## 4 Discussion
### Lower Extremity Kinetics  
A net internal plantar flexor moment was present during both squat descent and ascent. It ranged from 0.20 Nm/Kg to its peak of approximately 0.28 Nm/kg during the descent phase. Peak plantar flexor moments in the current study were comparable to those reported by [PERSON] et al. [10]. Since ankle power was absorbed (i.e., a mean of \(-\)0.10 W/kg) during squat descent, we conclude that the posterior tibial muscles were acting eccentrically to control tibial advancement. Conversely, power generation (i.e., a mean of approximately 0.10 W/kg) during the return phase suggests that the plantarlexors likely contributed to ankle stability and perhaps to knee extension. Frontal and transverse plane moments were small but present yet are relevant to provide stability as individuals were required to maintain their foot progression angle and a foot flat position.  
Small net internal tibofemoral flexor moments were noted at 0% (i.e., 0.14 Nm/kg) and 100% (i.e., 0.18 Nm/kg) of the OHDS, presumably to control knee extension prior to and following the squat. Knee flexion (during descent) and extension (during ascent) resulted in a peak net extensor moment of 0.85 Nm/kg. [PERSON] et al. reported a range of mean peak knee extensor moments (from 0.45 Nm/kg to 0.63 Nm/kg) distinguished by the FMS score [10]. Since we did not distinguish joint motion or joint moments according to the FMS score, our data are not easily comparable to [PERSON] et al. [10]. The knee moment differences may be related to differences in the sample demographics, biomechanical models, and segmental inertial properties used. During the descent phase, power was absorbed (i.e., mean peak of \(-\)1.3 W/kg) as the knee extensors were acting eccentrically, whereas during ascent, the knee extensors were acting concentrically and generating power (i.e., mean peak of 1.3 W/kg). Mean peak valgus (0.28 Nm/kg) and external rotator (0.30 Nm/kg) tibofemoral moments, although small, may reflect the importance of both dynamic (muscular) and static (fascal and ligamentous) constraints during the OHDS. These data are unique to our report since previous research only documented sagittal plane knee moments.  
As the hip flexed during squat descent, a mean peak net extensor moment of 0.76 Nm/kg was generated. This was associated with power absorption (\(-\)0.36 W/kg), confirming the eccentric action of the hip extensor muscles. [PERSON] et al. reported a peak net hip extensor moment of 0.55 Nm/kg [10]. The substantial difference in hip extensor moments between [PERSON] et al. and this report may also be related to differences in sample demographics, the biomechanical models, and the segmental inertial properties used [10; 41]. After reaching the end range of the squat, the hip extensors acted concentrically, generating power (i.e., mean peak 0.50 W/kg). Small net hip adductor moments during squat descent (0.5 Nm/kg) were likely associated with eccentric action of the hip adductors that were used to control hip abduction and perhaps excessive frontal plane motion at the knee [42]. Similarly, small net hip external rotator muscle moments (i.e., mean peak of 0.15 Nm/kg) were generated to control hip internal rotation.