Original research
Shoulder functional ratio in elite junior tennis players

https://doi.org/10.1016/j.ptsp.2009.11.002Get rights and content

Abstract

Objective

To evaluate shoulder rotation strength and compare the functional ratio between shoulders of elite junior tennis players.

Design

This cross-sectional study evaluated muscular rotation performance of 40 junior tennis players (26 male and 14 female) with an isokinetic dynamometer.

Main outcome measures

Strength variables of external (ER) and internal rotators (IR) in concentric and eccentric modes were considered. For the peak torque functional ratio, the eccentric strength of the ER and the concentric strength of the IR were calculated.

Results

All variables related to IR were significantly higher on the dominant compared to the non-dominant side in males and females (p < 0.05), but only boys exhibited this dominance effect in ER (p < 0.05 and p < 0.001). Regarding functional ratios, they were significantly lower for the dominant shoulder (p < 0.001) and below 1.00 for both groups, indicating that the eccentric strength of the ER was not greater than the concentric strength of the IR.

Conclusion

Elite junior tennis players without shoulder injury have shoulder rotation muscle strength imbalances that alter the normal functional ratio between rotator cuff muscles. Although these differences do not seem to affect the athletic performance, detection and prevention with exercise programs at an early age are recommended.

Introduction

Isokinetic muscular concentric profiles of shoulder movements in tennis have identified sports-specific strength patterns in the dominant arm of tennis players in several previous studies (Chandler et al., 1992, Ellenbecker, 1991, Ellenbecker, 1992, Silva et al., 2006). A significantly greater dominant arm concentric internal rotation strength with no bilateral difference in external rotation strength has been reported in elite, collegiate and adult tennis players (Chandler et al., 1992, Ellenbecker and Roetert, 2003, Ellenbecker, 1991, Ellenbecker, 1992, Gozlan et al., 2006, Kennedy et al., 1993, Ng and Kraemer, 1991). However, these studies provided only strength guidelines, but none of them corresponded to the functionality of the throwing motion.

During throwing, the internal rotator muscles accelerate the upper arm in a concentric action from the position of maximal external rotation to ball impact, before the external rotators eccentrically contract to decelerate this rotation during the follow-through phase of the action (Elliott, 2006). Since the posterior rotator cuff acts to decelerate and stabilize the humerus, eccentric muscular contractions play a role in athletics that is equally significant to concentric muscular contractions (Ellenbecker, Davies, & Rowinski, 1988).

Recent investigations have attempted to establish a functional relationship among the rotator cuff muscles (Niederbracht et al., 2008, Noffal, 2003, Scoville et al., 1997, Yildiz et al., 2006), including a “functional ratio” involving eccentric testing of the shoulder external rotator muscles and concentric testing of the internal rotator muscles (Scoville et al., 1997). Previous studies of overhead sports reported ratios ranging from 1.08 to 1.17 for the dominant shoulder, supporting the argument that eccentric external rotation torque should be greater than concentric internal torque (Ng and Lam, 2002, Noffal, 2003, Scoville et al., 1997, Yildiz et al., 2006). This difference is necessary to overcome and to decelerate not only the strength of the concentrically active internal rotators but also the other segmental forces associated with the dynamic nature of the throwing motion (Noffal, 2003).

To the best of our knowledge, no study has evaluated this functional isokinetic profile of tennis player's strength. This is extremely useful to improve performance, and is also important for prevention and rehabilitation of injuries, especially in younger tennis players. Therefore, our aim was to evaluate the performance of concentric and eccentric muscular rotators and compare the functional ratio between dominant and non-dominant shoulders of elite junior tennis players.

Section snippets

Methods

Forty junior tennis players (26 male, 14 female) with a mean age of 14 years (range, 12–18) were evaluated. For male and female players, mean (SD) weight was 57.9 (15) and 53.9 (9.3) kg, respectively, and mean (SD) height was 168 (14) and 163 (5) cm. To take part in the study, a tennis player had to belong to the Brazilian Tennis Confederation as a junior, be among the 50 best players in his/her category, and have no pathology in the dominant or non-dominant shoulder. All athletes agreed to

Results

Data were significantly different for males and females in all variables studied, with male players showing better performance than female players. In both sexes, all variables related to internal rotation strength in the dominant shoulder were significantly greater than the non-dominant shoulder at both testing speeds (p < 0.05 and p < 0.001) and concentric (Table 1) and eccentric modes (Table 2). Regarding external rotation strength performance, only males exhibited a dominance effect for

Discussion

The main findings of our study were that male junior tennis players had greater external rotation strength in the dominant arm, and both male and female players exhibited a dominance effect in internal rotation strength. Despite these gains, the lower functional ratio in dominant shoulder showed that elite junior tennis players have muscle strength imbalances that could lead to shoulder injuries.

