title: Effects of forward trunk lean on hamstring muscle kinematics during sprinting.
abstract: This study aimed to investigate the effects of forward trunk lean on hamstring muscle kinematics during sprinting. Eight male sprinters performed maximal-effort sprints in two trunk positions: forward lean and upright. A three-dimensional musculoskeletal model was used to compute the musculotendon lengths and velocity of the biceps femoris long head, semitendinosus, and semimembranosus muscles during the sprinting gait cycle. The musculotendon lengths of all the three hamstring muscles at foot strike and toe-off were significantly greater during the forward trunk lean sprint than during the upright trunk sprint. In addition, a positive peak musculotendon lengthening velocity was observed in the biceps femoris long head and semimembranosus muscles during the late stance phase, and musculotendon lengths at that instant were significantly greater during the forward trunk lean sprint than during the upright trunk sprint. The present study provides significant evidence that a potential for hamstring muscle strain injury involving forward trunk lean sprinting would exist during the stance phase. The results also indicate that the biceps femoris long head and semimembranosus muscles are stretched during forward trunk lean sprinting while contracting eccentrically in the late stance phase; thus, the elongation load on these muscles could be increased.
authors.affiliation: a The Japan Society for the Promotion of Science , Tokyo , Japan.
authors.forename: Ayako
authors.initials: A
authors.lastname: Higashihara
authors.forename: Yasuharu
authors.initials: Y
authors.lastname: Nagano
authors.forename: Kazumasa
authors.initials: K
authors.lastname: Takahashi
authors.forename: Toru
authors.initials: T
authors.lastname: Fukubayashi
mesh_terms: D001696:Biomechanical Phenomena; D006615:Hip / Q000502:physiology; D006801:Humans; D007717:Knee / Q000502:physiology; D008297:Male; D018482:Muscle, Skeletal / Q000293:injuries / Q000502:physiology*; D010388:Pelvis / Q000502:physiology; D011187:Posture / Q000502:physiology*; D012307:Risk Factors; D012420:Running / Q000293:injuries / Q000502:physiology*; D013848:Thigh; D013996:Time and Motion Studies; D060726:Torso / Q000502:physiology*; D055815:Young Adult
keywords: forward trunk lean sprint; hamstring muscles; muscle strain injury; musculotendon length