Hecker, KA, Carlson, LA, and Lawrence, MA. Effects of the safety squat bar on trunk and lower-body mechanics during a back squat. J Strength Cond Res XX(X): 000–000, 2018—The purpose of this study was to determine whether the safety squat bar (SSB) alters the mechanics and muscle activity of a back squat compared with a standard barbell (ST). Motion and muscle activation of the trunk and lower extremity were measured while 12 competitive powerlifters (8 males, 4 females, age 31.5 ± 6.3 years, body mass 88.1 ± 20.7 kg, competitive lifting experience 3.3 ± 2.8 years) squatted 3 sets of 5 repetitions at 75% of their 3 repetition maximum (3RM). Mean muscle activity and peak joint flexion angles were measured for the trunk and one lower extremity. A repeated-measures analysis of variance (p = 0.05) revealed an 11.3% decrease in 3RM when using the SSB. When using the SSB, there was a decrease in trunk and hip flexion (7.3 and 5.7° respectively) and a 50.3% increase in lower trapezius activation. However, using the SSB decreased activation of the rectus abdominis (46.3%), medial hamstring (17.1%), lateral hamstring (15.1%), vastus lateralis (9.3%), and medial gastrocnemius (18.8%). Squatting with the SSB resulted in a more upright trunk angle, which places less stress on the lower back, a commonly injured area when squatting. Decreases in lower-extremity muscle activation are likely due to the decreased load used, suggesting that the SSB may not be as effective as a standard bar to increase lower-extremity strength. However, the increase in the lower trapezius with the lighter load suggests that midback musculature may be challenged more by the SSB than a standard barbell.
1Department of Exercise and Sport Performance, University of New England, Biddeford, Maine;
2Department of Physical Therapy, University of New England, Portland, Maine; and
3Center for Excellence in the Neurosciences, University of New England, Biddeford, Maine
Address correspondence to Michael A. Lawrence, Mlawrence3@une.edu.