Biomechanics and Medicine in Swimming XI

More documents

Recommendations

Info

The Effect of a Target Sound Made by a Model Swimmer’s Dolphin Kick Movement on Another Swimmer’s Dolphin Kick Performance shimojo, h. 1 , Ichikawa, h. 2 , tsubakimoto, s. 1 , takagi, h. 1 1 Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba City, Japan 2 Department of Sports Information, Japan Institute of Sports Sciences, Tokyo, Japan The aim of this study was to determine the effect of a target sound made by a model swimmer’s dolphin kick movement on another swimmer’s dolphin kick performance. Fifteen competitive swimmers participated in this study. Subjects were required to swim using a dolphin kick while listening to the target sound as closely as possible. The aim of the task was to determine whether the timing and displacement of their dolphin kick would change, and the degree to which the change would be retained without the sound. After swimming with sound, subjects experienced a decrease in timing error relative to their performance without sound for up to 300 s, but displacement error did not decrease significantly. The results also suggested that with auditory models, which have been particularly effective for timing patterns, it would be hard to recognize displacement differences. Key words: dolphin kick, motor learning, auditory model IntroductIon In swimming training, the swimmer must enhance power and endurance for good performance, which involves efficient movement. Such high performance movement must be achieved through effective motor learning. Many motor learning and motor control studies were conducted in sports psychology and neuroscience. Target tracking tasks, require the subject to move a cursor utilizing a mouse to track moving target point on display. The trajectory error of trials was used to evaluate performance. Yamamoto et al. (2007) reported target tracking tasks utilizing an auditory model, where the movement target on display was synchronized with stereo sounds expressing right or left by sound volume control. The subject was required to control the mouse to get close to the moving target following auditory model with the eyes closed. They suggested that the auditory model could be used in real world sports training. Baudry et al. (2006) reported that an auditory concurrent feedback on cyclic movement was effective in motor learning and performance. Wang and Hart (2005) reported that an auditory model that was an effective method to enhance the learning of swimming movement timing in beginner classes. But an auditory model has not been attempted in expert swimmers. If an auditory model could affect motor learning to create the skilled movement required for high performance in competitive swimming, coaches and swimmers could use such a method to enable swimmers to improve each other’s performance in training. The purpose of this study, therefore, was to determine the effect of a target sound produced by a model swimmer’s dolphin kick movement on another swimmer’s dolphin kick performance. Method Fifteen competitive swimmers (ten males and five females) participated in this study. They were aged 22.1 ± 4.7 years and all subjects had more than ten years of experience in competitive swimming and had normal hearing. An informed consent was obtained from all subjects before their participation in this study. Before this study, one model swimmer swam with the dolphin kick in the pool at sub-maximal speed (1 m/s) for getting two-dimensional coordinates by filming. After a single kick phase was chosen, coordinates chaPter5.education,adviceandBiofeedBack of the swimmer’s vertical range were exchanged to relative coordinates (% height). We created a “target sound” that indicating displacement differences expressed as sound frequency scales in the range of 300~900 Hz converted by the coordinates. Because “Concert A” or “Middle A” is the 440 Hz tone that serves as the standard for musical pitch and is used in instrument tuning, the range of 300~900 Hz was adopted with an average of 440Hz for the “target sound”. Prior to this study, it had been confirmed whether the model swimmer could replay the same movement while listening to the target sound in the pretest. After it was explained to subjects what the target sound indicated, the subjects were required to swim with the dolphin kick after a wall push start to a distance of 10m while listening to the target sound, and to “track” the target swimmer’s movement. The task was to swim “tracking” the movement of the target