The Kinematics And Electromyography Analysis And Rehabilitation Research On Table Tennis Athletes With Scapular Muscle Imbalance

Objective:Using 3-diamension motion analysis and surface electromyography (SEMG) systems, the athletes of Chinese table tennis national team with or without scapular muscle imbalance and healthy young men were compared. The purpose of this study is to identify whether the athletes with shoulder pain had scapular muscle imbalance(SMI) and subacromial impingement syndrome(SAIS); to analysis the unique kinematics and SEMG characteristics of athletes with SMI; to explore the relationship between SMI and SAIS; to evaluate the effect of rehabilitation protocols aimed at SMI of athletes, and then to formulate the general evaluation strategy on SMI and rehabilitation effect of table tennis athletes.Methods:There are 40 subjects took part in the study, including 25 male table tennis athletes of the second national team, which was divided into normal group (NA)with 13 athletes and imbalance group(IA)with 12 athletes, and 15 healthy young men as control group (CON)whose age, body height and weight were matched with athletes. The IA group was randomly divided into no-rehabilitation group(NIA)and rehabilitation group (RIA),with 6 athletes respectively.The instrumentations includes the VICON motion analysis system with 6 infrared cameras and the NORAXON assemblies with 8-channel. The muscles selected to be measured include 3 parts of trapezius, serratus anterior, pectoralis major, anterior and posterior deltoid as well as infraspinitus. The static and dynamic data (i.e. strike with obverse and reverse side)of kinematics and synchronic SEMG data were measured. After the measurement reliability was tested, all subjects were evaluated by first clinical examination and synchronic measurements, and all athletes of IA group performed previous measurements after 8-week rehabilitation.The clinical parameters included lateral scapular slide(LSS)measurement, diagnosis, and the disabilities of the arm. shoulder and hand score(DASH)and its sports module. The kinematics parameters included shoulder functional joint center(FJC), peak acceleration of distal humeral during strike. The SEMG parameters included each muscle peak activity during the different movement types expressed as a percentage of maximal voluntary contraction(MVC%), peak muscle activity time (PAMT)during strikes, and normalized SEMG signal ratios of UT/SA and MT/PM. Single-sample t-test and one-way ANOVA were used for statistics analysis.Results:For LSS, there is no significant different between CON and NA group, while significant lower than IA group, after rehabilitation, RIA group significant lower than before in position A, B, and C(P=0.001,P=0.006, and P=0.001 respectively). For DASH score and its sports module, there is no significant different between CON and NA group, while significant lower than IA group, after rehabilitation, RIA group significant lower than before(P=0.012), but higher than NA group(P<0.001).For diagnosis, after rehabilitation, anterior SAIS was decreased, and fasciitis of shoulder was disappeared.For measurement reliability, the intraclass correlation coefficient(ICC) of kinematics and SEMG was range from 0.75 to 0.92, which indicated that the reliability was good. For FJC, there were no significant different between CON and NA group on displacement in any orientations, while IA group had significant lateral, downward, and anterior displacement(P＜0.001). After rehabilitation, RIA group had significant medial, upward, and posterior displacement than before(P＜0.001).For peak acceleration of distal humeral and motion cycle during strikes, the CON group was significant lower than NA and IA group(P<0.05),there is no different before and after rehabilitation in NIA and RIA group.For MVC% during obverse strikes, IA group was higher than CON and NA group(P=0.002), and after rehabilitation, RIA group was lower than NIA group(P< 0.001) in upper trapezius; to middle trapezius, IA group was lower than CON and NA group(P＜0.001), and after rehabilitation, RIA group was higher than NIA group (P< 0.001),but lower than NA group(P=0.002); to serratus anterior, IA group was higher than CON(P=0.042) and NA group(P<0.001), and RIA group was lower than NIA group (P<0.001)after rehabilitation; to anterior deltoid, NA group was lower than CON and IA group(P=0.017), and there were no significant different between RIA and NIA group after training(P=0.068). There were no significant different in other muscles.For MVC% during reverse strikes, IA group was higher than CON and NA group(P< 0.001), and after rehabilitation, RIA group was lower than NIA group(P=0.001) in upper trapezius; to middle trapezius, IA group was lower than CON and NA group(P=0.015), and after rehabilitation, RIA group was higher than NIA group (P=0.003); to serratus anterior, IA group was higher than CON(P=0.004) and NA group(P＜0.001), and RIA group was lower than NIA group (P＜0.001)after rehabilitation. There were no significant different in other muscles.For normalized EMG ratios, NA group was higher than IA group(P<0.001), while after rehabilitation higher than before in RIA group(P<0.001)on UT/SA during strikes; to MT/PM during strikes, NA group was lower than IA group(P＜0.001), while after rehabilitation lower than before in RIA group(P<0.001).For PAMT, there were no significant different among all groups as well as before and after rehabilitation of RIA group. Conclusions:(1) the SMI and SAIS existed in table tennis athletes with shoulder pain. (2) Compared with healthy athletes and common men, the humeroscapular joint of athletes with SMI had anterior, downward, and lateral displacement; during obverse strikes, the athletes with SMI had higher activity in upper trapezius, serratus anterior, and anterior deltoid, and lower middle trapezius activity compared with healthy athletes; during reverse strikes, compared with normal athletes, the athletes with SMI had higher activity in upper trapezius, and serratus anterior, and lower middle trapezius activity. (3) SMI was one of reasons that cause the SAIS of table tennis athletes. The displacement of humeroscapular joint result in lower subacromial space, induced the potential impingement between humeral and anterior-inferior part of acromial during obverse strikes, and posterior-inferior part of acromial during reverse strikes, (4) The rehabilitation protocol on scapular muscle balance is effective to table tennis athletes with SMI, and may release the clinical symptoms. So it should be arranged in athletes'routine training plans. (5) The indexes used to evaluate the scapular muscle balance of table tennis athletes should contain with LSS measurement, DASH score, shoulder FJC, dynamic SEMG of trapezius and serratus anterior, and the ratios of UT/SA and MT/PM.