Abstract
Objective
The purpose of this study was to evaluate the influence of a posture-cuing shirt on internal rotation velocity of the shoulder during a tennis swing and to determine this influence on shoulder external rotation position.
Methods
Nine healthy competitive college tennis players from a Division III college participated in this study. High-speed motion capture allowed for 3-dimensional analysis of shoulder kinematics during a tennis serve. Two conditions were evaluated while the athletes performed a high-velocity tennis serve: a standard tennis shirt and a posture-cuing shirt.
Results
Shoulder internal rotation velocity increased when wearing the posture-cuing shirt. Peak internal rotation velocity increased from 960.61°/s ± 93.24°/s to 1217.96°/s ± 155.01°/s (t = –1.76, P = .058). Internal rotation velocity at the time of impact increased from 765.18°/s ± 95.48°/s to 900.54°/s ± 105.33°/s (t = –1.50, P = .086). Shoulder maximum external rotation did not differ between the 2 conditions, at 172.00° ± 2.92° and 170.89° ± 3.70° (t = 0.325, P = .754).
Conclusions
Wearing a posture-cuing shirt may possibly alter shoulder kinematics during an overhead sport activity such as tennis. Internal rotation velocity seemed to improve while wearing this shirt, although shoulder external rotation position did not change. It is not known if these improvements can influence injury risk.
Key Indexing Terms: Shoulder; Posture; Kinesiology, Applied; Biomechanical Phenomena
Introduction
The anatomy of the shoulder joint presents unique problems for overhead athletes, such as tennis players, baseball pitchers, and volleyball players. The effective and efficient function of the shoulder complex requires the coordinated movements of the scapula, clavicle, and glenohumeral joint.1 Instability of the glenohumeral joint, altered kinematics of scapular motion, and muscle imbalances of the shoulder complex place overhead athletes at increased risk for shoulder injury.2, 3, 4, 5 These functions have been associated with injury risk and dysfunction specific to the glenohumeral joint, which is dependent on proper scapular motion during upper extremity activities.5, 6, 7
With tennis in particular, the tennis serve is considered the most important stroke in this sport and is also considered the most influential on injury occurrence to the shoulder in tennis players.8, 9 The tennis serve involves the coordinated effort of the lower extremities and trunk and also the integrated motions of the scapula with the humerus.9 Not surprisingly, shoulder internal and external rotation motions, which are dependent on scapular positioning, are associated with shoulder injury in athletes, including tennis players.9, 10 For instance, glenohumeral internal rotation deficit, which is defined as the imbalance of shoulder arc of rotation, creating excessive external rotation and a lack of internal rotation range of motion (ROM), is associated with scapular dyskinesia and subsequent injury to the shoulder of overhead athletes.3, 10, 11, 12 As noted in prior studies, shoulder internal rotation is directly associated with racquet speed and ball velocity after impact, and shoulder external rotation is associated with shoulder internal rotation function.8, 9, 10 Hence, effective movement of the glenohumeral joint, during the tennis serve, is a critical element to the mechanics of the serve but also critical to minimizing the risk of injury to the shoulder.
A recent adjunct to shoulder prevention and rehabilitation programs is the addition of kinesiotape (KT). Kinesiotaping has been reported to increase both muscle activation and ROM when used in conjunction with training programs.13 It has also been reported to improve the resting position of the scapula.14 Along with improving the starting position of the scapula, Shaheen et al15 reported that taping increased ROM of scapular retraction, upward rotation, and posterior tilting in asymptomatic patients. Finally, taping has also been reported to increase serratus activation during entire range of scaption (shoulder abduction in the plane of the scapula), as well as facilitate the activation of the lower trapezius.16 Because normal scapular positioning and ROM have been proven to be important in injury prevention, taping may be a great supplemental treatment for athletes.13, 14, 17
A unique garment recently introduced to the athletic community is a posture-cuing (PC) shirt that attempts to replicate the influence of KT on upper body posture, including scapular positioning. This shirt is designed to reproduce the KT influence of the shoulder girdle, particularly the scapula. The shirt is also compressive, which is linked to overall improved recovery.18, 19 Limited research exists as to the effectiveness of these PC shirts on shoulder function. Cole et al20 reported that these types of shirts with tension have improved the postural alignment of the shoulder, decreased forward shoulder posture, and increased activation of the lower trapezius during scaption and flexion in overhead athletes with forward-head, rounded-shoulder posture. Russell et al21 also reported that the PC shirt improved function for pitchers. These studies support the need for more research on such technology, specifically in populations at risk for upper extremity injuries.