as well as possible. After the normal dolphin kick test that required the subject to swim at 80 % or less effort, there were two tasks. The aim of Task 1 was to see whether difference of sound scale would affect the displacement of a swimmer’s dolphin kick. The 75% range (375~825 Hz) and the 50% range (450~750 Hz) target sound, indicating that the height of toe displacement in the dolphin kick was narrow, were obtained from the target sound. Task 1 was conducted the 75% and the 50% target sound were used randomly for ten trials, and the effect was investigated from differences between pre 1 and post 1 trials with target sound. The aim of Task 2 was to see whether the swimmer’s dolphin kick would retain any improvements without the target sound. Task 2 was conducted with the target sound for ten sessions. The effect was investigated from differences between pre2, post2, post3 (60 s later), post4 (120 s later) and post5 (300 s later) with no sound requiring the subjects to reproduce the same dolphin kick movement as in Task 1. Figure 1 shows the study protocol. Figure 1. Protocol followed in which subjects were required to use the dolphin kick in every trial. Data collection was undertaken in an indoor swimming pool whose depth ranged 1.3 m to 1.8 m. Every trial was recorded using four cameras (TK-C1381 Victor Inc., Japan) through an underwater poolside window. Data sampling set 60 Hz. The two-dimensional coordinates of the swimmers’ vertical toe displacement were obtained by a two-dimensional DLT method using motion analysis software (Frame-DIAS 4, DKH Inc., Japan), and were exchanged to relative coordinates (% height) for comparison with the model swimmer. The sound was generated utilizing underwater speakers (MT-70 Toyoonkyo Corp., Japan) that were synchronized with the underwater cameras. Figure 2 shows the evaluation from data collected. 341
BiomechanicsandmedicineinswimmingXi Figure 2. Experiment setting and evaluation for performance from data collected. Two approaches to evaluation were used. One approach applied the idea of Timing Error (TE). The target cycle time was 0.6 s (i.e. the kick phase time). The TE obtained was compared with the trial cycle time and the target cycle time. The second approach employed Displacement Error (DE). The vertical displacement range of the target dolphin kicks were evaluated on a scale of 0 % to 100 %. DE was evaluated by relative Root Mean Square Error (rRMSE) by the displacement of each kick following Fusco and Crétual (2008). Following auditory perception, there is a delay before humans initiate movement (Charles et al., 2001). The DE evaluation was divided into an upward kick and a downward kick without match time. TE and DE were obtained as: TE (s) = A kick cycle time – the target cycle time (0.6 s) N DE (%) = rRMSE = 1 2 ∑= ei N i 1 The closer that the value of TE and DE were to zero, the closer the movement of the subjects were to the target movement. The mean of TE and DE for all trials were compared using one-way repeated measures ANOVA followed by the Bonferroni multiple comparison. results Task 1: Time differences between target cycle time and subject cycle time on the last five trials and total average was calculated by TE. The result of total average of TE in the normal trial was 0.07 ± 0.03 s, pretest 1 was 0.01 ± 0.01 s and post-test 1 was 0.01 ± 0.01 s. There were significant differences between normal and pre-test 1 (p < .01), normal and post-test 1 (p < .01), but no difference between pre-test 1 and posttest 1. Relative displacement differences between target and subject on last five kick trials and total average was calculated by DE. The result of DE of total average in normal was 14.8 ± 1.39 %, pre-test 1 was 10.74 ± 1.00 % and post-test 1 was 10.87 ± 0.61 %. There were significant differences between normal and pre-test 1 (p < .01), normal and post-test 1 (p < .01), but no difference between pre-test 1 and post-test 1. Figure 3 shows the mean ± standard deviation of TE (left) and DE (right) of the last five dolphin kick trials and the total mean values. 