

2 ims The aims ofthis investigation were lo: a) examine modern race walking lechnique to try lo detennine whether and how the demands of competition - i.e. increases in vehxity - can be met whilst remaining within the definition set oul in the rules; b) determine if judges can accurately and consistently identify infringements of the rules with the unaided eye; in other words, how do and how should judges ideniify infringements of llie rules? We divided our investigalion into two seciions. The first involved a kinematic analysis of lop level competitors throughout an actual race. We were particularly interested in measuring the effecis of faligue on the competitors as the race progressed. The second section examined those factors upon which judges focus their observation in arriving al their decisions, and whelher those decisions are influenced by external condilions.. Kinematic analysis of race walking under race conditions.1 Review of fhe literature There is liule scieniific liierature on race walking. Only a few authors have concentrated on walking technique and have done so mainly in comparison with normal speed walking. Murray, for instance, studied the performance of two Olympic race walkers in laboratory conditions, recording bolh kinematic and elcctromyographic paltcms. These tesls showed: 1. In comparison with someone walking at normal speed, race walkers of high calibre had higher stride frequency, longer strides, and shorter stance phases.. ouble limb support shortened to seconds. 3. Hardly any fiighi phases were identified. Occasional floats of less than seconds were registered. 4. Pelvic rotation in the transverse plane was greatly increased, up to values of 44" in race walking. 5. Rotation of the thorax doubled from an average 10" in speed walking to approximately t>' in race walking. However, the laboratory situation cannol take into accouni the effecis of competition on performance: these can have an emphatic influence on lechnique. Trowbridge conslnicted a mathematical moilel to measure the maximimi speed a race walker could achieve withoul lifting. He concluded that leg length was the key factor delermining maximum speed achievable by a race walker. Fronl this he deduced two ways of increasing walking speed. The first was to reduce siride length whilst simultaneously increasing frequency of stride. The second was to extend Ihe effective leg lenglh by increasing the mobility of Ihe hips. Trowbridge produced a formula whereby: ffective siride length = L^ x cos0 + a where L^ is the actual leg length of the athlete; 0 is the angle belween ihe mechanical longitudinal axis of ihe lotal leg and the ground and a is the amount of displacement of the fronl leg by hip extension. If. therefore, a walker can maintain his stride frequency whilst simultaneously increasing his hip extension, he will move taster. This means that walking velocity is a function of the rotational action around the hip axes.. Method We wanted to observe race walking technique under competitive condilions, using high-speed film. We were able lo do this at an international race walking meeting in Laval, France, on 1 June The programme included a 35 km event wilh a high calibre field of top walkers.

3 including international walkers from seven uropean countries. The eveni was particulariy suitable because the race consisted of fourteen laps of a.5 km course, so ihal the athleles passed our cameras 14 times. We hoped, therefore, lo be able to measure lhc effecl of their increasing fatigue on the key performance parameters by kinematic analysis. In fact, wc were only able lo analyse in depth a limited number of athletes, as follows: - One athlete for lap only - Three athletes for lap and lap only - One alhlete for laps and 13 Time analyses were completed for 9 alhletes. Two Locani high-speed cameras were used running al UK) fps. One camera stood at a right angle to lhc course, and the other filmed from an oblique fronl posiiion. calibration cage, size Im x m x m, was filmed before and afier the competition to establish whether the cameras had moved al all during filming, and also lo provide a scale for three-dimensional motion analysis using thc irect Linear Transformation technique (LT)..3 Re.sidis.3.1 Time analysis of flight limes and support times t this slage of the investigation our principal purpose was to establish whether athletes were capable of maintaining contacl with the ground, and. if nol. whether the night phases varied wiih the growing faligue ofthe athlete. With film running at HX) fps we were able lo measure time lo an accuracy of one hundredth of a second. The outstanding conclusion of the lime analysis was (hat none of the athletes could avoid lifiing in any phase of Ihe race. ach competitor was measured to show night limes in the firsl circuit as well as the lasl. Mean Highl times averaged 37 ms (milliseconds) and the range lay belween 0 ms (athletes C,, and ) and 70 ms {athlete ) - see Figure 1. We were astonished lo discover that the flight limes of individual athletes did nol vary from circuil lo circuil. The statistical dala shows that there is no correlation between flight times and the nuniber of circuits completed. uration of stance ',> ') and flight (^^m) phases - thletes - afhlefe e w lat-hlet- m^ lafhlefe & lathletc- C lathlet-e V 1 ^ 1» I cik-ouit: IO 1 13 Z 1 1 f» {-ime J[s] Figure 1 - i>urulion of stance and (lighl phases: athletes - 7