The purpose of this study was to determine any influence of a compressive PC shirt on the kinematics of the glenohumeral joint during a tennis serve. This preliminary study attempted to determine whether a PC shirt has any impact on joint kinematics (ie, joint positioning and joint motion) during an overhead tennis serve, given that prior research on KT and PC shirts indicated influence on scapular positioning. It was hypothesized that the PC shirt, reported to influence the scapula and upper torso, would provide a change in joint kinematics of the glenohumeral joint during an overhead tennis serve. We focused on internal rotation velocity, which is associated with ball velocity of a serve, and shoulder external rotation position, which is associated with glenohumeral internal rotation deficit and shoulder function.10
Methods
Participants
Participants were recruited from a Division III university tennis program. Participants included 4 men (Xage = 19.5 ± 1.3 years; Xht = 1.78 ± 0.05 m) and 5 women (Xage = 20.0 ± 0.71 years; Xht = 1.66 ± 0.04 m), and all had a minimum of 3 years of competitive tennis experience. Participants were healthy with no recent history of upper extremity injuries in the past 6 months. This study was granted exemption status by the university’s Institutional Review Board.
Procedures
All participants completed a standard warmup as prescribed by the tennis program. The participants then completed 2 full serves at game speed effort. One serve (control) was performed while wearing the standard athletic clothing for the participant. A second serve was performed while wearing the PC shirt. Order of the conditions was not randomized; all participants performed the control condition first and the PC shirt condition second. Participants were not blinded to the 2 conditions.
Data were collected using a 3-dimensional (3-D) motion analysis system. This system included 2 high-speed cameras at a rate of 240 Hz (EXZR200 cameras, Casio Computers Ltd), positioned approximately orthogonal to the athlete, with 1 camera parallel to the serve line and the second camera positioned at approximately 90°, from an anterior view of the participant. Before collecting movement data, the capture field was calibrated using an 8-point direct linear transformation object placed in the serve area. The optical data were then digitized using Motus software (Vicon Motus, Version 10.0; Vicon, Englewood, NY), identifying joint centers for the shoulder, elbow, wrist, hand, and torso, as well as identifying markers in the center of the tennis handgrip and the head of the racquet. The 2-D data were first smoothed with fast Fourier transformation using a 28-ms window. In addition, the elbow (6 Hz) and wrist (14 Hz) were filtered using a Butterworth low-pass filter. The filtered 2-D data were then incorporated into a vector system to produce 3-D coordinates, using a Butterworth filter at 13 Hz. Anatomic references were then created using these 3-D filtered coordinates to produce a linkage system to calculate the kinematic data. All kinematic data were calculated using the Zenolink software program (ZenoLink, Endicott, NY). The variables of interest focused on joint angular positions and angular velocities of the glenohumeral joint. Specifically, peak internal rotation velocity, peak external rotation position, and internal rotation velocity at the time of impact with the tennis ball were all estimated.
Data Analysis
Kinematic data of shoulder positions (peak shoulder external rotation, peak internal rotation velocity, internal rotation velocity at impact) were averaged across the participants. Paired t tests were used to determine if differences existed between the control condition and the PC shirt condition. Because this was an exploratory study, a P value of .10 was established a priori to identify potentially clinically relevant trends.
Results
Shoulder internal rotation velocity increased when wearing the PC shirt. Peak internal rotation velocity increased from 960.61°/s (standard error [SE] = 93.24) to 1217.96°/s (SE = 155.01; t = –1.76, P = .058). Internal rotation velocity at the time of impact increased from 765.18°/s (SE = 95.48) to 900.54°/s (SE = 105.33; t = –1.50, P = .086). Shoulder maximum external rotation did not differ between the 2 conditions at 172.00° (SE = 2.92) and 170.89° (SE = 3.70; t = 0.325, P = .754).
