Effects of Barbell Squats with Asymmetric Loading on the Joint Moment and Muscle Activity of Lower Limbs

This study aimed to investigate the effects of barbell squats with asymmetric loading on bilateral joint moments and muscle activity of the lower limbs. Twenty fitness athletes were recruited to perform squats under five different conditions. The peak moments in the sagittal plane of the hip and knee joints and the root mean square (RMS) of the gluteus maximus, rectus femoris, and semitendinosus muscles were analyzed bilaterally in the lower limbs, and symmetry was assessed bilaterally using the symmetry index (SI). In the non-dominant side 10% offset load (10%NDOL), the difference in the RMS and moments between the dominant and non-dominant sides was not significant (p > 0.05). Compared with the symmetrical load (SL), the hip and knee SI_M, gluteus maximus, rectus femoris, and semitendinosus SI_RMS were significantly lower on the non-dominant side 5% offset loads (5%NDOL) and 10% NDOL (p < 0.05), and the 10% offset load compared to the 5% offset load difference was significantly lower (p < 0.01). The NDOL reduced the differences in joint moments and muscle activity bilaterally in the lower limbs, with a 10% offset load being more favorable, and the limb SI was significantly negatively correlated with the amount of the offset load in the NDOL. The non-dominant side offset squats are beneficial for balancing muscle strength bilaterally in the lower limbs and improving bilateral strength asymmetry.