Walailak Procedia 2018; 2018(3): hs226 http://wjst.wu.ac.th/index.php/wuresearch การประชุมวิชาการระดับชาติ “วลัยลักษณ์วิจัย” ครั้งที ่ 10 วันที ่ 27-28 มีนาคม 2561 หัวข้อวิทยาศาสตร์สุขภาพ Relationship between Trunk Stabilizer Muscle Strength and Frontal Hip and Knee Angles during Single-Leg Squat in Female Individuals Janmai Nuchkham, Sirikarn Somprasong * and Komsak Sinsurin Faculty of Physical Therapy, Mahidol University, Nakhon Pathom 73170, Thailand sirikarn.som@mahidol.ac.th Abstract Objective: The purpose of this study was to investigate correlation between trunk stabilizer muscle strength and the frontal hip and knee angles during single-leg squat. Method: Fifteen women (19-27 years old) participated in this study. All participants were right leg dominance. Trunk stabilizer muscle strength was measured. A Vicon™ Nexus system with 10 cameras were used to examine the frontal hip and knee angles. Single-leg squat test was used dominant leg. Spearman’s rank correlation was used to determine the correlation between the level of lumbar stabilization exercise and the frontal hip and knee angles. Besides, Pearson’s correlation was analyzed the correlation between trunk muscle strength which was measured by handheld dynamometer and the frontal hip and knee angles. Results: Muscle strength of right external oblique abdominis showed a negatively significant correlation with the frontal hip angle (r = -0.61, p = 0.02). The level of lumbar stabilization exercise had no correlation with the frontal hip and knee angles. Conclusion: This study demonstrated that trunk stabilizer muscle strength associated with the frontal hip during single-leg squat. Further study should consider the effect of trunk stabilizer muscle on lower extremity biomechanics. Keywords: Trunk stabilizer trunk muscle strength single-leg squat frontal hip angle frontal knee angle Introduction Trunk stability is an importance for preventing lower extremity injury [1] and the instability may play a role as the risk of lower extremity injury in female [2,3]. Impaired core proprioception and deficits neuromuscular control of trunk can predict the knee injury [4,5]. Based on anatomy, trunk muscles connect to the lower extremity muscles [6]. Therefore, either trunk muscle or lower extremity muscle has a problem, then, may effect each other. An improvement of trunk muscle activation may be able to improve the lower extremity movements and stability. Moreover, movement of the pelvis and trunk can influence the moments at the knee [7]. Willson et al evaluated the association between core strength and lower extremity alignment during single-leg squats. The lower extremity alignment present by frontal plane projection angle (FPPA) of knee. The FPPA is an angle between the line from ASIS and mid tibiofemoral joint, and the line from mid tibilofemoral joint and mid ankle joint. They used handheld dynamometer for measure the core muscle strength. The result showed that trunk extensor and trunk lateral flexor muscles strength fair associated with FPPA [8]. In addition, the study about correlation of core muscle strength and frontal plane alignment of lower extremity during single-leg squat found that sidelying plank has fair correlated with the peak FPPA in healthy female. The negative FPPA represented genu valgus