Discussion
The results indicated there was a significant increase in both peak internal rotation velocity and internal rotation velocity at the time of impact while wearing the PC shirts. There were no significant changes in maximum shoulder external rotation. In terms of improved performance, we can only speculate that the improved shoulder internal rotation velocity might result in improved ball velocity after contact with the racquet; we did not measure ball velocity in this study. However, prior research by Sprigings et al10 reported that racquet-head speed was most dependent on shoulder internal rotation velocity. The present results are fairly consistent with prior research in terms of peak internal rotation velocity, with values ranging from 620°/s in trained tennis players to 1370°/s in professional female tennis players.22, 23 However, the magnitude of external rotation position in our study exceeds that of other researchers (115-140°).22
The changes in internal rotation speed may be attributed to changes in scapular positioning while wearing the PC shirts given the reported influence of a PC shirt on scapular and torso posture, as well as the influence of kinesiotaping on scapular motion.1, 14, 16, 20 However, this is only conjecture because we did not study the scapular motion and base this assumption on prior research. Ujino et al14 hypothesized that “KT (kinesiotape) may have placed the scapula more posterior which may increase activation of shoulder musculature.”14, 16 Posture-cuing shirts were reported to provide similar influence, as noted by Cole et al.20 They observed that “tension straps on PC shirts decrease forward shoulder angle and alters some muscle activity,” resulting in a decrease in upper trapezius and an increase in lower trapezius muscle activity during shoulder flexion while wearing a PC shirt. These improvements in scapular motion, either with KT or PC, are attributed to improved function of the glenohumeral joint during overhead motions.14, 16, 20 We observed improved speed of the glenohumeral joint while the athletes wore the PC shirt, yet we did not observe any changes in glenohumeral external rotation. If the PC shirt did in fact influence scapular positioning, we suspect this would improve internal rotation speed, but we also would suspect a change in shoulder external rotation, which we did not observe. Because we did not evaluate scapular position in our particular study, any explanation for the improvement in glenohumeral internal rotation speed is speculative.
The PC shirts may also increase the tactile input, influencing the time to activate the muscles of the scapula stabilizers to maintain a stable base for the humeral internal rotators to function. Kinesiotape has been reported to “provide additional sensory feedback...pressure and stretching effect of KT stimulates cutaneous mechanoreceptors which conveys information about joint position and movement therefore enhancing proprioception.”13 Cole et al20 also hypothesized that PC shirts would have the same effect as KT, “slight EMG changes in both conditions (compression shirts with or without tension straps) might suggest an effect on joint alignment due to enhanced proprioception and proprioceptive feedback.”20 We can only postulate that the PC shirt might have influenced muscle activation, which may have contributed to the changes in internal rotation velocity of the shoulder. However, just as with scapular positioning, we did not assess muscle activity in this current study and thus this relationship is speculative.
Limitations
Some limitations to this study are the small number of participants because of the specific inclusion criteria. Participants only completed 1 serve in each condition, leading to possible error; more trials would decrease the amount of error and increase the validity and reliability of the results. The motion capture system employed in this study has proven reliability in previous dynamic studies; however, we did not directly measure the error in this study.23 The participants were also not randomized as to which condition they performed first; all participants performed first with normal clothing, then with the PC shirt. The lack of randomization could have led to an order effect or even a placebo effect as a result of the athletes’ expectations of the PC shirts. Also, starting scapular position was not measured, so the cause for the change in velocity can only be theorized. Future research should address long-term effects of PC shirts. A longitudinal study should address strength, starting alignment, and ROM. Long-term changes in any of these categories can give us a better insight into functional changes like velocity while wearing PC shirts. In addition, it will be important to study the influence of PC shirts on scapular kinematics in order to better appreciate any possible relationship between glenohumeral motion and scapular motion while wearing a PC shirt. Finally, given the demonstrated influences of KT on scapular and shoulder kinematics, a comparison study between PC and KT on overhead kinematic activities such as the tennis serve is highly warranted.
