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Assessing Shoulder Strength and Range of Motion in Normal and Symptomatic Swimmers

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Date

2024

Authors

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Brughelli , Matt

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Thesis

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Master of Health Science

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Auckland University of Technology

Abstract

Swimming is a recreational and competitive sport that can be identified by its repetitive and coordinated movements between various parts of the body. Unlike other sports where the lower body initiates and contributes to the propulsive forces, this is the primary role of the upper body. Although the cause of shoulder pain in swimmers is believed to be multifactorial, some modifiable factors such as muscle strength imbalance, altered muscle endurance and coordination, and deficits in the shoulder joint mobility, can predispose swimmers to shoulder pain or injury. Chapter 2 of this thesis includes a literature review on shoulder strength and range of motion in swimmers with and without pain. The literature review highlighted the limited research using isokinetic dynamometry to assess shoulder concentric and eccentric strength in swimmers who experience pain. Also, most of the studies analyzed these strength measures using absolute strength values and the conventional concentric and eccentric (ER:IR) ratios. Literature examining shoulder strength in other overhead sports has found that using a functional ratio of eccentric versus concentric (eccER:conIR) to be more appropriate. This literature review also showed that shoulder ROM of swimmers has primarily been assessed in supine or standing. On the basis of the findings of this literature review, this thesis sought to examine the differences in shoulder rotational strength in swimmers who have pain or not using the Humac Norm isokinetic dynamometer. For additional analysis on the differences between the painful and non-painful side, the researcher aimed to use the functional ratio (eccER:conIR) which has previously been studied twice in this population. Additionally, this thesis intended to measure the shoulder internal and external rotation ROM of swimmers using an inclinometer in prone. This position was selected as it is specific to swimming. Three out of the four strokes are performed in prone. Since the cross-sectional study included in this thesis is the first to use the Humac Norm isokinetic dynamometer and the inclinometer in prone to assess the shoulder of swimmers, in particularly those with shoulder pain, this thesis also aimed to determine the inter- and intra-session reliability of these objective measures. The reliability study (chapter 3) found moderate to excellent inter-session reliability (ICC: 0.68-0.98; CV: 4.80-19.70; SEM: 1.71-5.36) and excellent intra-session reliability (ICC: 0.98-1.00; CV: 1.50-19.80; SEM: 0.00-1.84) for the use of an inclinometer in prone for swimmers with and without shoulder pain. Moderate to excellent inter-session reliability was found for the use of the Humac Norm isokinetic dynamometer to assess a swimmer’s shoulder strength (ICC: 0.60-1.00; CV: 6.80-60.50; SEM: 0.00-7.20). The Humac Norm isokinetic dynamometer showed excellent intra-session reliability (ICC: 0.99-1.00; CV: 2.20-8.20; SEM: 0.00-1.31). Although the Humac Norm isokinetic dynamometer showed moderate to excellent intersession relative reliability, the high CV and SEM values indicated less adequate absolute reliability. Whereas the intra-session absolute reliability, during the second session, was more adequate. This shows the importance of having at least one familiarization session, particularly for the eccentric testing protocol. Eccentric movement is unique and not performed on a daily basis hence the importance for participants to practice this movement to ensure testing proficiency. Future research using the Humac Norm isokinetic dynamometer to assess swimmers’ shoulders should include at least one familiarization session. Chapter 4 included a cross-sectional study design to investigate strength hand ROM in swimmers with and without pain. The strength data indicated no significant side to side difference in shoulder external or internal rotation strength in asymptomatic swimmers; however, the external rotators were significantly stronger when working eccentrically than concentrically (R: p= 0.01, ES= -1.76; L: p=0.01, ES= -2.17). There was also no significant difference in functional eccER:conIR ratio between the left and right side (p=0.66). On the contrary, swimmers with shoulder pain were significantly weaker on their symptomatic side during concentric internal rotation (p=0.05, ES=-0.96). Additionally, swimmers who have painful shoulders had a significantly greater functional ratio on the symptomatic side (p=0.04). Lastly, there was no significant difference in internal and external rotation ROM regardless of pain being present or not. Further research is required to validate the findings of our study as it is the second study to use the functional ratio to evaluate the differences in shoulder strength in swimmers with shoulder pain. Also, it is the first study to assess shoulder ROM using an inclinometer in prone. On the basis of the findings in this thesis, practical implications include that health professionals or strength coaches working with swimmers should measure shoulder ROM in prone as they may get a more practical and reliable assessment of the shoulder’s mobility. Lasty, health professionals involved in the management of shoulder injuries in swimmers should consider using the functional ratio (eccER:conIR) to evaluate the muscle balance around the shoulder joint as it is more appropriate and sport-specific, especially considering how the internal and external rotators interact during the propulsive phase in swimming.

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http://hdl.handle.net/10292/17874

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