4 z total s.l. single s. I. ('igure : efinition of single and tolal stride lenglh TTie same holds true for ihe stance phases. No significant changes in the duralion of Ihese were evident throughout the race. Support limes ranged from 90 ms to 30 ms with a mean of 70 ms. See Figure 1, This analysis shows that athletes maintain their own individual walking rhylhm which scarcely varies throughout the race..3. Stride Lengths We measured stride lengths in two fonns: a. Total stride length is from touchdown (heel) to nexl touchdown of the same fool. b. Single stride length is from take-off (toe) to touchdown (heel) of opposite feet. Total stride length, iherefore, is greater than the sum of two single stride lengths, including the measuremenis of both of the feet plus any flying distance involved. These definitions are illustrated in Figure. The overall mean of total stride lengths was.5ni wiih a range of.09 lo.4m. The mean of single stride lengths was 0.8Hm wiih a range of O.Si lo LOOm - see Table I. The data shown in Table 1 reveals a significant decrease in siride lengths as the race progresses. Comparing all the lotal siride lengths measured at lap w ith those fiir lap. there is a mean reduction of 0.09m. In the same laps the mean reduction in single stride lengths was 5m - exactly half the figure for lolal stride lenglh. This is because, as we saw above, athletes did nol show varialions in Highl times as the race progressed: therefore no variation in flight distance entered into the equation. It is significant thai the only athlete we were able to measure beyond the half-way poinl in the race, athlele, showed a reduction in total stride length at each further point where he was measured.,3.3 Centres of Graviiy a) Heighl varialions nalysis ofthe height of athletes' centres of gravity reveals lillie variation. The vertical oscillation is low, as was expecled. It ranges from 0.0 to 0.07m with a mean of only m. Table 1 - Single a nd total stride lengths (sfl) for athletes - (in meires) Name C ('Jrcuil 10 1.^ Total si,.15.5,.1,3.5.4.m Single sl/l , Single sl/ 0, , S

5 The absolute heights measured for centres of graviiy are almost identical at the moment of lake-off and ihe momenl of touchdown. There is no correlation to be found between the dislance walked and the heights of centres of graviiy. These remain constant for all athletes belween laps and - see Table. However, athlete, who was still walking in laps 10 and 13, showed higher movements of the centre of gravity in these laps than in laps and. His minimum heights were close to those of the earlier laps hut the maximum heights were markedly increased - especially in lap 13 nearing the finish - and more than double ihe distance over which all the others were measured. We only have a sample of one from which lo decide how significant this is. b) Velocities Table 3 (on the following page), shows that the maximum velochies (vmax) of athletes' centres of gravity during a total Table - Height of centre of gravity of athletes - (in metres) Name Circuit C to 13 Minimum o.n 0.^ Q.90 ÖM 0J : ;:9t : ;85 0^ O^S 085 0:8S om 0.9Q Maximum 0, ,93 0J9 0; : ^3 0:93 ifterence {).{)? ,03 0, ,04 0, O T Heighl 0, Ü.9I TO Height ,95 0, , ,93 0,

6 stride cycle ranged from 4.5 metres per second (m/s) to 3.79 m/s. ifferences belween velocities at takeoff (vto) and touchdown (vt) were erratic. There is no clear pattern indicating touchdown velocities being consistently faster or slower than lake-off velocities. There is however a slight decrease in velocity as ihe race progresses, although Figure 3 shows an analysis of alhlete where maximum velocity was sometimes higher in lap than in lap. See Figure 3. The speed a race walker can achieve is detemiined by stride length and stride frequency. We showed in paragraph.3. (above) that stride lengths shortened as the race progressed. thletes would iherefore need to increa.se their siride frequency in order lo mainiain velocity, bul camera analysis shows ihat they did nol. Table 3 Velocity of centre of gravity of athletes - (in metres per.second) Name Circuit vmax \min vtu \YO 30 C 10' 13 4, , , S , ' : : , , in

