Biomechanics and Medicine in Swimming XI

More documents

Recommendations

Info

considers the effects due to displacement of water in addition to repulsive effects. The latter are not neglected but qualified. Humans can perform well in an aquatic space without knowing the details of flow physics. It is a different case however when instructors or coaches are not well informed about the relevancy of the interaction of limbs and water-mass and its reaction. In particular the illiteracy of the momentum aspect, only about ten papers in 36 years of the Conference Series of Biomechanics and Medicine of Swimming have handled this topic, is not helpful. The water related view also tackles the terminology of rules of stroking written for the referees in swimming. This terminology still uses the concept of pulling and pushing arms, whereas e.g. the BMS conference series revealed that sculling actions of the hands dominate all strokes. Of course each expert is free to select any terminology. But a more appropriate terminology supports the mental representation of strokes required to execute and control movements. conclusIons The increase of knowledge of effects of ASA in the last decade is remarkable and resembles a change in paradigm. The traditional paradigm is body orientated and concentrates on the biomechanical aspects of body motion. ASA related sports like Recreational swimming, Finswimming, Triathlon, Scuba-diving or Water-exercises seem still to be far from the water related view, still relying on the established u²-law of resistance. This approach is an acceptable pedagogical view, searching for best solutions as to how to teach swimming and stroking correctly. Bridging the gap and approaching a water related view including unsteady features of flow seems to be difficult. The vortex-ring like structure created by hand-action demands a turning around action of the hand, a kind of supination or pronation, during the period of underwater action. Since all activities performed in aquatic space will face more or less the same conditions, it is concluded that unsteady flow physics should become the basis of further research, independently of biomechanical or physiological issues. This continued research needs also to be phrased in terms permitting it to be accepted by practitioners. reFerences Berger, M. (1995). Force generation and efficiency in front crawl swimming. Thesis Vrije Universiteit, Amsterdam. Counsilman, J. E. (1968). The Science of Swimming. Prentice Hall. New Jersey. Counsilman, J. E. & Counsilman, B (1994). The New Science of Swimming. Prentice Hall. New Jersey. Matsuuchi, K, Miwa, T., Nomura, T., Sakakibara, J., Shintan, H.. & Ungerechts, B.E, (2004). Unsteady flow measurement around a human hand in swimming using PIV. In: E v Praagh, J Coudert, N Fellmann, P Duché (eds.) Proceedings of 9 th Annual Congress of the ECSS, Clermont-Ferrand, 274. Tilborgh van, L., Willems E.J, & Persyn U. (1988). Estimation of breaststroke propulsion and resistance-resultant impulses from film analyses. In: B.E. Ungerechts, K. Wilke and K. Reischle (eds.), Swimming Science V, Human Kinetics Publishers, Champaign, IL: 67- 71. Ungerechts, B.E., (1988). The relation of peak body acceleration and phases of movements in swimming. In: B.E. Ungerechts, K. Wilke and K. Reischle (eds.), Swimming Science V, Human Kinetics Publishers, Champaign, IL, 61-66. Ungerechts, B.E., (1992). The interrelationship of hydrodynamical forces and swimming speed in breaststroke. In: D. MacLaren, T. Reilly & A. Lees (eds.), Biomechanics and Medicine in Swimming -Swimming Science VI-. E. & FN Spon, London:69 - 73. Ungerechts, B. E. & Klauck J. (2006). Consequences of non-stationary flow effects for functional attribution of swimming strokes. In: J.P. chaPter2.Biomechanics Vilas-Boas, F. Alves, A. Marques (eds.), Biomechanics and Medicine in Swimming X. Portuguese Journal of Sport Sciences, 6, Suppl. 2, 109- 111. AcKnoWledGMents The authors would like to thank Dr. Huub Toussaint from Swimming Research Center Amsterdam, The Netherlands, for valuable information and suggestions to accomplish this paper. 177
BiomechanicsandmedicineinswimmingXi Analysis of Swim Turning, Underwater Gliding and Stroke Resumption Phases in Top Division Swimmers using a Wearable Inertial Sensor Device Vannozzi, G. 1 , donati, M. 1 , Gatta G. 2 & cappozzo, A. 1 1 Department of Human Movement and Sport Sciences, University of Rome “Foro Italico”, Italy 2 Faculty of Exercise and Sport Science, University of Bologna, Italy Improving performance is a difficult task for élite swimmers. The study of turning, underwater gliding and stroke resumption kinematics may lead to the reduction of the relevant durations. Common video analysis is sometimes inadequate to investigate motor tasks. This work aimed at describing the mentioned phases in top division swimmers using a wearable inertial device. Eight élite swimmers were selected so as to cover all the four swimming styles. The device was positioned on the lower trunk and a 50m trial at the maximum velocity was executed. The angular velocity about each axis was post-processed and both time and kinematic parameters were extracted for each phase, characterizing each swimming style. Strength points of the approach are: simple description of the turning kinematics; possibility to extract performance-related parameters; simplicity of use for the operator; the minimal encumber for the athlete. KeY-Words: inertial sensor, angular velocity, turning, kinematics IntroductIon Improving athletic performance is one of the main goals of sport biomechanics, in general, and of swimming research, in particular. This goal is more difficult to obtain as the elite swimming level increases, thus chances for improvement are relatively limited. However, closely examining swimming aspects such as turning, underwater gliding and stroke resumption phases, and investigating how the relevant timing might be optimised for improving the overall swimmer performance, may provide valuable information to the coach. This circumstance was remarked by Lyttle et al. (1999) who stated that “little changes on the turning action performance can imply substantial improvements of the final event time”. The goal of deepening