Equating Unilateral and Bilateral Half-Squat Loads: Neuromuscular and Kinetic Analysis

This study aimed to develop predictive equations for unilateral (1-leg) half-squat exercise loads that would elicit equivalent neuromuscular activation, velocity, and force outputs as bilateral (2-leg) half-squat exercise loads. Twelve male soccer players (age 22.9±1.8 y, stature 1.8±0.1 m, and body mass 76.5±6.2 kg) performed both 1-leg and 2-leg half-squats using a Smith-machine. Surface electromyography of vastus lateralis and vastus medialis, barbell velocity and force outputs were measured across incremental loads. Linear regression analyses were conducted to develop predictive equations for 1-leg loads that would match 2-leg exercise outcomes. Three predictive equations were developed: (1) Equivalent muscle activation: 1-leg external load=50% of 2-leg external load -2 kg (r=0.923-0.997, p<0.05). (2) Equivalent barbell velocity: 1-leg external-load=71% of 2-leg external load -17.6 kg (r= -0.916 to 0.994, p<0.05). (3) Equivalent force-output: 1-leg external load=41% of 2-leg external load - 28 kg (r=0.937-0.998, p<0.05). This preliminary investigation provides initial predictive equations for equating unilateral and bilateral half-squat exercises, though validation on independent populations remains necessary. These tools enable practitioners to estimate equivalent loads between exercise modalities using a single one-repetition maximum assessment, facilitating targeted training and rehabilitation program development through accurate load prescription and performance comparisons. Further research is needed to validate these equations on large population and in different sports.