7 velocity of CG 5.0 Im/s] 4.0 X 3.0? -^y^^^ "^^/P^-.0 time Is] Figure 3: Velociiy of cenire of graviiy - thlete This means thai there was a reduction in the drive or ihrust produced by the alhlete. causing a loss of vclocily as the race progressed. This can be attribuled lo the increasing onset of fatigue..3.4 Rolalion and hip mobility Looking forthe reasons why stride length shortened as a resull of growing faligue. we returned to the idea of Trowbridge. He suggested that walking speed could be increased by extending effective leg lenglh through increasing hip mobility. The motion of the hips is a rotational action represented by the degree of distortion belween the hip axis and the shoulder axis. We therefore expected to find decreasing distortion correlating with the decreasing stride lengths observed as the race progressed. We did, in facl. find clear reductions of distortion corresponding w ith distance covered. Figure 4 and Table 4 show marked lateralizaiions of hip motion. thlele. for inslance. rotated in a range from 5'^' to 31" to the right and 48" to 51" to the left in lap ; whereas the figures for lap were 19" to ts- istortion M %^>^-**yj - -*^ N-W Circuit V^ ' timelsi'-, ^ Figure 4: iitturliun uf the hip iiud shoulder a\i^ 31

8 Table 4 - Maximum values of distortion between hip and shoulder axes Name "Max (lap ).Mean Max (lap ).Mean ifference 38" 4" " " 4-49" 4-39» » 19-9» " * 30" " for the right and 7" to 9" for the left side..3.5 Knee ngles The melhod used for our kinematic analysis defined angles in a range of 175" to 185" as representing an extended knee. Table 5(a) (righl leg) and 5(b) (lefi leg) show that maximum knee angles almosl invariably fall within the " parameter of full extension. These tables also show that at the moment of touchdown athletes' knees are close to. or at, full extension - as demonsiraied on the first photographic frame showing the fool on the ground. Considerably lower values are seen at Ihe moment of lake-off (first frame showing the fool off the ground); these are due to' the eariy preparation for the forward swing following ihe support phase. Figure 5 shows a typical pattern of knee angles for a lotal siride cycle, ll does nol indicate any tendency lo bent knees during the support phase. The deviafions from the extension line all fall w ithin our staled parameters for full extension. These results are consistent with our findings on height variations in the centres of graviiy. enl knees during Ihe support phase would lower the centres of graviiy and increase thc ranae of oscillation. ^T Figure 5 - Progression of knee angles during one stride cycle

9 Table 5(a) Name H c Table 5(b) Name C n K I-: KCN; - Knee Lap Knee Circuit angles angles T(l = T;ik of right leg Max I77" 187'' ' 177'- 17.5" 1 7.5" t74" 178' 177" 175" 177" of left leg - Max 175" 178^^ 177* 17?" 179' 174" 17-17T' 17" 174" 179" 17" 180' 178' 177" 173' - thletes - Mill 9 100" IO(f 95 97' " 103" 98" 94" 10' 97" ' " IO!" thletes.min 87' 100" 91" loir 101" lol' 10" 9«" 101" lll.v 95" 107" I OL IOS'- -olt T - Tnuclniowii TO 153" 1.S" I.S" 14" 1.54" 1" 13" 158" 155" 15^>' 151" 15{>' 153" TO 14" 1411' 14" 14.^" I5l>' I4.V 148' 14" 144" 158" 154" 14.3" 157" 15" 15.5" 143" Tl) 17" 175" 175" I " 174" 17^ 173^ 171" 17" 17«' " 177" T 177" 17" 177" 175" 170" 174" 17.1" 171" I77" 177" " 174 ISt> I7t>' 171"

