title: Lower muscle co-contraction in flutter kicking for competitive swimmers.
abstract: The purpose of this study was to examine the difference in muscle activation pattern and co-contraction of the rectus and biceps femoris in flutter-kick swimming between competitive and recreational swimmers, to better understand the mechanism of repetitive kicking movements during swimming. Ten competitive and 10 recreational swimmers swam using flutter kicks at three different velocities (100%, 90%, and 80% of their maximal velocity) in a swimming flume. Surface electromyographic signals (EMG) were obtained from the rectus (RF) and biceps femoris (BF), and lower limb kinematic data were obtained at the same time. The beginning and ending of one kick cycle was defined as when the right lateral malleolus reached its highest position in the vertical axis. The offset timing of muscle activation of RF in the recreational swimmers was significantly later at all velocities than in the competitive swimmers (47-48% and 26-33% of kick time of one cycle for recreational and competitive swimmers, respectively), although the kinematic data and other activation timing of RF and BF did not differ between groups. A higher integrated EMG of RF during hip extension and knee extension induced a higher level of muscle co-contraction between RF and BF in the recreational swimmers. These results suggest that long-term competitive swimming training can induce an effective muscle activation pattern in the upper legs.
authors.affiliation: Department of Sports Sciences, Japan Institute of Sports Sciences, Tokyo, Japan. Electronic address: damatsu0512@gmail.com.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Matsuda
authors.affiliation: Department of Sports and Health Sciences, Aichi Shukutoku University, Aichi, Japan.
authors.forename: Masami
authors.initials: M
authors.lastname: Hirano
authors.affiliation: Department of Nutritional Science, National Institutes of Biomedical Innovation, Health and Nutrition, Tokyo, Japan.
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Yamada
authors.affiliation: Graduate School of Education, Osaka Kyoiku University, Osaka, Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Ikuta
authors.affiliation: Graduate School of Science and Technology, Kyoto Institute of Technology, Kyoto, Japan.
authors.forename: Teruo
authors.initials: T
authors.lastname: Nomura
authors.affiliation: Fukuoka University Institute for Physical Activity, Faculty of Sports and Health Science, Fukuoka University, Fukuoka, Japan; Central Research Institute for Physical Activity, Fukuoka University, Fukuoka, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Tanaka
authors.affiliation: Faculty of Health and Well-being, Kansai University, Osaka, Japan.
authors.forename: Shingo
authors.initials: S
authors.lastname: Oda
mesh_terms: D001696:Biomechanical Phenomena / Q000502:physiology*; D003163:Competitive Behavior / Q000502:physiology*; D004576:Electromyography; D005260:Female; D006801:Humans; D007866:Leg / Q000502:physiology; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D052097:Quadriceps Muscle / Q000502:physiology; D013550:Swimming / Q000502:physiology*; D055815:Young Adult
keywords: EMG; Front crawl; Lower limb; Proficiency