THE IMPORTANCE OF ARM-SWING DURING FORWARD DIVE AND REVERSE DIVE ON SPRINGBOARD

Transcription

1 THE MPORTANCE OF ARM-SWNG DURNG FORWARD DVE AND REVERSE DVE ON SPRNGBOARD Ken Yokoyama Laboratory of Bomechancs Faculty ofeducaton Kanazawa Unversty Kanazawa, Japan J unjro Nagano Department of Physcal Educaton Tenr Unversty Tenr, Japan Moto Fukushma and Hroh Yamamoto Laboratory of Bomechancs Faculty ofeducaton Kanazawa Unversty Kanazawa, Japan ntroducton n the perfonnance of sprngboard dves from ether the forward or reverse group, the compettor begns wth an approach consstng of a mnmum of 3 steps followed by a hurdle and take-off. To date, lttle, f any nformaton of the approach, hurdle step, and take-off has been publshed n Japan (Mller, 1974, 1981, 1984). Ths study focuses on the performance of a top Japanese woman dver. Analyss offlms provded a unque opportunty to study sprngboard dvng perfonnances and to develop a data base on selected contnuous temporal fonn and angles of the hurdle step and take-off of an elte female sprngboard dver. The 125

2 purpose of ths study s to dentfy the segmental sgnfcance of armswng durng dvng performance, especally wth regard to both the forward dve and reverse dve on the sprngboard. Method One Japanese elte female dver from Tenr Unversty Dvng Team, Japan, subject YM., heght 157 em, weght 50.0 kg, age 18 wth nne years of experence was the subject of the study. She performed forward and reverse dve exercses on a 1 meter sprngboard. She won successve all Japan women's sprngboard dvng champonshps from 1985 to Flms were taken by a Photo-soncs 16 mm camera. The camera loaded wth Fujcolor Reversal Flm (ASA 500), was postoned n the pool area 20 m from the far board. The shutter factor was and the Angeneux zoom lens was set at ts maxmum aperture of f/3. The camera operated at 100 fps durng the exercse. The flm was analyzed wth NAC mcrocomputer and dgtzer for knematc data from whch to generate the dagram of contnuous form, orbt, graph of angle changes and dagram ofhurdle step and take-off patterns for each dvng performance. Results The results fell nto 4 major phases for the forward dve and reverse dve, respectvely. They were as follows: (a) From last contact wth the hurdle support foot to peak of flght. (b) From peak of flght to ntal contact wth both feet at take off. Cc) From maxmum depresson of board to fnal contact wth both feet at take-off. Cd) From maxmum depresson of board to fnal contact wth both feet at take-off. (Fgure 1). 126

3 ( ) tttt~~~~~ ~ ~~11 ~ --A-_.~.-~~ ;d~-~-:-p- 6. t~}~~t~t~~ ~~~1 k ~ ~ ~ hurdl. st<p_6~ As for phase A, there was lttle dfference between the forward dve and the reverse dve. As for phase B, the arms n the forward dve were brought down earler than those of reverse. The forward dve seems to have started the arm-swng earler than the reverse dve to set the ann for 127

4 forward rotaton at take-off. The dfference between the arm postons n the forward and reverse dves at ntal contact, wth both feet postoned for take-off s shown n Fgure 2. fgure2: Dagrams of temporal form at ntal contact wth both feet at take-off (left) and maxmum depresson of board (rght) n forward fgure (---). and reverse fgure ( ). On the average, the shoulder angle, as determned by the segmental end ponts of the rght wrst, shoulder and greater trochanter, showed that the reverse had a larger angle than the forward (49.4 vs 25.2 degrees). (Table 1, Fgure 3). Durng phase C, the phsae from board contact to total depresson, the forward-arm-swng began earler and moved hgher, for the forward dve when compared to the reverse dve (Fgure 2). On the average, the shoulder angle at maxmum board depresson demonstrated a larger angle for the reverse dve as compared to the forward dve (238.7 vs degrees) (Table 1, Fgure 3). Elbow angle, as determned by the segmental end ponts ofthe rght wrst, elbow and shoulder, also determned, that the reverse dve produced a larger angle than the forward dve (144.8 vs degrees) Table 1, Fgure 3). Snce the forward dve always demonstrated a smaller angle durng ths phase, t s suggested that the range of forward arm-swng should be smaller for ths dve than for the reverse dve. 128

5 As for phase D, although the reverse dve had a larger elbow angle durng phase C, the forward dve produced a larger elbow angle durng phase D than dd the reverse dve at fnal contact durng takeoff (173.8 vs degrees) (Table 1, Fgure 3). n the forward dve, arm-swng was smaller before the board recol; after that pont, t became greater for forward rotaton. On the other hand, for the reverse dve the arm-swng was greater before board recol and then became smaller after that pont for backward rotaton. Tablel: Angle of shoulder and elbow durng each dve performance, ( )peak of flght at hurdle, (n )ntal contact at takeoff, (m) maxmum depresson of board, (W) fnal contact at take-off. shoulder (degree) elbow (degree) pos ton forward reverse forward reverse () peak of flght at hurdle (n) ntal contact at take-off (D) maxmu," depresson of board ,7 144,8 129

6 ., JbO! ~.., - :;' 270 ~. -;.c ,., ns ~., "., <:» - 0.D 10 GO 0 A R C D h n phase sequtnc:r phase st>qu<.'nct F1gure3: Angle changes of shoulder and elbow durng forward and reverse dve performance, respectvely, n forward fgure (---). and reverse fgure ( ). Concluson Durng the hurdle step of sprng board dvng, the arm-swng pattern of the forward dve dffers from that of the reverse dve. Both of these swng patterns enable the dver to better execute the arborne phases of each dve. Due to ths notceable dfference n swng pattern, the hurdle step and take-off may be dstngushed n each dve. n order to create rotaton durng the forward dve, t s necessary to swng the arms forward as soon as the board begns to recol. Therefore, the dver must be ready whle the board s depressed. For the reverse dve, the arms are swung more quckly durng the latter half ofthe board recol n order to create a backward rotaton so that the dver's body wll not strke the board. As coaches nstruct ther dvers, they may not always understand that the arm swng on appraoch, hurdle step and take-off s dfferent for the forward and reverse dves. These are not qute dstngushable from the arborne phases. t s suggested that coaches could become better nstructors f they understand the specfc components ofthe chan of moton for each dve, ncludng the approach, hurdle step, and the take-off n sprngboard dvng. 130

7 References Mller, DJ. (1974). A comparatve analyss of the take-off employed n sprngboard dves from the forward and reverse groups. Bomechancs, N, Mller, D.l. (1981). Body segment contrbutons offemale athletes to translatonal requrements of non-twstng sprngboard dve take-offs. n the Female Athlete (edted by J. Borms, M. Hebbelnck and A. Venerando). Karger, Basel. Mller, D.. (1984). Bomechancal characterstcs ofthe fnal approach step, hurdle and take-off of elte Amercan sprngboard dvers. Journal ofhuman Movement Studes, 10,