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Rectus Femoris Muscle Composition: Association with Sports
 Performance and Playing Position in Female Soccer Players


 Background Quadriceps muscle plays a relevant role in soccer as its
 function is determinant for sprinting, jumping and striking the ball. Although
 ultrasound demonstrated to be useful in risk of injury prevention and monitoring
 post-injury rehabilitation, no studies analyzed the ultrasound muscle histology
 with sports performance tests. We aimed to analyze the correlation between
 ultrasound findings related to rectus femoris morphology and composition with
 sports performance indicators and to analyze sociodemographic, sports
 performance and ultrasound differences according to playing position.
 Methods An observational study was conducted at the CFF OLYMPIA soccer
 club (Madrid, Spain). Twenty-two semi-professional female soccer players were
 enrolled in this study. Sociodemographic data, bilateral ultrasound measurements
 of the rectus femoris muscle and sports performance tests (Counter Movement Jump
 -CMJ-, The Sprint Repeat Ability -SRA-, and one Repetition Maximum -1RM-) were
 collected.
 Results No correlations between ultrasound imaging and sports performance
 indicators were found. Significant correlations between cross-sectional area and
 perimeter with age (p<0.05) and fatty infiltration with body mass index
 and tight perimeter (p<0.05) were seen. No muscle ultrasound morphology
 or quality differences were found between the playing positions
 (p>0.05). Finally, most of the functional tests showed no
 between-position differences (except SRA between goalkeepers and attackers).
 Conclusion Although muscle morphology and quality are associated with
 demographic features, US should not be used as a predictor of sports performance
 in female football players since no association between US and sports
 performance were observed. Similar US and functional test scores were obtained
 among the different playing positions.