Strength imbalance between internal and external rotators of the shoulder may increase the risk of sports injury. Research on whether isokinetic eccentric training (IET) could enhance the strength ratio and improve neuromuscular control of shoulder rotators has important implications for injury prevention.

To investigate the effects of IET on strength ratio and neuromuscular control of internal and external rotators of the shoulder in healthy young people.

From December 2020 to November 2021, 32 healthy young people were recruited as the subjects from Zhongshan Hospital, Fudan University, and they were randomly divided into an experimental group (n=16) and a control group (n=16) . The experimental group received IET for 4 weeks, while the control group received continuous passive motion training for 4 weeks (twice a week) . A Biodex System 4 Pro Dynamometer (Biodex Medical Systems Inc., USA) was used to implement intervention training on internal and external rotators of the dominant shoulder, which was conducted under the velocity of 60 (°) /s, 120 (°) /s and 180 (°) /s, respectively. The functional ratio (FR) , acceleration time (AT) and time to peak torque (TPT) of internal and external rotators of the shoulder of the two groups were evaluated, and compared at 1 week before the intervention and 1 week after the end of the intervention, respectively.

All subjects in the experimental group completed 4 weeks of training and evaluation, whereas 2 subjects in the control group dropped out. Ultimately, data of 30 subjects were involved in the statistical analysis. Under the velocity of 60 (°) /s, 120 (°) /s, FRs were significantly higher in the experimental group compared with the control group after the intervention (P<0.001) . Meanwhile, FRs in the experimental group were significantly higher during post-intervention evaluation compared with pre-intervention evaluation (paired samples t-test: t_{60 (°) /s}=-7.881, P<0.001; t_{120 (°) /s}=-6.563, P<0.001) . ATs of external and internal rotators were significantly lower in the experimental group compared with the control group after the intervention (P<0.05) . Moreover, ATs of external rotators in the experimental group were significantly lower during post-intervention evaluation compared with pre-intervention evaluation (paired samples t-test: t_{60 (°) /s}=2.383, P<0.05; t_{120 (°) /s}=2.849, P<0.05) , and ATs of internal rotators in this group were also significantly lower during post-intervention evaluation compared with pre-intervention evaluation (paired samples t-test: t_{60 (°) /s}=3.138, P<0.05; t_{120 (°) /s}=2.839, P<0.05) . TPTs of external and internal rotators were significantly lower in the experimental group compared with the control group after the intervention (P<0.05) .

IET can enhance the strength ratio of internal and external rotators, remain the dynamic stabilization of the shoulder and improve neuromuscular control, which may reduce the risk of sports injury.

肩关节内外旋肌肌力失衡会增加肩部运动损伤的风险，研究等速离心训练（IET）能否提高肌力平衡并改善神经肌肉控制能力具有重要的损伤预防意义。

探讨IET对健康青年人肩关节内外旋肌的肌力平衡及神经肌肉控制能力的影响。

2020年12月至2021年11月在复旦大学附属中山医院招募32例健康青年志愿者为研究对象，随机将其分为试验组（n=16）和对照组（n=16）。试验组接受4周IET，对照组接受4周连续被动运动训练（2次/周）。采用Biodex System 4 Pro多关节等速肌力测试与训练系统（美国Biodex公司）对两组研究对象的优势侧肩关节内、外旋肌群进行训练干预，分别在60（°）/s、120（°）/s速度下进行，干预前1周、干预结束后1周对两组肩关节内外旋肌的功能性比率（FR）、加速时间（AT）和达峰力矩时间（TPT）进行评估并比较。

试验组全部完成了4周的训练干预和评估，对照组2例中途退出。最终共30例研究对象数据纳入统计学分析。在60（°）/s和120（°）/s速度下，试验组干预后FR高于对照组（P<0.001），试验组干预后FR高于干预前（配对t检验：t_60（°）/s=-7.881，P<0.001；t_{120（°）/s}=-6.563，P<0.001）；试验组外旋肌、内旋肌干预后AT低于对照组（P<0.05），试验组外旋肌干预后AT低于干预前（配对t检验：t_60（°）/s=2.383，P<0.05；t_{120（°）/s}=2.849，P<0.05），试验组内旋肌干预后AT低于干预前（配对t检验：t_60（°）/s=3.138，P<0.05；t_{120（°）/s}=2.839，P<0.05）；试验组外旋肌、内旋肌干预后TPT低于对照组（P<0.05）。

IET能够提高肩关节内外旋肌的肌力平衡，保持肩关节的动态稳定，并能改善神经肌肉控制能力，以此可能会降低运动损伤的风险。