10 enl knees would also affect the athlete's angle tif forward propulsion during the support phase, aiming it upwards and certainly increasing lhc risk of lifting. ddilionalk. bending Ihe knees tluring the support phase would cause negative physiological effecis. The load, which is fully borne by thc knee joint if extended, would he transferred lo the thigh muscles, especially ilic quailriccps. This would cause addilional fatigue and have a negative infiuence on endurance.,4 Coniittsitni Kinematic analysis of ihe 35 km evenl showed that none of the athletes could avoid lifiing. and that the extent of lifiing could not be related to ihe dislance covered. The parameter most conspicuously influenced by distance covered, and therefore by increasing fatigue, was siride lenglh; this decreased during lhc race as a resull of reduced range of hip motion, as measured by the angles of disioriion between the shoulder and the hip axes. In conlrasl. our analysis shows that none of ihe alhletes monilored showed any infringements ofthe rule concerning knee extension in the suppori phase. Theoretical consiiicraiion indicales thai no advanlages are conferred upon lhc aihleie b\ bending of ihe knee. 3. valuation of judging 3.1 im In the introduclion to this report we referred to the extensive influence which the judges* decisions can have on the result of any competiiion. Judges interpret the rules and make their decisions unaitled by any fomi of technical suiiport. Thc limiting factor, therefore, is the abilit\ of the human eye lo cope with lime, space and movement. Subjecli\'e impressions also enter into judgements and this is a principal reason why disqualificatitin cannol be on the decision of one judge alone. 34 C)ur aim in this section ofthe investigation was to examine the reliability of the decisions of the judges by determining whether or not they were able consistently and accurately lo ideniify infringements of the rules. 3..Method Three judges - two Gennan national judges and luie member of the Panel of Iniernaiional Walking Judges - and iwo national level athleles took part in ihe lest. The judges were asked to classify thc walkers' lechnique based on an observance of the official rules. n evaluation formula was prepared which broke down thc questions of lifiing and knee extension inlo three categories each, as follows: 1. No lifiing observed. Flight limes acceptable 3. Flighi limes will lead to disqualification 4. Knees fully extended 5. Knee bending acceptable. Knee bending will lead to disqualification. ach athlete walked looom indoors, passing an observation area 3()m long 10 times. They then went OLiiside and walked 30()(Jni in thc field al free speed. This was repeated 5 times wilh the field walk omitted on ihe fifih repelilion. ach w alker covered a uual dislance of I T.OOOm and passed ihe observation area 50 limes. Thus each judge made 100 evaluaiions of flighi phases and knee angles. The actions of ihe walkers were simullaneously filmed with a standard video camera (Sony XC 35 p) and a highspeed video camera (NC HSV 400) running al a frame rale of (K) fps. The high-speed video was analysed for fiight limes and knee angles for maximum statistical accuracy. The standard video was presenied for further evaluation by the judges in the aficrnoon. ihc walking having laken place in Ihe morning. The sequences of film shown to Ihem were chosen at random and

11 consisted of 0 pa.ssesof the walkers through the observation area. The purpose of Ihis was lo ascertain whether the judgement of walking technique could be improved hy the use of lechnical support such as standard video. 3.3 Ke.stdis a) Flighi times - high-speed video analysis The results confinned the findings of the first part of this investigation. Neither ofthe athleles had been able to avoid Might phases in any of the 100 passes. Flight limes registered between 0 ms and 70 ms and were evenly distributed. The mean fiighi time was 40 ms. The corresponding value in the video was slightly higher al 4 ms and the distribution was comparable. s a control nine passes were re-run twice. b) Knee angles - high-speed video analysis s in the Laval race, this test revealed no knee angles of less than ISO" (+/- 5'~'f I. lhletes* knees were always fully exiended when in the vertical position ofthe support phase. This corresponded wilh the athletes" own subjective evaluation that they would be unable to walk with deliberately bent knees. Thus ihcjudgesconiinually selected item 4 on Ihe evalualion lormula. i.e. knees are fully extended Judges identificalitm of flight pha.ses a) Live silualion The judges idenlilied 41 flight phases. None of the judges made a decision to disqualify based on Ihe fiighi phases he identified. The mean fiighi lime of the idenlifieil phases was 4 ms. fhe mean of the fiight limes which were nol identified was 39 ms. This indicates a ditliculty in recognizing fiighi limes shorter ihan 50 ms. Wc Iherefore separated the llighi phases into Iwo gioups. The firsl was of limes less than 50 ms (T<50 ms) and the second of times of 50 ms or more (T>50 ms). In the total sample there were 5 cases of times less than 50 ms and?i5 cases of more ihan 50 ms. Table shows the judgements of the Ihree judges broken down b\ the two groups of flight phases. There are very substantial individual differences beiween the three judges. It is remarkable thai, although the judges agreed on 4 (Kcasions ihal there was no lifiing. there was not one single occasion on which ihey agreed that an athlele was lifiing. b) Video Tesling judges* evaluations of w alking technique - especially Ihe question of lifiing - using video as an aid was done on the assumption that the video screen would bring the key points to be observed (the Table - isi ribution of identified flight phases live situation Judge Total T<5I) ms T>=50 ms f t Together 41 t 0 CoiTcspontlence [{LlKllCClUiniLLlI Researcli loi)

