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.