Background: Various functional tests such as upper quarter Y-balance test (UQYBT) are used to evaluate shoulder stability and mobility in clinical or sports fields. Previous studies have been conducted to determine the correlation between the scapular or trunk muscle and UQYBT. However, the correlation between UQYBT and hip flexor, which can be considered as a core muscle, has not been confirmed.
Objects: To verify the relationship between the UQYBT and scapular muscle (scapular pro-tractor and lower trapezius [LT]), trunk muscle, and hip flexor strengths in healthy male par-ticipants.
Methods: A total of 37 healthy male participants were recruited and underwent UQYBT in the push-up posture. The isometric strength of the scapular protractor, LT, trunk flexor and ex-tensor, and hip flexors were measured using a smart KEMA strength sensor (KOREATECH Inc.).
Conclusion: This study showed that the strength of the scapular muscles, trunk muscles, and hip flexor muscles correlated to the UQYBT. Therefore, the strength of not only the scapular and trunk muscles but also the hip flexor muscles should be considered to improve the UQYBT.