# Shoulder Rotational and Dynamic Stability Profiles in Elite and National-Level Tennis Players: A Pilot Study Using an Electromechanical Dynamometer for Measuring Isometric Strength

## TL;DR

This study compares shoulder strength and stability in elite and national-level tennis players to identify differences that could affect performance and injury risk.

## Contribution

The study introduces a pilot approach using an electromechanical dynamometer to assess shoulder profiles in tennis players.

## Key findings

- Elite male players showed significant shoulder asymmetries due to higher training volumes.
- Dynamic stability scores were consistently low with side-to-side differences in most players.
- National-level female players had lower internal rotation strength and ER/IR ratio asymmetry.

## Abstract

Background/objective: Tennis involves repetitive overhead movements, and understanding the relationship between shoulder mobility, dynamic stability, and isometric strength could be crucial for developing targeted training programmes to enhance performance and reduce injury risk. This study aimed to assess shoulder rotational mobility, dynamic stability, and isometric strength profiles in elite and national-level tennis players. Methods: Twenty-four male and female athletes were grouped by competitive level: National-Level Female Group (NFG); National-Level Male Group (NMG); and Elite Male Group (EMG). Shoulder isometric strength was evaluated using an electromechanical dynamometer (Dynasystem), while rotational mobility and dynamic stability were assessed using standardised protocols. Results: Significant anthropometric differences in height, weight, and leg length were identified between NFG and the other groups (p < 0.001). NMG showed reduced external rotation compared to NFG and EMG in the dominant shoulder (p < 0.05). EMG exhibited significant asymmetries in external rotation between the dominant and non-dominant shoulders, which may be attributed to higher training volumes (p < 0.05; ES = 0.994). No significant differences were found in isometric strength across the groups, although NFG showed lower internal rotation strength and ER/IR ratio asymmetry between the dominant and non-dominant shoulder (p < 0.05). Dynamic stability scores were consistently low, with asymmetries between the dominant and non-dominant sides in most cases. Conclusions: These findings suggest the need for targeted training to address asymmetries and enhance dynamic stability. Caution is advised when generalising these results due to the limited sample size. Future research should include more participants and explore associations with performance metrics, such as serve speed and playing style.