12 moments of touchdown and take-ofo closer together than in the live situation. Thus the simultaneous observation of both feel, and identification of fiighi phases, ought to be easier when miniaiuri/ed onto a video screen. 0 passes from the morning session were re-run for evaluation on video in the afternoon. s a control 9 of them were presented twice. 41 of the 0 passes (8.3%) had flight phases of less than 50 ms. The other 19 (31.7%) were equal or longer than 50 ms. The three judges identified a total of 37 (1.7%) fiight phases. This was an improvement of 18% compared lo the live situation. On three occasions, all judges agreed on examples of lifting, and on 37 occasions ihey agreed that no lifting took place. Table shows a summary of the occasions on which the three judges identified flighi phases. Most inleresting was the comparison belween the direci (not video-supported) and the indirect (video-supported) judgements. Judge showed a variation of 17 occasions (8.39}) between the video-supported and live occasions. Judge showed 15 (5%) and judge C 9 (15^/.). Looking al the control group of 9 passes that were each re-run twice in the afternoon video test. Ihere was a surprisingly high consistency from the judges. Judge made different decisions for the ideniical pass only once: judge three times; and judge C twice. 3.5 Judges' evalualion of knee angles We have already shown that kinematic analysis produced no cases of benl knees in any phase of our tesling. Nevertheless, the judges identified benl knees in 48'^ of all cases. lso there was a ver>' high rate of 31% where judges agreed on individual cases thai bent knees had tkcurred. ll is also noticeable thai differences 3 between the individual evaluations are much less than we saw with the flight times. These differences are seen to be even smaller in the ease of the video- assisted judgements. See Table C. With video assistance ihe judges still identified benl knees in 49% of all cases. The level of agreement of all three judges on individual cases was 40%. If we compare the varialions belween the direci (live situation) and the indirect (video-assisted) judgements, there is a switch of SO*!^). This means that every second judgcmcnl of benl knees in the video assessment had been defined as straight knees in the live situation earlier in lhc day. From this we can only conclude that the judgement of knee angles is inconsistent and inexact. 4. Conclusion It can be concluded from the study that. on the issue of lifiing. judgements were improved where ihey were supported by slandard video filming as far as the overall idenlificalion of lifiing is concemed. However, wiih all three judges "agreeing" (i.e. making ihe same judgement for the same case) on onlv 5% of actual cases, the reliabilily of judges* decisions must still be called into question, It is possible that a larger sample of judges may have provided more valid results, but this was not available lo us. On the question of knee angles, all ihe results of this sludy. together with the kinematic analysis, lead us to suggest that a change lo the rule should be considered. The primary argument for this is that we did nol ideniify any case in which a walker's knee was nol exiended in its vertical uprighl posiiion. The secondary argument is Ihat we cannot conceive of any advantage lo the athlete in failing to walk with an exiended knee. Furthermore, in any evenl it is evident Ihal il is extremely difficult for judges to identify infringements of the current rule.

13 Table l{ - istribution of identified flight phases - \ideo situation.fudge Iitlul i<50 ms T>^50 m.s C a Togclhcr Correspondence 3 1 iomechaniciil Research Key: T = lime ms = milljsccnrals Table C - Oisl ribution )f identified knee angles Live SiiuaiiiHi,ludKe xtended Knet^ ent Knees C Together CorrespninJence 31 iomechanical Research KHI 0 Video.Siltiaiiun Judui' Fxtended Knees ent Knees C Tcigclhcr m Co rrc spitn dc nee 4 Uiinnechanicat Re,>e birch

14 RFRNCS Llt^RSFL. K.H.: SCHRÖTR G.: Grttmllaaeii llcr UHlitathktiL erlin. 197^. FRliKTOW..i SUSt.nW. F.: intciliinft tier.s/>i':i/(\i lifii Tniiiüin'sl>iiii)'rii fur uns.spnritit In- (iciicn. LeiciiUUhielik 0 in Leichtathletik URVCH, R-: SCHRÖTR. G.: Zur Tfchnik urnl Ltiinyri^c Jv.\.spitrtlulii'ii Gehen.<i im (' nuiilunii-iitruiiun-4. Lehre der Leichtathletik 34 in Uiehiaihletik MURRY. M.P.: GUTN. G.N.i MOLLfNGR, L..: GRNR, G.M.: Kiiwniatic and lcitraniyofirapliif Puttcnis of Olympic Race Walkers. The.\mcrican Journal of Sporis Medicine. 19S3, 11. NIKOLII. F.: FRUKTOW..: ie yiuwiisciil'ii Merhmilc ilcs Gclwiis. Leichtalhtelik 4, 197.\ TROWRIG.,.: WalkinR or Running - When does Liftinfi Occur.'.athletics Coach I. 15. Kxtract from the Minutes of the IF Walking Committee meeting. Split, Yugloslavia, 8/9 ugust 199Ü 3S "The Committee concluded that the report was most valuable and included many interesting points. The Committee noted in particular Professor ruggemann's own conclusion that "...a bigger sample of judges might have conferred a greaier validity upon the investigalion but was not available...". The Coinmiliee agreed that the sample was loo narrow. and, based upon ihe material in the report, recoinniended that no change should be made to Rule 191."