Comparison of kinetic variables and muscle activity during a squat vs. a box squat

McBride, JM, Skinner, JW, Schafer, PC, Haines, TL, and Kirby, TJ. Comparison of kinetic variables and muscle activity during a squat vs. a box squat. J Strength Cond Res 24(12): 3195-3199, 2010--The purpose of this investigation was to determine if there was a difference in kinetic variables and muscle activity when comparing a squat to a box squat. A box squat removes the stretch-shortening cycle component from the squat, and thus, the possible influence of the box squat on concentric phase performance is of interest. Eight resistance trained men (Height: 179.61 [+ or -] 13.43 cm; Body Mass: 107.65 [+ or -] 29.79 kg; Age: 24.77 [+ or -] 3.22 years; 1 repetition maximum [1RM]: 200.11 [+ or -] 58.91 kg) performed 1 repetition of squats and box squats using 60, 70, and 80% of their 1RM in a randomized fashion. Subjects completed the movement while standing on a force plate and with 2 linear position transducers attached to the bar. Force anal velocity were used to calculate power. Peak force and peak power were determined from the force--time and power--time curves during the concentric phase of the lift. Muscle activity (electromyography) was recorded from the vastus lateralis, vastus medialis, biceps femoris, anal longissimus. Results indicate that peak force and peak power are similar between the squat and box squat. However, during the 70% of 1 RM trials, the squat resulted in a significantly lower peak force in comparison to the box squat (squat = 3,269 [+ or -] 573 N, box squat = 3,364 [+ or -] 575 N). In addition, during the 80% of 1RM trials, the squat resulted in significantly lower peak power in comparison to the box squat (squat = 2,050 [+ or -] 486 W, box squat = 2,197 [+ or -] 544 W). Muscle activity was generally higher during the squat in comparison to the box squat. In conclusion, minimal differences were observed in kinetic variables and muscle activity between the squat and box squat. Removing the stretch-shortening cycle during the squat (using a box) appears to have limited negative consequences on performance. KEY WORDS force, power, stretch-shortening cycle, strength