knowledge into the mentioned swimming phase can be obtained if an accurate way to describe the kinematics of the abovementioned swimming phases is made available. Among the mentioned swim phases, turning is one of the most critical to be analysed. Turning mechanics is usually described using force plates embedded in the pool wall (Takahashi et al., 1982), to obtain forces and torques during the push-off phase that follows the rotational phase. Both flip-turns and open turns are complex movements, usually investigated - with great difficulty - using video analysis. In fact, due to the aquatic environment, refraction of the water, as well as actions of several body segments, which are moving in different movement planes (Pereira et al., 2008), it is not rare to experience serious difficulties in tracking the selected skin markers. Moreover, video analysis usually requires a complex instrumental set-up and a massive computational effort to obtain the desired biomechanical quantities. For these reasons, this important phase of a swimming competition is scarcely dealt with in the scientific literature. Following the recent trend of implying wearable inertial devices in human movement analysis, also swimming research recently started to include such sensors in experimental setups. Ohgi and colleagues (2003) used a tri-axial accelerometer positioned on the wrist to carry out a phase segmentation of breaststroke trials. The feasibility of using a 3D accelerometer mounted on the pelvis was demonstrated by Slawson et al. (2008), who succeeded in characterising pelvis linear accelerations in different swimming styles. At this stage of research, the available applications dealt only with linear accelerations and there is no evidence 178 on how the mentioned swimming phases might be characterized using inertial sensor devices. This work aimed at quantitatively describing the swim turning, underwater gliding and stroke resumption phases in top division swimmers using a wearable inertial device composed of a tri-axial accelerometer and gyroscope. This objective entailed the definition of appropriate parameters that could be effectively used by the coach to compare different swimming techniques towards total-time minimisation. Methods Eight elite swimmers (four males and four females) volunteered to participate in the study. The athletes are part of a top division Italian team and were selected so as to cover the four swimming styles (freestyle, backstroke, breaststroke and butterfly). Participants wore the FreeSense device (Sensorize, Italy) which is a wearable measurement instrument equipped with a tri-axial accelerometer and two bi-axial gyroscopes, weighing 93g and fully portable (size: 8.8 x 5.1 x 2.5 cm), allowing to perform the swimming task in the most natural fashion (as depicted in Figure 1). Once water-proofed, the device was incorporated into an elastic (neoprene) belt which was fastened around the participant’s waist, at the dorsal side of the trunk at the fourth lumbar vertebra level. In Fig.1 the device positioning is represented together with the definition of the local reference frame. The device output were three linear accelerations along the three local axes and three angular velocities (ω x , ω y and ω z ) about the same axes. Figure 1: Device positioning on a swimmer low trunk and definition of the local frame of reference. Data were collected with a sampling frequency of 100 Hz and were saved directly on board of the device. A commercial video camera and a chronometer were also used to video-record each trial and to record the relevant time duration (t chr ), respectively. All data collection was performed in a 25m swimming pool. After familiarisation with the instrument, each participant was asked to perform a 50m trial at his/her maximum velocity as during a real competition. In this study, temporal and kinematic parameters were mainly obtained using angular velocities about the three axes of the local frame of reference. For each swimming style, the following parameters were extracted for the different phases: � Gliding phase - duration of first and second lap, respectively t glide25 and t glide50 ; � Stroke phase - duration of first and second lap, respectively t stroke25 and t stroke50 ; � turning phase - duration, t turn ; peaks of angular velocities - pω x , pω y and pω z ; time interval between the main two angular velocity peaks, t pp . The parameter selection procedure is depicted in Figure 2 considering a randomly selected backstroke trial that includes the execution of a flipturn technique. The same procedure was also reported in Figure 3 for a butterfly trial, including an open-turning execution. Even if only angular velocities were used in this paper, similar considerations can be made to extract appropriate parameters from measured local accelerations.
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: Biomechanicsandmedicinein
Page 177: Biomechanicsandmedicinein
Page 217 and 218: average VO2 measured during resting
Page 221 and 222: Fourteen highly trained male swimme
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:
Page 293 and 294:
Page 295 and 296:
Page 297 and 298:
Page 299 and 300:
-ARM * 5 Biomechanicsandmedic
Page 301 and 302:
Page 303 and 304:
Page 305 and 306:
Page 307 and 308:
Page 309 and 310:
Page 311 and 312:
Page 313 and 314:
Page 315 and 316:
Page 317 and 318:
Page 319 and 320:
• Without restriction; • Blinde
Page 321 and 322:
Page 323 and 324:
Page 325 and 326:
Page 327 and 328:
Page 329 and 330:
Page 331 and 332:
Page 333 and 334:
Page 335 and 336:
Page 337 and 338:
Page 339 and 340:
Page 341 and 342:
Page 343 and 344:
Page 345 and 346:
Page 347 and 348:
Page 349 and 350:
Page 351 and 352:
Page 353 and 354:
Page 355 and 356:
Page 357 and 358:
Page 359 and 360:
etween experimental groups and cont
Page 361 and 362:
Page 363 and 364:
Page 365 and 366:
Page 367 and 368:
Page 369 and 370:
Page 371 and 372:
Page 373 and 374:
Page 375 and 376:
Page 377 and 378:
Page 379 and 380:
Page 381 and 382:
Page 383 and 384:
Page 385 and 386:
Page 387 and 388:
Page 389 and 390:
Page 391:
Pahlen Norge AS Pahlen Norge AS Cha
show all

Biomechanics and Medicine in Swimming XI

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?