Changes in muscle activation in response to abdominal bracing and stabilization belt use during a loaded squat

This research investigated the effects of trunk stabilisation on trunk and lower extremity muscle activity during a loaded barbell squat. Twenty-eight healthy male subjects (mean age 22.1 ± 1.9 years) performed three squatrepetitions at 75% predicted one-rep-max load using four trunk stabilisation conditions: no bracing/belt (NoSS), abdominal bracing (AB), stabilization belt (StB), and bracing/belt combined (AB+StB). Subjects first performed NoSS; the remaining conditions were randomised. Lower quarter surface electromyography (EMG) was obtained from six muscles bilaterally; external oblique, internal oblique, iliocostalis lumborum, gluteus maximus, vastus lateralis and biceps femoris. A within-subjects 2(phase)x4(stabilisation strategy) ANOVA assessed root-mean-square EMG amplitude. Tukey's tests located significant differences. Abdominal muscle activity was significantly greater during AB conditions, AB and AB+StB, versus non-AB conditions, NoSS and StB (p < .001; ηp² = 0.31-0.48). Lumbar and lower extremity muscle activity was not significantly altered by AB, StB or AB+StB. Lumbar extensor and quadriceps activity were significantly greater during squat ascent versus descent (p < .01; ηp²  0.23-0.43). Incorporating AB during squatting increased abdominal muscle activity, both with and without StB use. The StB use alone did not alter muscle activation. These findings indicate that AB, with or without StB use, is effective in enhancing abdominal muscle engagement during the loaded barbell squat.