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Galea J1, Xerri de Caro J1
1University of Malta, Msida, Malta
Background: The shoulder is one of the most mobile and flexible joints that requires several mechanisms to keep it stable. The complex structure allowing large degrees of freedom of movement exposes it to many injuries. Water polo is an overhead throwing sport with repetitive and excessive overhead throwing motions often resulting in muscle imbalances between the medial and lateral rotators and may be regarded as prevalent to injuries. Although it is well documented that water polo players suffer from shoulder dysfunction, the prevalence of imbalances in the shoulders of male junior athletes in Malta is not fully understood as very little research has been conducted in this field locally.
Purpose: To investigate muscle strength ratios between the medial and lateral rotators of the shoulder in competitive water polo junior male athletes in Malta with the purpose of understanding their strength patterns.
Methods: A matched case-control study design was followed. Anthropometric data was collected on arm dominance, BMI and engagement in water polo. Data on isometric torque was collected for medial (MR) and lateral rotation (LR) on both shoulders using the Lafayette® dynamometer and adopting a standardised position with the arm fixed in abduction at 20° and the elbow flexed at 90°. Data was analysed statistically for normality and correlation.
Results: 13 junior male water polo athletes (15.5 years ±0.5) and 10 controls (14.4 years ±0.5) met the inclusion criteria. Mean isometric torque ratio for MR:LR in the water polo group dominant shoulder was 1.25 ±0.20 compared to the control group 1.36 ±0.14. These fell within the normal parameters of 1.20 to 1.40 (4:3 for balanced shoulder rotation strength). The mean isometric torque ratio for MR:LR in the water polo group non-dominant shoulder was 1.45 ±0.19 compared to the control group 1.15 ±0.18. These fell outside the normal parameters. Analysis of the correlation between peak torque impulse, MR:LR torque impulse ratio and BMI found a moderate and significant correlation between (i) the peak torque impulse and MR:LR torque impulse ratio (r = 0.518, p 0.001) and (ii) the MR:LR torque impulse ratio and BMI (r = 0.490, p 0.018). The correlation between BMI and peak torque impulse was strong (r = 0.753, p .001).
Conclusion(s): The positive correlation indicates that a greater BMI resulted in greater peak torque impulse values. The findings from this study highlight that the water polo group does not show evidence of any imbalance in the dominant shoulder when compared to a matched control group; unlike the non-dominant shoulder. These findings suggest that in the non-dominant shoulder only, either the medial rotators are excessively stronger or the lateral rotators are excessively weaker.
Implications: The findings highlight little support for an increased risk of injury due to muscle imbalance in the dominant arm in this cohort. There is the potential for injury in the non-dominant shoulder, yet the risk is the same as in the normal population. The study brings to attention the importance of maintaining regular screening and testing of adolescent athletes as prevention of injuries.
Keywords: Shoulder Joint, Overhead throwing, Muscle Imbalances
Funding acknowledgements: None.
Purpose: To investigate muscle strength ratios between the medial and lateral rotators of the shoulder in competitive water polo junior male athletes in Malta with the purpose of understanding their strength patterns.
Methods: A matched case-control study design was followed. Anthropometric data was collected on arm dominance, BMI and engagement in water polo. Data on isometric torque was collected for medial (MR) and lateral rotation (LR) on both shoulders using the Lafayette® dynamometer and adopting a standardised position with the arm fixed in abduction at 20° and the elbow flexed at 90°. Data was analysed statistically for normality and correlation.
Results: 13 junior male water polo athletes (15.5 years ±0.5) and 10 controls (14.4 years ±0.5) met the inclusion criteria. Mean isometric torque ratio for MR:LR in the water polo group dominant shoulder was 1.25 ±0.20 compared to the control group 1.36 ±0.14. These fell within the normal parameters of 1.20 to 1.40 (4:3 for balanced shoulder rotation strength). The mean isometric torque ratio for MR:LR in the water polo group non-dominant shoulder was 1.45 ±0.19 compared to the control group 1.15 ±0.18. These fell outside the normal parameters. Analysis of the correlation between peak torque impulse, MR:LR torque impulse ratio and BMI found a moderate and significant correlation between (i) the peak torque impulse and MR:LR torque impulse ratio (r = 0.518, p 0.001) and (ii) the MR:LR torque impulse ratio and BMI (r = 0.490, p 0.018). The correlation between BMI and peak torque impulse was strong (r = 0.753, p .001).
Conclusion(s): The positive correlation indicates that a greater BMI resulted in greater peak torque impulse values. The findings from this study highlight that the water polo group does not show evidence of any imbalance in the dominant shoulder when compared to a matched control group; unlike the non-dominant shoulder. These findings suggest that in the non-dominant shoulder only, either the medial rotators are excessively stronger or the lateral rotators are excessively weaker.
Implications: The findings highlight little support for an increased risk of injury due to muscle imbalance in the dominant arm in this cohort. There is the potential for injury in the non-dominant shoulder, yet the risk is the same as in the normal population. The study brings to attention the importance of maintaining regular screening and testing of adolescent athletes as prevention of injuries.
Keywords: Shoulder Joint, Overhead throwing, Muscle Imbalances
Funding acknowledgements: None.
Topic: Musculoskeletal: upper limb
Ethics approval required: Yes
Institution: University of Malta
Ethics committee: University and Faculty Research Ethics Committee
Ethics number: 078/2016
All authors, affiliations and abstracts have been published as submitted.