For all measurements of internal rotation strength, the dominant shoulder of male and female tennis

Conclusions

Elite junior tennis players without shoulder injury have shoulder rotation muscle strength imbalances that alter the normal functional ratio between the rotator cuff muscles. These differences in strength do not seem to affect athletic performance, but detection and prevention with exercise programs at an early age are recommended.

Conflict of interest statement

There were no conflicts of interest for the authors of this manuscript.

Funding

No funding was obtained for this study.

Ethical approval statement

All athletes agreed to participate in the study on a voluntary basis, and their legal guardians signed an informed consent approved by the Committee on Ethical Research of the Federal University of São Paulo (CEP n°2042/07).

References (20)

  • G. Gozlan et al.

    Isokinetic dynamometer measurement of shoulder rotational strength in healthy elite athletes (swimming, volley-ball, tennis): comparison between dominant and nondominant shoulder

    Annales de Readaptation et de Medicine Physique

    (2006)
  • J.T. Chandler et al.

    Shoulder strength, power, and endurance in college tennis players

    American Journal of Sports Medicine

    (1992)
  • T. Ellenbecker et al.

    Concentric versus eccentric isokinetic strengthening of the rotator cuff

    American Journal of Sports Medicine

    (1988)
  • T. Ellenbecker et al.

    Age specific isokinetic glenohumeral internal and external rotation strength in elite junior players

    Journal of Science and Medicine in Sport

    (2003)
  • T.S. Ellenbecker

    A total arm strength isokinetic profile of highly skilled tennis players

    Isokinetics and Exercise Science

    (1991)
  • T.S. Ellenbecker

    Shoulder internal and external rotation strength and range of motion of highly skilled tennis players

    Isokinetics and Exercise Science

    (1992)
  • T.S. Ellenbecker et al.

    The application of isokinetics in testing and rehabilitation of the shoulder complex

    Journal of Athletic Training

    (2000)
  • B. Elliott

    Biomechanics and tennis

    British Journal of Sports Medicine

    (2006)
  • J.C. Kennedy et al.

    Concentric and eccentric isokinetic rotador cuff ratios in skilled tennis players

    Isokinetics and Exercise Science

    (1993)
  • G.Y. Ng et al.

    A study of antagonist/agonist isokinetic work ratios of shoulder rotators in men who play badminton

    Journal of Orthopaedic & Sports Physical Therapy

    (2002)
There are more references available in the full text version of this article.

Cited by (55)

  • Preventive approach to shoulder injuries in tennis players

    2023, Journal de Traumatologie du Sport
  • Isokinetic performance of shoulder external and internal rotators in adolescent female handball athletes

    2019, Science and Sports
    Citation Excerpt :

    The bilateral comparison of muscle strength between the upper limbs is often performed because there is a relationship between the limb's asymmetry and a greater risk of injury [32], which in handball athletes may represent 2.5 times more chances of shoulder injury [18]. In the literature, sports that present unilateral upper limb demands often report asymmetries, such as in the study of adolescent volleyball athletes [33,34], tennis [35,36] and baseball [37,38]. Due to the overhead throwing performed extensively by the dominant limb, this limb had been expected to have higher strength values.

  • The isokinetic rotator cuff strength ratios in overhead athletes: Assessment and exercise effect

    2017, Physical Therapy in Sport
    Citation Excerpt :

    Scoville et al. showed only a difference between sides (D > ND) for ECC IR PT/BW (Scoville et al., 1997). All studies except three showed a moderate evidence for a higher CON ER PT/BW at the D side and all but four studies showed higher ECC ER PT/BW at the D side (strength of conclusion 2) (Andrade Mdos et al., 2010; Forthomme et al., 2013; Ng & Lam, 2002; Noffal, 2003; Saccol et al., 2010; Scoville et al., 1997; Wang et al., 2000; Yildiz et al., 2006). When taking into account all the results of the studies comparing D side with ND side, there is moderate evidence for a larger overweight for IR force at de D side compared to ER force for CON and ECC (strength of conclusion 2) (Andrade Mdos et al., 2010; Forthomme et al., 2013; Noffal, 2003; Saccol et al., 2010; Scoville et al., 1997).

View all citing articles on Scopus
View full text