The back squat is widely used in strength training programs. Alternatively, the belt squat has been gaining popularity since it loads the weight on the hips, as opposed to the shoulders and spine. The purpose of this study was to determine whether using a belt squat would result in less lumbar extensor activation while providing similar excitation of other prime mover and stabilizer musculature. Ten participants (9 males, 1 female; age 29.3 ± 4.9 years; body mass 96.2 ± 17.8 kg) who regularly trained both belt squats and back squats performed three sets of 5 repetitions with 100% bodyweight for each exercise. Peak and integrated muscle activity was calculated and normalized to a maximum voluntary isometric contraction. A one-way ANOVA (p < 0.05) was used to compare conditions. Belt squatting decreased lumbar erector impulse (45.4%) and peak (52.0%) activation as compared to the back squat. Belt squatting did not alter activation of the lower extremities except for a decrease in the gluteus maximus (35.2% impulse and 32.1% peak), gluteus medius (54.1% impulse and 55.2% peak). Furthermore, belt squatting reduced activation of the rectus abdominus (44.3% impulse; 31.1% peak), and external obliques (45.8% impulse; 53.7% peak) as compared to back squatting. Our results suggest belt squatting provides similar muscular demands for the quadriceps, hamstrings, and plantar flexors, but is less demanding of trunk stabilizers, and gluteual muscles. Belt squats may be a suitable alternative to back squats in order to avoid stressing low back or trunk musculature.