International Biomechanics最新文献_第9页

Electromyographic analysis of the upper extremity in water polo players during water polo shots 水球运动员击球时上肢肌电图分析

International Biomechanics Pub Date : 2014-01-01 DOI: 10.1080/23335432.2014.976591

M. Yaghoubi, A. M. E. Moghadam, M. Khalilzadeh, S. Shultz

{"title":"Electromyographic analysis of the upper extremity in water polo players during water polo shots","authors":"M. Yaghoubi, A. M. E. Moghadam, M. Khalilzadeh, S. Shultz","doi":"10.1080/23335432.2014.976591","DOIUrl":"https://doi.org/10.1080/23335432.2014.976591","url":null,"abstract":"The purpose of this study is to understand electromyographic parameters of selected shoulder and arm muscles in water polo shots. The study was carried out with a group of 12 water polo players. Signals were recorded by surface electromyography (EMG) from the pectoralis major (PM), anterior deltoid (AD) and middle deltoid (MD), biceps brachii (BB), triceps brachii (TB), and wrist flexor (WF) muscles. The average and standard deviation of the normalized electrical activity and duration of the muscles were determined during four different water polo shots in water polo players. Post hoc analysis among muscles revealed that PM and AD showed significantly different amplitude values among water polo shots. Because the PM and AD must relax to perform the horizontal abduction necessary in the backhand shot, the amplitude was significantly lower than during overhead, push, or penalty shots. Similarly, the push shot requires elbow extension of a horizontally adducted and internally rotated shoulder; therefore, the AD has greater amplitude during this shot and TB was activated for longer periods of shots required for the elbow extension. There was little difference observed in WF and BB. Thus, this result suggests that these muscles played a similar role during penalty, overhead, and push shots. Therefore, coaches should emphasize the strength, endurance, and flexibility training of the PM and AD that may improve shooting velocity. However, the stabilizing role of the BB and TB is an important factor for overall performance and should also be considered.","PeriodicalId":52124,"journal":{"name":"International Biomechanics","volume":"1 1","pages":"15 - 20"},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/23335432.2014.976591","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60098260","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 5

Biomechanical evolution of the Tkachev on uneven bars in female gymnastics 女子体操高低杠Tkachev的生物力学演化

International Biomechanics Pub Date : 2014-01-01 DOI: 10.1080/23310472.2014.983165

G. Irwin, T. Exell, Michelle L. Manning, D. Kerwin

{"title":"Biomechanical evolution of the Tkachev on uneven bars in female gymnastics","authors":"G. Irwin, T. Exell, Michelle L. Manning, D. Kerwin","doi":"10.1080/23310472.2014.983165","DOIUrl":"https://doi.org/10.1080/23310472.2014.983165","url":null,"abstract":"The development of joint kinematics and kinetics is fundamental to the successful performance of complex flight skills in gymnastics bar routines. Biomechanical understanding of these skills can provide coaches and scientists with key information to make training safe and effective. The Tkachev is a complex and popular gymnastics skill with many different variations. Recently, a new version has been performed, which has become popular with elite female performers. This study examined the key biomechanical characteristics of this skill and contrasted these to the earlier versions reported. Elite female gymnasts (n = 5) were recorded and manually digitised using twin video cameras (50 Hz) at the 2007 World Gymnastics Championships. Three-dimensional (3D) DLT was used to reconstruct the real world coordinates. Individualised inertia characteristics were calculated and used to determine mass centre kinematics. Inverse dynamics analysis was used to calculate joint kinetics at the hips and shoulders from the known values at the toes. The results of this study showed an increased flight time and rotational capacity during the aerial phase for the toe-on Tkachev, as well as a more simple movement pattern and joint kinetic demand with single power impulses at the hips and shoulders compared with previous versions. The key finding of this study was that the toe-on version appeared to be less physically demanding than that the inward and outward techniques, and provide the opportunity to perform more complex aerial phase body positions. These results can help coaches to physically prepare their gymnasts and biomechanists in terms of understanding the demands of these skills.","PeriodicalId":52124,"journal":{"name":"International Biomechanics","volume":"220 1","pages":"21 - 28"},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/23310472.2014.983165","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60067282","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 4

