# Muscle Activation Differences Between CKCUEST and Modified CKCUEST: A Pilot Study

## TL;DR

This study compares muscle activation in two upper extremity stability tests and finds the original test activates muscles more strongly.

## Contribution

The study provides new empirical evidence on muscle activation differences between CKCUEST and its modified version.

## Key findings

- CKCUEST showed significantly higher infraspinatus activation compared to modified CKCUEST.
- Anterior deltoid and upper trapezius activation was also higher in CKCUEST for both sides.
- No laterality differences were found in muscle activation during CKCUEST.

## Abstract

Background/Objectives: The validity of shoulder orthopaedic tests to establish a diagnosis has recently been challenged. For this reason, functional tests, such as the Closed Kinetic Chain Upper Extremity Stability Test (CKCUEST), have started to be used in clinical settings. The aim of this study is to compare the electromyography (EMG) activity during the CKCUEST and the modified CKCUEST in a healthy adult population. Methods: Ten male (age: 26.6 ± 4.8) and ten female participants (age: 24.2 ± 6.0) were recruited from a university setting. The Edinburgh Handedness Inventory, the International Physical Activity Questionnaire and the percentage of activation of the maximum voluntary contraction of the infraspinatus, anterior deltoid and upper trapezius, of both upper limbs, throughout the CKCUEST and modified CKCUEST were analysed. Results: The percentage of activation of the infraspinatus (p < 0.01), anterior deltoid (p < 0.01) and upper trapezius (p < 0.01) in both sides was significantly higher in the CKCUEST compared to the modified CKCUEST. No differences were observed between laterality and the activation percentage of the infraspinatus (p > 0.05), anterior deltoid (p > 0.05) and upper trapezius (p > 0.05) in both sides during the CKCUEST. Conclusions: The results of this research showed a higher percentage of EMG activation during the CKCUEST compared to the modified CKCUEST in all the muscular structures analysed, regardless of the participants’ hemibody.