Net joint moments and muscle activation in barbell squats without and with restricted anterior leg rotation

Abstract

Muscle utilisation in squat exercise depends on technique. The purpose of this study was to compare net joint moments (NJMs) and muscle activation during squats without and with restricted leg dorsiflexion. Experienced men (n = 5) and women (n = 4) performed full squats at 80% one repetition maximum. 3D motion analysis, force platform and (EMG) data were collected. Restricting anterior leg rotation reduced anterior leg (P = 0.001) and posterior thigh (P < 0.001) rotations, resulting in a smaller knee flexion range of motion (P < 0.001). At maximum squat depth, ankle plantar flexor (P < 0.001) and knee extensor (P < 0.001) NJM were higher in unrestricted squats. Hip extensor NJM (P = 0.14) was not different between squat types at maximum squat depth. Vastus lateralis (P > 0.05), vastus medialis (P > 0.05) and rectus femoris (P > 0.05) EMG were not different between squat types. Unrestricted squats have higher ankle plantar flexor and knee extensor NJM than previously reported from jumping and landing. However, ankle plantar flexor and knee extensor NJM are lower in restricted squats than previous studies of jumping and landing. The high NJM in unrestricted squat exercise performed through a full range of motion suggests this squat type would be more effective to stimulate adaptations in the lower extremity musculature than restricted squats.

Effects of barbell back squat stance width on sagittal and frontal hip and knee kinetics

“…The net moment of force requirements of the hip and knee joints has been the subject of investigation in numerous squat studies . In terms of transfer to sport performance, kinetic variables such as net joint moment (NJM) ratios between the hip and knee have been proposed as an aiding method in establishing coherence between athletic maneuvers and strength exercises .…”

“…numerous squat studies. [5][6][7] In terms of transfer to sport performance, kinetic variables such as net joint moment (NJM) ratios between the hip and knee have been proposed as an aiding method in establishing coherence between athletic maneuvers and strength exercises. 8 In the sagittal plane, this can be quantified by dividing the peak hip extension NJM by the peak knee extension NJM during an athletic task, thereby creating a hip-to-knee extension NJM ratio.…”

Comparison of Alternative Methods to Improve Weight-Bearing Sagittal Plane Anterior Leg Rotation

“…Individuals with restricted anterior leg rotation may improve their range of motion using selfmassage and stretching of the plantar intrinsic muscles and plantar aponeurosis. Although addition of gastrocnemius strength training using the glute-ham-gastroc raise did not result in further improvements, this exercise alone has been reported to improve anterior leg rotation in an athletic population (9). For barbell squats, increasing anterior leg rotation may increase hip and knee extensor loading by allowing a deeper squat to be achieved (9,17), which facilitates greater hypertrophy quadriceps and gluteus maximus hypertrophy (5,27).…”

Distribution of lower extremity work during clean variations performed with different effort

“…Local and laboratory coordinate systems conformed to the righthand rule with the Z-axis pointing up and Y-axis pointing anteriorly. Joint angles and joint angular velocity were calculated as orientations of the proximal relative to the distal segment using an XYZ Cardan sequence (Chiu, vonGaza, & Jean, 2017;Moolyk et al, 2013). Inverse dynamics was used to calculate net joint moments (NJM) about the ankle, knee, and hip, which were expressed in the distal segments' coordinate system.…”