Conclusions
This study provides preliminary findings that suggest a PC shirt might provide influence on glenohumeral joint motion during overhead activities such as a tennis serve. Specifically, a change in relative internal rotation velocity of the shoulder was observed when athletes wore a PC shirt. Whether this is a result of a change in glenohumeral joint positioning, scapular motion, or muscle activation is a subject for future research.
Funding Sources and Conflicts of Interest
No funding sources or conflicts of interest were reported for this study.
Contributorship Information
Concept development (provided idea for the research): D.J.C., J.Z., C.O., E.B., H.F., D.S.
Design (planned the methods to generate the results): D.J.C., J.Z., C.O., E.B., H.F., D.S.
Supervision (provided oversight, responsible for organization and implementation, writing of the manuscript): D.J.C., J.Z., C.O., E.B., H.F., D.S.
Data collection/processing (responsible for experiments, patient management, organization, or reporting data): D.J.C., J.Z., C.O., E.B., H.F., D.S.
Analysis/interpretation (responsible for statistical analysis, evaluation, and presentation of the results): D.J.C., J.Z., C.O., E.B., H.F., D.S.
Literature search (performed the literature search): D.J.C., J.Z., C.O., E.B., H.F., D.S.
Writing (responsible for writing a substantive part of the manuscript): D.J.C., J.Z., C.O., E.B., H.F., D.S.
Critical review (revised manuscript for intellectual content, this does not relate to spelling and grammar checking): D.J.C., J.Z., C.O., E.B., H.F., D.S.
Practical Applications
-
•
Compression shirts and PC shirts may possibly improve athlete performance.
-
•
A PC shirt may improve athlete upper body function, particularly for overhead activities.
-
•
Coaches might consider recommending PC shirts as part of training for athletes, however more research is necessary.
Alt-text: Image 1
References
- 1.Neumann D. 2nd ed. 2010. Kinesiology of the Musculoskeletal System Foundations for Rehabilitation. St. Louis, MO. [Google Scholar]
- 2.Alexander M. Overhead throwing mechanics and injuries. Clin Rev Phys Rehabil Med. 1994;6(3):291–315. [Google Scholar]
- 3.Borich M., Bright J., Lorello D., Cierminski C., Buisman T., Ludewig P. Scapular angular positioning at end range internal rotation in cases of glenohumeral internal rotation deficit. J Orthop Sports Phys Ther. 2006;36(12):926–934. doi: 10.2519/jospt.2006.2241. [DOI] [PubMed] [Google Scholar]
- 4.Wang C., McClure P., Pratt N., Nobilini R. Stretching and strengthening exercises: their effect on three-dimensional scapular kinematics. Arch Phys Med Rehabil. 1990;80(8):923–929. doi: 10.1016/s0003-9993(99)90084-9. [DOI] [PubMed] [Google Scholar]
- 5.Van der Hoeven H., Kibler W. Shoulder injuries in tennis players. Br J Sports Med. 2006;40(5):435–440. doi: 10.1136/bjsm.2005.023218. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6.Edmonds E., Dengerink D. Common conditions in the overhead athlete. Am Fam Physician. 2014;89(7):537–541. [PubMed] [Google Scholar]
- 7.Kibler W., Ludewig P., McClure P., Michener L., Bak K., Sciascia A. Clinical implications of scapular dyskinesis in shoulder injury: the 2013 consensus statement from the ‘scapular summit’. Br J Sports Med. 2013;47(14):877–885. doi: 10.1136/bjsports-2013-092425. [DOI] [PubMed] [Google Scholar]
- 8.Reid M., Elilott B., Alderson J. Shoulder joint loading in the high performance flat and kick tennis serves. Br J Sports Med. 2007;41(12):884–889. doi: 10.1136/bjsm.2007.036657. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 9.Whiteside D., Elliott B., Lay B., Reid M. The effect of age on discrete kinematics of the elite female tennis serve. J Appl Biomech. 2013;29(5):573–582. doi: 10.1123/jab.29.5.573. [DOI] [PubMed] [Google Scholar]
