Effect of Back Squat Depth on Lower-Body Postactivation Potentiation

Twenty-seven, semi-professional, male rugby union players (mean ± SD, age, 18 ± 2 years; body mass, 87.2 ± 5.4 kg; height, 180.7 ± 5.1 cm) agreed to participate in the study.

Subjects were in the competition phase of their annual training cycle. Their sport training program included a minimum of 3 sessions of resistance training per week, with training loads ranging from 40 to 90% of 1RM. All subjects had experience of resistance training before the study and were free from any upper-body injuries at the time of the study for at least 1 year.

Testing

  • 3RM’s were determined in the Parallel Squat (PS) and Quarter Squat (QS). Parallel Squats were successful if subjects descend until the inguinal fold was lower than the patella (60 – 70° knee joint angle), whereas the Quarter Squat knee joint angle was 135°.
  • Baseline CMJ (BL-CMJ) – jump height, impulse, peak power, and flight time.
  • Conditioning contractions – 1 set of 3 repetitions either PS or QS at 3RM.
  • Post CMJ (POST-CMJ) – jump height, impulse, peak power, and flight time.

IMG_0376

Results

Subjects’ 3RM load for PS and QS were 183.3 ± 17.3 and 200.7 ± 17.3 kg, respectively. All POST-CMJ variables improved significantly compared with BL-CMJ for both PS and QS (p = 0.05). In addition, delta values for PS were significantly higher than QS for all variables examined. Effect size ranged from 0.53 to 1.23 for the BL- to POST-CMJ comparisons, indicating moderate to large effects. For the delta values, the effect was moderate as ES ranged from 0.38 to 0.67.

Conclusion

  • Results show that both QS and PS increase CMJ performance variables (jump height, impulse, peak power, and flight time) and that PS achieves increased performance compared with QS.
  • PSs have been shown to be more effective in engaging the gluteus maximus muscle, an important muscle in all hip extension movements. Training using reduced range of motion can reduce joint mobility, whereas the heavier load allowed by the QS presents a larger risk of back injury and the possibility of changing the power characteristics of the muscle (24).
  • The increased CMJ performance after PS compared with QS found in the study can be attributed to the difference in range of movement between the 2 squat types and the impact it has on work produced by the gluteus maximus and the rest of the relevant muscles. The deeper squat position in PS increases the hip joint angle, resulting in a more stretched gluteus maximus, an important muscle in hip extension. This stretch increases the work required to produce the necessary torque to extend the hip. Furthermore, the mechanical disadvantage of the knee joint during the amortization phase of the PS dictates that more force is required to overcome inertia, further increasing the work performed. The additional work would require higher recruitment of motor units, therefore increasing the excitation potential of the muscle and augmenting its performance during the CMJ.
  • Both QS and PS are widely used in the training setting, and the present study demonstrated that both squat types can provide sufficient stimulus to induce PAP. However, the PS produced superior power performance compared with QS. Therefore, practitioners can use the PS as a PAP conditioning contraction stimulus for acutely enhancing subsequent power performance, while allowing greater range of motion in the hips, knees, and ankles with less compressive loads in the lower back.

Esformes, JI and Bampouras, TM. Effect of back squat depth on lower-body postactivation potentiation. J Strength Cond Res 27(11): 2997–3000, 2013

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