This quasi-experimental study was approved by the institutional review board of the Korea Institute of Sport Science. To evaluate the short-term effectiveness of SFT on scapular movement during the flat serve among tennis players with and without shoulder pain, SFT was applied to their torso aligned with the lower trapezius. The scapular position in five events, angular velocity, and moment of scapular movement in four phases during the serve were analyzed. Experiments were conducted in an indoor tennis court for three-dimensional analysis, and all participants performed a warm-up of at least 15 minutes with their own racquet to prevent injury and adapt to the experimental environment. All tests were carried out on the same day.
A total of 13 professional tennis players took part in the study, including 7 players who had no dysfunction during full arm elevation and/or history of shoulder pain (NSP) in the 6-month period preceding this study (age: 21.29 ± 1.38 yrs; height: 172.42 ± 9.13 cm; weight: 68.86 ± 7.34 kg; years playing tennis : 12.00 ± 2.38 yrs), and 6 players with shoulder pain (SP) with at least three positive results for Hawkins-Kennedy test, Neer test, empty can test, and painful arc test (age: 21.83 ± 0.75 yrs; height: 173.33 ± 16.04 cm; weight: 68.00 ± 12.50 kg; years playing tennis: 10.83 ± 1.94 yrs). There were no significant differences in demographic data between the two groups, and all participants signed a statement of informed consent prior to participation in the study.
Kinematic data were collected in an indoor tennis court using the Qualisys motion capture system (Qualisys AB, Sweden) consisting of 10 infrared cameras (7+, Qualisys AB) and a 1-color video camera (Oqus 2c, Qualisys AB). The marker set included 11 markers (diameter of 14 mm), located to the spinous processes of the 7th cervical and 8th thoracic vertebrae, suprasternal notch, xiphoid process, acromioclavicular joint, middle of scapular spine, root of the scapular spine, inferior angle of scapula, acromial angle of the scapula, glenohumeral rotation center, and elbow medial and lateral epicondyles of the participants’ dominant arm according to the International Society of Biomechanics recommendations (27). An additional acromion marker cluster was attached to the meeting point between the acromion and scapula spine, and the reflective markers were attached to the participants’ own racquet and tennis ball to register the impact event. The specific static model calibration for each participant defined the scapulothoracic joint motion axes and planes.
Before the measurement of scapular movement, all participants performed the 15-minute warm-up and were educated to perform 12 flat serves to land the ball in the service box at their greatest velocity (28). Subsequently, SFT was applied to the participants’ torso aligned with the lower trapezius by a well-trained expert, and the procedures were repeated and measured in the same way.
The scapular data of three successful serves were collected and analyzed. The tennis serve was divided into four phases based on five key events (28): (E1) ball release, (E2) first 75% of the cocking phase, (E3) maximal external rotation of the humerothoracic joint, (E4) ball impact, and (E5) minimal height of the tennis racquet. The cocking phase was defined as the motion from ball release to maximal external rotation of the humerothoracic joint (28). The scapular posterior/anterior tilt, upward/downward rotation, and internal/external rotation relative to the thorax were measured at each event, and the angular velocity and joint moment were calculated for each phase.
Scapular Focused Taping
The SFT technique was applied to the scapula of the participants’ dominant arm using two pieces of standard 2-inch tape (MSSM Kino Soft Inc, Seoul, South Korea) according to the method suggested by Lewis et al. (29). First, the participants were seated on a stool while keeping their backs straight and asked to fully retract and depress their scapula. One I-shaped tape was applied from the 1st to the 12th thoracic vertebra with light tension (15-25%) and the other I-shaped tape was applied diagonally from the middle of the scapular spine to the 12th thoracic vertebra with the same tension. Subjects were not required to actively maintain this posture after tape application (30).
Statistical analysis was performed with SPSS 23.0. (IBM Corporation, New York, USA) with significance levels set at 5%. The differences between the groups for continuous data were compared using an independent t-test at each event and phase. A dependent t-test was used to compare the data depending on the application of SFT, and 2-way ANOVA with repeated measures was used to identify interactive effects between groups and taping condition.