## 1 Introduction  
The squat is a fundamental human movement incorporated into many daily activities and is used by all ages and functional levels. The Overhead Deep Squat (OHDS), a variation of the deep squat with placement of the upper extremities at an end-range ulno-humeral extension and glenohumeral elevation, is a multi-segment movement that requires trunk control, the sequencing of muscular actions, and an available range of motion (ROM) at multiple joints to perform efficiently [1]. Clinical assessment of the OHDS takes place frequently as a part of the Functional Movement Screen(tm) (FMStm), a test battery performed to assess the mobility and stability of individuals in populations, such as, but not limited to, active adults and youth, collegiate athletes, and military service members [2, 3, 4, 5]. The OHDS is one of seven fundamental movements in the FMStm that has been used to screen motor performance and predict performance on the FMStm[6]. Conflicting evidence exists on the predictive validity of the FMStm regarding injuries [2, 3, 7, 8]. Despite this, multiple authors have found good-to-excellent intra-rater reliabilities for rating performance of the components of the FMStm (ICC = 0.87-0.90) among both novice and expert testers with pooled interrater reliability among both novice and experts of 0.81 [8, 9]. Since the OHDS is considered a closed kinetic chain activity, the subaltanic and latorural joints are critical to the proper movement and positioning of proximal segments [10]. It has been shown that the degree of latorural dorsiflexion during squatting movements alters knee frontal and sagittal plane kinetics and kinematics, as well as lumbar and thoracic spine kinematics [10, 11, 12, 13]. Unfortunately, the models used by these studies failed to capture the relationship between the segments of the foot, which may omit information critical to the proper understanding of the OHDS throughout the kinetic chain. Three-dimensional (3D) motion capture allows for the accurate assessment of complex dynamic human movement patterns and has been used to accurately measure kinetics and kinematics in various types of squat forms [10; 11; 14; 15; 16; 17]. The authors were unable to find research using 3D motion capture technology detailing forefoot positioning during squatting. However, in a 3D motion capture study of the knee and hip, individuals with forefoot vars demonstrated increased hip internal rotation during a single leg squat (SLS) [18]. Another study by [PERSON] et al., in which only sagittal plane data were analyzed, found that those who scored better on the OHDS component tended to utilize greater ankle dorsiflexion excursion, peak knee flexion, knee flexion excursion, knee extension moment, peak hip flexion, hip flexion excursion, and hip extension moment when compared to lesser scoring groups [10]. Researchers have also examined gender differences in squat kinematics and kinetics, finding that males display greater peak knee valgus and hip flexion angles, as well as vertical ground reaction forces and peak hip extension moments, while also demonstrating reduced ankle dorsiflexion and hip rotation excursion [19; 20]. Finally, [PERSON] et al. found that those who better performed the OHDS, as scored by the FMS(tm), demonstrated statistically greater hip flexion, knee flexion, knee internal rotation, and ankle dorsiflexion angles compared to those who scored less well [15]. A descriptive dataset including the foot and ankle, which would provide raters with more detailed information in their assessment of the movement pattern, does not exist in the literature [11; 12; 16; 21; 22]. Due to the lack of a normalized comparative dataset that includes more detailed kinematic data on foot movement, evaluation of patients' OHDS compensations is often difficult for clinicians, beyond the dichotomous score.