[QUOTE=The_KM;532520]When you use something like that, core and lumbar stabilizing muscles are inactivated which will lead to atrophy. Sounds like no bid deal, but you'd be surprised how active the core and lumbar are in most lifts. A key component to multi-joint lifts is a developed core.[QUOTE]
There are different opinions about this subject.
The Journal of Strength and Conditioning Research: Vol. 13, No. 4, pp. 384–388.
The Use of Lumbar-Supporting Weight Belts While Performing Squats: Erector Spinae Electromyographic Activity
JEFFREY A. BAUER and CORY CARTER
University of Florida, Gainesville, Florida 32611
University of Memphis, Memphis, Tennessee 38152
This study sought to analyze the effects of subjects' wearing weightlifting lumbar support belts on surface electromyographic recordings of the erector spinae muscle group while the subject executed parallel squats. Ten healthy college-age men with weightlifting experience participated in this study. Participants completed a total of 6 repetitions of high-bar parallel back-squats at loads equaling 60% of their 1 repetition maximum. Experimental conditions required subjects to perform 6 squats, 3 while wearing a belt and 3 without. Electromyographic electrodes recorded muscle activity at 800 Hz on both the right and left erector spinae at the lumbar (L3–L5) and thoracic (T5–T7) regions during all lifts.
The results indicate that subjects' mean erector spinae activity was greater (p < 0.0125) in the lumbar region of the spine when wearing weight belts (*258 SD; 69.0 analog-to-digital units) during squatting exercises than the mean activity in subjects who were not wearing weight belts (*235 SD; 71.3 analog-to-digital units).