342 TE (s) 0.12 0.10 0.08 0.06 0.04 0.02 0.00 -0.02 -0.04 -0.06 normal TE pre1 TE post1 1 2 3 4 5 total Dolphin kick (cycle) 20.0 18.0 16.0 14.0 12.0 10.0 8.0 6.0 4.0 2.0 0.0 normal DE pre1 DE post1 1 2 3 4 5 Dolphin kick (cycle) total Figure 3. TE (left) and DE (right) shows the mean ± standard deviation of each last five kick of all subjects and the total mean with sound. Fpor statistical significance, please refer to the text. DE (%) Task 2: Time differences between target cycle time and subject cycle time for the last five trials and total average was calculated by TE. The result of TE of total average in pre 2 was 0.02 ± 0.01 s, post 2 was 0.02 ± 0.03 s, post 3 was 0.01 ± 0.02 s, pos 4 was 0.02 ± 0.01 s and post 5 was 0.01 ± 0.02 s. There were no differences between trials. Relative displacement differences between target and subject for the last five trials and total average was calculated by DE. The result of DE of total average in pre 2 was 12.1 ± 0.9 %, post 2 was 12.3 ± 0.9 %, post 3 was 13.0 ± 2.7 %, post 4 was 11.3 ± 1.9 % and post 5 was 10.45 ± 0.6 %. There were significant differences between pre 2 and post 5 (p < .01), post2 and post5 (p < .01), post3 and post5 (p < .05). Figure4 shows the mean of TE (left) and DE (right) of each last five dolphin kick and the total mean values. TE (s) DE (%) 0.12 0.10 0.08 0.06 0.04 0.02 0.00 -0.02 20.0 18.0 16.0 14.0 12.0 10.0 8.0 6.0 4.0 2.0 0.0 TE pre2 TE post2 TE post3 (60s) TE post4 (120s) TE post5 (300s) 1 2 3 4 5 total Dolphin kick (cycle) DE pre2 DE post2 DE post3 (60 s) DE post4 (120 s) DE post5 (300 s) 1 2 3 4 5 total Dolphin kick (cycle) Figure 4. TE (top) and DE (bottom) shows the mean of each last five kick of all subjects and the total mean with sound. ns: no significant difference between trials. * significant difference between trials for multiple comparison (*p < .05, **p < .01).
Page 1 and 2:
Biomechanics and Medicine in Swimmi
Page 3 and 4:
Bibliographic information: Biomecha
Page 5 and 6:
Biomechanicsandmedicinein
Page 7 and 8:
Page 9 and 10:
Page 11 and 12:
Page 13 and 14:
Page 15 and 16:
Page 17 and 18:
Page 19 and 20:
Page 21 and 22:
Page 23 and 24:
Page 25 and 26:
Page 27 and 28:
Page 29 and 30:
Page 31 and 32:
Page 33 and 34:
Page 35 and 36:
Page 37 and 38:
Page 39 and 40:
Page 41 and 42:
Page 43 and 44:
Page 45 and 46:
Page 47 and 48:
Page 49 and 50:
Page 51 and 52:
Page 53 and 54:
Page 55 and 56:
Page 57 and 58:
Page 59 and 60:
Page 61 and 62:
Page 63 and 64:
Page 65 and 66:
Page 67 and 68:
Page 69 and 70:
Page 71 and 72:
Page 73 and 74:
Page 75 and 76:
Page 77 and 78:
Page 79 and 80:
Page 81 and 82:
Figure 1. General biomechanical par
Page 83 and 84:
Page 85 and 86:
Page 87 and 88:
Page 89 and 90:
Page 91 and 92:
Page 93 and 94:
Page 95 and 96:
Page 97 and 98:
Page 99 and 100:
Page 101 and 102:
Page 103 and 104:
Page 105 and 106:
Page 107 and 108:
Page 109 and 110:
Page 111 and 112:
Page 113 and 114:
Page 115 and 116:
Page 117 and 118:
Page 119 and 120:
Page 121 and 122:
Page 123 and 124:
Page 125 and 126:
Page 127 and 128:
Page 129 and 130:
Page 131 and 132:
Page 133 and 134:
Page 135 and 136:
Page 137 and 138:
Page 139 and 140:
Page 141 and 142:
Page 143 and 144:
Page 145 and 146:
Page 147 and 148:
Page 149 and 150:
Page 151 and 152:
Page 153 and 154:
Page 155 and 156:
Page 157 and 158:
Page 159 and 160:
Page 161 and 162:
Page 163 and 164:
Page 165 and 166:
Page 167 and 168:
Page 169 and 170:
Page 171 and 172:
Page 173 and 174:
Page 175 and 176:
Page 177 and 178:
Page 179 and 180:
Page 181 and 182:
Page 183 and 184:
Page 185 and 186:
Page 187 and 188:
Page 189 and 190:
Page 191 and 192:
Page 193 and 194:
Page 195 and 196:
Page 197 and 198:
Page 199 and 200:
Page 201 and 202:
Page 203 and 204:
Page 205 and 206:
Page 207 and 208:
Page 209 and 210:
Page 211 and 212:
Page 213 and 214:
Page 215 and 216:
Page 217 and 218:
average VO2 measured during resting
Page 219 and 220:
Page 221 and 222:
Fourteen highly trained male swimme
Page 223 and 224:
Page 225 and 226:
Page 227 and 228:
Page 229 and 230:
Page 231 and 232:
Page 233 and 234:
Page 235 and 236:
Page 237 and 238:
Page 239 and 240:
Page 241 and 242:
Page 243 and 244:
Page 245 and 246:
Page 247 and 248:
Page 249 and 250:
Page 251 and 252:
Page 253 and 254:
Page 255 and 256:
Page 257 and 258:
Page 259 and 260:
Page 261 and 262:
Page 263 and 264:
Page 265 and 266:
Page 267 and 268:
Figure 2. Repeatability of the LTin
Page 269 and 270:
Page 271 and 272:
Page 273 and 274:
Page 275 and 276:
Page 277 and 278:
Page 279 and 280:
Page 281 and 282:
Page 283 and 284:
Page 285 and 286:
Page 287 and 288:
Page 289 and 290:
Page 291 and 292: Biomechanicsandmedicinein
Page 299 and 300: -ARM * 5 Biomechanicsandmedic
Page 319 and 320: • Without restriction; • Blinde
Page 341: Biomechanicsandmedicinein
Page 359 and 360: etween experimental groups and cont
Page 391: Pahlen Norge AS Pahlen Norge AS Cha
show all

Biomechanics and Medicine in Swimming XI

Create successful ePaper yourself

Delete template?

Save as template?