A stochastic structural reliability model explains rotator cuff repair retears 一个随机结构可靠性模型解释了肩袖修复损伤

International Biomechanics Pub Date : 2014-01-01 DOI: 10.1080/23310472.2014.983166

D. M. Donnell, Jessica L. Seidelman, C. Mendias, B. Miller, J. Carpenter, R. Hughes

{"title":"A stochastic structural reliability model explains rotator cuff repair retears","authors":"D. M. Donnell, Jessica L. Seidelman, C. Mendias, B. Miller, J. Carpenter, R. Hughes","doi":"10.1080/23310472.2014.983166","DOIUrl":"https://doi.org/10.1080/23310472.2014.983166","url":null,"abstract":"High rates of tendon retear following surgical repair of large rotator cuff tears have been reported. This study developed a probabilistic structural reliability model of retear with potential to guide quality improvement interventions. A probabilistic biomechanical model of survivorship from a recurrent tear, based on structural reliability and Markov processes, treated the capacity of the surgical repair to withstand tensile loading and the load applied by the supraspinatus muscle as independent lognormally distributed random variables. For a repair to remain intact at the end of the tth day, it had to remain intact on days 0, … , t − 1. After retear was predicted to occur, that repair remained torn in the model. The model predicted two-year survival of 75.7%, which is within the 95% confidence interval of the Kaplan–Meier for data reported by others. The model’s demonstrated prediction of retear can be used for improving repair survival: lowering the variance in both repair strength and in post-operative supraspinatus muscle loading is an effective method for lowering the retear rate. Variance reduction alone may be an effective way to improve surgical treatment of this disorder.","PeriodicalId":52124,"journal":{"name":"International Biomechanics","volume":"1 1","pages":"29 - 35"},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/23310472.2014.983166","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60067292","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 4

Prediction of impact force in sideways fall by image-based subject-specific dynamics model 基于图像的受试者特定动力学模型预测侧身坠落的冲击力

International Biomechanics Pub Date : 2014-01-01 DOI: 10.1080/23310472.2014.975745

Yunhua Luo, M. Nasiri Sarvi, Pei-dong Sun, W. Leslie, J. Ouyang

{"title":"Prediction of impact force in sideways fall by image-based subject-specific dynamics model","authors":"Yunhua Luo, M. Nasiri Sarvi, Pei-dong Sun, W. Leslie, J. Ouyang","doi":"10.1080/23310472.2014.975745","DOIUrl":"https://doi.org/10.1080/23310472.2014.975745","url":null,"abstract":"The impact force applied to the greater trochanter during sideways fall is a critical factor for determining whether or not a hip fracture would occur. However, the impact force is subject-dependent as it is related to the subject’s anthropometric parameters and the kinematic variables in fall. It cannot be accurately predicted by the currently available dynamics models. We developed and validated a method for constructing subject-specific dynamics models to more accurately predict the impact force. The anthropometric parameters required in the model were obtained from the subject’s whole body DXA (dual energy X-ray absorptiometry) image. The subject-specific dynamics models were then validated by protected fall tests using young volunteers. The effects of anthropometric parameters on the impact force were investigated using 90 clinical DXA images obtained from a local osteoporosis clinic center. The impact forces predicted by subject-specific dynamics models had much better agreement with the experimental data, compared with those predicted by the existing empirical functions. The parametric study results indicated that although body weight and height are the dominant parameters affecting the impact force, other parameters such as the hip vertical velocity before impact also have considerable effects. This finding suggests that the existing empirical functions that only consider body weight and height may not be able to accurately predict the impact force. As whole body DXA images are readily available in osteoporosis clinic centers, the proposed method may have potential applications in the clinic to improve the assessment of fall-induced hip fracture risk.","PeriodicalId":52124,"journal":{"name":"International Biomechanics","volume":"1 1","pages":"1 - 14"},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/23310472.2014.975745","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60067730","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 22