Effects of Squat Amplitude on pelvic tilt and Tibial Inclination

Strength training is commonly performed at two different knee flexion amplitudes: partial (to 90 degrees) or total (to 140 degrees). During these amplitudes, both the pelvis and the tibia are moved to ensure control of the center of gravity and displacement of the external overload. Forward or backward movement of the pelvic tilt may indirectly influence the internal load on the spine. Objective: To measure the effect of squat amplitude on pelvictilt and tibia inclination. Eighteen male subjects (age: 26 ± 6 years, height: 178 ± 7 cm, total body mass: 81.3 ± 11 kg, resistance training experience: 5 ± 4 years) were evaluated. Pelvic tilt and tibial inclination were measured by a digital inclinometer (Max Measure, USA, accuracy: ± 0.02°, resolution: 0.05°) during isometric squatting at partial and full amplitudes. The digital inclinometer was fixed on the sacrum and on the tibia, with aneutral spine position. A paired student t-test and a significance of 5% were used. There were significant differences in pelvic tilt between partial and full amplitudes (+ 32.4° ± 10.9 and -21.7° ± 12.3, respectively, P<0.001). Maximum tibial inclination values were not significantly different between partial and total amplitudes (19.1 ± 6.6 and 20.1 ± 7.4, respectively, P = 0.225). It was concluded that the partial squat position produces anterior pelvic tilt while the full squat produces backward pelvic tilt. Inclination of the tibia is similar in both amplitudes of the squat.