Oyama Sakiko, Myers Joseph B, Blackburn J Troy, Colman Eli C
University of North Carolina at Chapel Hill, 25799-8700, USA.
Clin Biomech (Bristol). 2011 Feb;26(2):130-5. doi: 10.1016/j.clinbiomech.2010.09.018. Epub 2010 Oct 20.
Repetitive eccentric loading results in muscle damage and subsequent changes in muscle stiffness and edema accumulation, which manifest as reduced joint range of motion and increased muscle cross-sectional area. The purpose of the study was to evaluate changes in shoulder range of motion and the infraspinatus cross-sectional area with repetitive eccentric contraction.
Twenty physically active participants performed 9 sets of 25 repetitions of eccentric external rotator contractions. The ultrasonographic measurement of the infraspinatus cross-sectional area, and shoulder internal/external rotation and horizontal adduction range of motion were measured before, immediately after, and 24h after the intervention.
Infraspinatus cross-sectional area significantly increased from baseline immediately after exercise (P<0.001), and remained elevated from baseline at the 24-hour follow up (P<0.001). Internal rotation and horizontal adduction range of motion did not change significantly between baseline and post-exercise (P>0.05), but were significantly decreased at the 24-hour follow up from the baseline (internal rotation: P<0.001, horizontal adduction: P<0.001) and the immediate post-exercise (internal rotation: P=1.012, horizontal adduction: P=0.016).
These changes observed after the eccentric contractions may have implications for injury development in pitchers, because 1) the infraspinatus endures repetitive eccentric loading with pitching and 2) decreased internal rotation and horizontal adduction range of motion have been linked to upper extremity injuries. However, since the muscle response after eccentric loading varies by the task and previous exposure to similar stress, future study needs to investigate the time course of recovery of the muscle cross-sectional area and range of motion after pitching in competitive pitchers.
重复性离心负荷会导致肌肉损伤以及随后肌肉僵硬度和水肿积聚的变化，表现为关节活动范围减小和肌肉横截面积增加。本研究的目的是评估重复性离心收缩时肩关节活动范围和冈下肌横截面积的变化。
20名身体活跃的参与者进行了9组，每组25次的离心外旋收缩。在干预前、干预后即刻和干预后24小时测量冈下肌横截面积、肩关节内/外旋和水平内收活动范围。
运动后即刻冈下肌横截面积较基线显著增加（P<0.001），在24小时随访时仍高于基线水平（P<0.001）。内旋和水平内收活动范围在基线和运动后之间无显著变化（P>0.05），但在24小时随访时较基线（内旋：P<0.001，水平内收：P<0.001）和运动后即刻（内旋：P=1.012，水平内收：P=0.016）显著减小。
离心收缩后观察到的这些变化可能对投手的损伤发展有影响，因为1）冈下肌在投球时承受重复性离心负荷，2）内旋和水平内收活动范围减小与上肢损伤有关。然而，由于离心负荷后的肌肉反应因任务和既往类似应激暴露情况而异，未来研究需要调查竞技投手投球后肌肉横截面积和活动范围的恢复时间进程。
