International Journal of Human Movement and Sports Sciences 11(5): 965-973, 2023 http://www.hrpub.org DOI: 10.13189/saj.2023.110504 Impact of Decreased Hamstring Flexibility and Trunk Muscle Strength Performance in Junior Badminton Athletes with a History of Knee Injuries: The Risk of Low Back Pain Tommy Apriantono 1,* , Indria Herman 2 , Bagus Winata 1 , Yun-Dih Chia-Smith 3 , Mochamad Rizky Akbari 1 , Sri Indah Ihsani 1 , Rini Syafriani 1 , Didi Sunadi 1 , Kusnaedi 1 , Samsul Bahri 1 1 Department of Sports Science, School of Pharmacy, Institut Teknologi Bandung, Indonesia 2 Department of Machine Design, Faculty of Mechanical and Aerospace Engineering, Institut Teknologi Bandung, Indonesia 3 Department of Educational Technology, Loyola University Maryland, United States Received March 26, 2023; Revised July 13, 2023; Accepted August 15, 2023 Cite This Paper in the Following Citation Styles (a): [1] Tommy Apriantono, Indria Herman, Bagus Winata, Yun-Dih Chia-Smith, Mochamad Rizky Akbari, Sri Indah Ihsani1, Rini Syafriani, Didi Sunadi, Kusnaedi, Samsul Bahri , "Impact of Decreased Hamstring Flexibility and Trunk Muscle Strength Performance in Junior Badminton Athletes with a History of Knee Injuries: The Risk of Low Back Pain," International Journal of Human Movement and Sports Sciences, Vol. 11, No. 5, pp. 965 - 973, 2023. DOI: 10.13189/saj.2023.110504. (b): Tommy Apriantono, Indria Herman, Bagus Winata, Yun-Dih Chia-Smith, Mochamad Rizky Akbari, Sri Indah Ihsani1, Rini Syafriani, Didi Sunadi, Kusnaedi, Samsul Bahri (2023). Impact of Decreased Hamstring Flexibility and Trunk Muscle Strength Performance in Junior Badminton Athletes with a History of Knee Injuries: The Risk of Low Back Pain. International Journal of Human Movement and Sports Sciences, 11(5), 965 - 973. DOI: 10.13189/saj.2023.110504. Copyright©2023 by authors, all rights reserved. Authors agree that this article remains permanently open access under the terms of the Creative Commons Attribution License 4.0 International License Abstract This study investigated the correlation of hamstring flexibility of athletes affected by knee injuries, with variable trunk muscle strength (TMS) as one of the indicators of low back pain (LBP) in badminton athletes. This cross-sectional study recruited 120 junior badminton athletes, including males and females (n = 60 each). In each gender category, these athletes were divided into two categories based on injury history: athletes with a history of knee injuries (n = 30) and those without a history of knee injuries (n = 30). The knee injury screening test comprised a visual analog scale (VAS) and anterior knee pain scale (AKPS). Hamstring flexibility and TMS were measured using a Takei Flexion-D digital anteflexion meter and a Takei Back-A analog back muscle dynamometer, respectively. Two-way Analysis of Variance (ANOVA) showed a significant main effect based on injury history on VAS (p = 0.001; F = 96.628; ES = 0.454 [small]) and AKPS (p = 0.007; F = 108,538; ES = 0.483 [small]). The AKPS in males [r = -0.575, p = 0.001] and females [r = -0.304, p = 0.018] showed a negative correlation with flexibility. The Spearman correlation also showed a negative correlation between AKPS and TMS in males [r = -0.227, p = 0.082] and females [r = -0.354, p = 0.006]. This study showed that the AKPS is negatively correlated with flexibility and TMS performance, indicating an increased risk of LBP in the future. Keywords Injury Risk, Knee, Performance, Prevention, Racquet Sports, Sport Injuries 1. Introduction Explosive movements in badminton, such as lunges, jumping, and rapid changes in direction, can cause inadequacy in any segment or joint area, thereby increasing the risk of asymmetry and dysfunction in certain areas [1]. Previous literature has revealed that badminton contributes 1-5% of all sports injuries [2]. This shows that although