Abstract
The arm-swing motion is important for coordinated lower limb movement during a fast sprint and is composed of three-dimensional scapulothoracic and glenohumeral joint motion. Here, we aimed to clarify the role of the scapula during the initiation of a sprint running when sprinter run with high horizontal acceleration. Ten sports-active students participated in four 5-m dashes, with scapular constraint using non-elastic therapy tape (constraint condition) and without scapular constraint (free condition). The sprinting kinematics was assessed by a 16-camera motion capture system. In the constraint condition, the 2-m sprint time was significantly longer than that in the free condition. At the instants of foot-contact and take-off during the first step, no significant difference in the humerothoracic flexion angle was seen between these two conditions. In contrast, at the instants of foot-contact and take-off during the first step, the humerothoracic extension angle in the constraint condition was significantly smaller than that in the free condition. The forward leaning vector angle of center of mass during the first step was significantly greater than that in the constraint condition. Although no significant difference in hip extension and foot forward leaning angles was seen at the instant of foot contact during the first step between the two conditions, at the instant of take-off, the hip extension and foot forward leaning angles in the constraint condition were significantly smaller than those in the free condition. Therefore, scapular behavior in first accelerated running contributes to larger upper- and lower-limb motions and facilitates coordinating whole-body balance for a fast sprint.
Highlights
For a fast sprint running, upper and lower limb movements have to be coordinated (Lockie et al 2003)
Humeral motion relative to the thorax is contributed by scapular motion relative to the thorax and humeral motion relative to the scapula (joints that relate to these motions are defined as humerothoracic, scapulothoracic, and glenohumeral joints, respectively (Codman 1934)
No significant difference in hip extension and foot forward leaning angles was seen at the instant of foot contact during the first step between the two conditions, at the instant of take-off, the hip extension and foot forward leaning angles in the constraint condition were significantly smaller than those in the free condition
Summary
For a fast sprint running, upper and lower limb movements have to be coordinated (Lockie et al 2003). The momentum at horizontal component of the upper arm, forearm and hand (we define these three segments as “arm”) is not directly associated with that of the whole-body center of mass (COM) because the backward- and forward-swinging motions of the arms are in opposite directions and the momentum is cancelled (Hinrichs 1987; Hinrichs et al 1987). The range of motion (ROM) of the scapulothoracic joint is half that of the glenohumeral joint during humerothoracic elevation (Inman et al 1994), and the ROM of the scapulothoracic joint increases according to the movement velocity of the humerothoracic joint (Fayad et al 2006). The flexion and extension angular velocity of the humerothoracic joint is high (approximately 700°/s) (Slawinski et al 2010b), indicating that the ROM of the scapulothoracic joint is important during sprint running to enhance the ROM of the humerothoracic joint and the sprint speed. The scapular behavior would be important for fast sprinting in first accelerated running
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