- 10.Sprigings E., Marshall R., Elliott B., Jennings L. A three-dimensional kinematic method for determining the effectiveness of arm segment rotations in producing racquet-head speed. J Biomech. 1994;27(3):245–254. doi: 10.1016/0021-9290(94)90001-9. [DOI] [PubMed] [Google Scholar]
- 11.Struyf F., Nijs J., De Graeve J., Mottram S., Meesusen R. Scapular positioning in overhead athletes with and without shoulder pain: a case-control study. Scand J Med Sci Sports. 2011;21(6):809–818. doi: 10.1111/j.1600-0838.2010.01115.x. [DOI] [PubMed] [Google Scholar]
- 12.Stickley C., Hetzler R., Freemyer B., Kimura I. Isokinetic peak torque ratios and shoulder injury history in adolescent female volleyball athletes. J Athl Train. 2008;43(6):571–577. doi: 10.4085/1062-6050-43.6.571. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 13.Williams S., Whatman C., Hume P., Sheerin K. Kinesio taping in treatment and prevention of sports injuries a meta-analysis of the evidence for its effectiveness. Sports Med. 2012;42(2):153–164. doi: 10.2165/11594960-000000000-00000. [DOI] [PubMed] [Google Scholar]
- 14.Ujino A., Eberman L., Kahanov L., Renner C., Demchak T. The effects of kinesio tape and stretching on shoulder rom. Int J Athl Ther Train. 2013;18(2):24–28. [Google Scholar]
- 15.Shaheen A., Villa C., Lee Y., Bull A., Alexander C. Scapular taping alters kinematics in asymptomatic participants. J Electromyogr Kinesiol. 2013;23(2):326–333. doi: 10.1016/j.jelekin.2012.11.005. [DOI] [PubMed] [Google Scholar]
- 16.Hsu Y., Chen W., Wang W., Shih Y. The effects of taping on scapular kinematics and muscle performance in baseball players with shoulder impingement syndrome. J Electromyogr Kinesiol. 2009;19(6):1092–1099. doi: 10.1016/j.jelekin.2008.11.003. [DOI] [PubMed] [Google Scholar]
- 17.Thelen M., Dauber J., Stoneman P. The clinical efficacy of kinesio tape for shoulder pain: a randomized double-blind, clinical trial. J Orthop Sports Phys. 2008;38(7):389–395. doi: 10.2519/jospt.2008.2791. [DOI] [PubMed] [Google Scholar]
- 18.Tsuruke M., Ellenbecker T. Effects of compression garment on shoulder external rotation force outputs during isotonic contractions. J Strength Cond Res. 2013;27(2):519–525. doi: 10.1519/JSC.0b013e3182578145. [DOI] [PubMed] [Google Scholar]
- 19.Pearce A., Kidgell D., Grikepelis L., Carlson J. Wearing a sports compression garment on the performance of visuomotor tracking following eccentric exercise: a pilot study. J Sci Med Sport. 2008;12:500–502. doi: 10.1016/j.jsams.2008.06.002. [DOI] [PubMed] [Google Scholar]
- 20.Cole A., McGrath M., Harrington S., Padua D., Rucinski T., Prentice W. Scapular bracing and alteration of posture and muscle activity in overhead athletes with poor posture. J Athl Train. 2013;48(1):12–24. doi: 10.4085/1062-6050-48.1.13. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 21.Russell E., Andrews J.R., Menon S., Novakovich P., Witte K. Compression shirts decrease pain and improve performance in youth pitchers. Med Sci Sports Exerc. 2013;45(5):S426. [Google Scholar]
- 22.Fleisig G., Nicholls R., Elliott B., Escamilla R. Kinematics used by world class tennis players to produce high-velocity serves. Sports Biomech. 2003;2(1):51–64. doi: 10.1080/14763140308522807. [DOI] [PubMed] [Google Scholar]
- 23.Meldrum D., Shouldice C., Conroy R. Test-retest reliability of three dimensional gait analysis: including a novel approach to visualizing agreement of gait cycle waveforms with Bland and Altman Plots. Gait Posture. 2014;39(1):265–271. doi: 10.1016/j.gaitpost.2013.07.130. [DOI] [PubMed] [Google Scholar]