The relationship between muscle cross-sectional area and strength in various isokinetic movements among soccer players

Abstract

The aim of the present study was to examine the relationships between muscle cross-sectional area (CSA) and muscular strength in terms of knee extension and flexion, hip extension and flexion, and hip abduction and adduction among well-trained soccer players. Fourteen university soccer players participated in the study, who had previously been divided into two groups based on ability (Group A: above-average ability; Group B: average ability). Maximal isokinetic and concentric muscular strength was measured in knee extension/flexion, hip extension/flexion and hip abduction/adduction using an isokinetic dynamometer at 1.57 and 4.19 rad·s^?1 (3.14 rad·s^?1) in both the dominant and non-dominant leg. The CSAs of the thigh, gluteus muscles and iliopsoas muscles were calculated based on magnetic resonance imaging. There was no significant difference between the two groups in muscle CSA and isokinetic strength. Although there were some statistically significant differences between the dominant and non-dominant leg in terms of CSA and strength (P<0.05–0.01), these were small and negligible. Apart from a non-significant relationship between the CSAs of the adductor muscles and hip adductor strength (r<0.26, n.s.), the CSA of the other muscle groups correlated with maximal isokinetic strength (r=0.38–0.64, P<0.05). These results suggest that no difference in muscle characteristics (in terms of muscle CSA and strength) was apparent among well-trained soccer players, even between the dominant and non-dominant leg. There is also a case that the anatomical function of a single (or group of) muscle(s) may not be reflected by the strength—CSA relationship depending on the movements (such as hip adduction-adductor muscle CSA). Thus, further studies are required to develop methods to assess neuromuscular function in relation to muscle morphology among soccer players.     

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PBL教学模式在口腔颌面医学影像诊断学的应用

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Techniques in X-ray astronomy

The excellent X-ray images produced by X-ray telescopes require the use of detectors with imaging capability at the focal plane of the telescopes. In this concluding part of the article on experimental techniques in X-ray astronomy, I describe many X-ray detectors that have been used over the years. These can broadly be classified into two physical types: non-dispersive and dispersive. Traditionally the simple non-dispersive types have been used extensively in X-ray astronomy. The advancement of solid state technologies, cryogenics, and the quality of X-ray imaging has led to many new detectors of both types. Both the traditional and the new types of detectors are described briefly here with emphasis on principles and some technical details. Kulinder Pal Singh is in the Department of Astronomy and Astrophysics of the Tata Institute of Fundamental Research, Mumbai. His primary fields of research are X-ray studies of hot plasmas in stars, supernova remnants, galaxies, intergalactic medium in clusters of galaxies, active galactic nuclei, cataclysmic variables and X-ray binaries. He is leading the development of a soft X-ray imaging telescope for the ASTROSAT mission to be launched by India in 2007–2008. Part 1. Imaging Telescopes,Resonance, Vol. 10, No. 5, pp. 15–23, 2005.