June 6, 2023

Effect of Back Squat Depth on Lower Body Post-activation Potentiation

Discover how the depth of your back squat can impact your lower body post-activation potentiation. Read on to learn about the results of this fascinating study.

Brent Brookbush

DPT, PT, MS, CPT, HMS, IMT

Research Review: Effect of Back Squat Depth on Lower Body Post-activation Potentiation

By Crystal Chariton, MS, LMT, NSCA CSCS, NASM CPT, USAW

Edited by Brent Brookbush DPT, PT, COMT, MS, PES, CES, CSCS, ACSM H/FS

Original Citation: Esformes, J., & Bampouras, T. (2013). Effect of back squat depth on lower-body postactivation potentiation. Journal of Strength and Conditioning Research, 27(11), 2997-3000. ABSTRACT

Why the Study Is Relevant: Increased muscular activity can enhance force generation and subsequent strength and power performance (1), a phenomenon known as post-activation potentiation (PAP). This 2013 study by researchers in the United Kingdom investigated the effects of the parallel squat and the quarter squat (squat range of motion(ROM)) on subsequent counter-movement jump height, peak power, impulse using a jump mat (Smartjump; Fusion Sport, Brisbane, Australia) and flight time. The findings suggest that the parallel squat is superior for increasing PAP for all outcomes measures, despite the quarter squat allowing for approximately 10% greater loads to be lifted. It should be noted that quarter squats were also effective for increasing jump height and flight times over baseline.

Study Summary

Study Design	Experimental randomized, cross-over study
Level of Evidence	IB evidence from at least one randomized controlled trial
Subject Characteristics	Demographics Age: 18 +/- 2 yrs Gender: male Number of participants: 27 Semi-professional rugby union players in the competition phase of their annual training cycle, which included a minimum of three sessions of resistance training per week with loads from 40% - 90% of 1RM Inclusion Criteria: Resistance training experience No upper-body injuries within the past year Current training includes a minimum of three sessions of resistance training per week with loads from 40% - 90% of 1RM Exclusion Criteria: N/A
Methodology	Participants performed the study exercises on two separate occasions- one session for the parallel squat and one session for the quarter squat. Subjects did not eat for 2 hours before the exercise sessions, and they did not drink coffee or alcohol for 24 hours before each exercise session. Subjects were allowed to drink water at will before and during the exercise. During the initial visit, each subject's 3RM for the parallel squat and quarter squat were determined using the National Strength and Conditioning Association guidelines (4). The three repetition maximum indicates failure on the third repetition without loss of proper technique. Subjects attempted 3 repetitions of a load, and if successful, increased the load. A 5-minute rest was allowed between trials. Three to five trials were required for reaching each subject's 3RM. Parallel squat was determined successful when the inguinal fold was lower than the patella, or when the knee joint angle was 60◦-70◦, whereas quarter squat was successful when the knee joint angle was 135◦.
Outcome Measures	Each subject completed a baseline counter-movement jump with arms on the waist. Depth and tempo were self-selected. Performance variables measured during the counter-movement jump included: Jump Height Impulse Peak Power Flight Time A 10-minute rest period was allowed, followed by 1 set of 3 repetitions at 3RM of either parallel squat or quarter squat. The exercises were counter-balanced in a randomized order and performed on separate days. After a 5-minute rest period, subjects completed another counter movement jump. Performance variables measured during the counter movement jump were measured again. Pairwise comparisons were made between pre-squat and post-squat counter movement jump values for all variables for each squat type, and effect sizes for each type of squat were calculated. This is important because the effect size for the parallel squat group were larger than the quarter squat group, with two of the measured variables having over a 1.0 effect size.
Results	Both groups improved in all measures post-intervention, regardless of parallel squat and quarter squat performance. Group means in change in performance variables of counter movement jump, jump height, impulse peak power and flight time increased significantly more post-intervention after the parallel squats than after the quarter squats (p < 0.05). Baseline measurements for both groupscounter-movement jump were: Jump height (in cm) 36 +/- 4 Impulse (in N/s) 247 +/- 22 Peak power (in W) 4,367 +/- 393 Flight time (in ms) 545 +/- 32 Both groups increased all performance variables of interest post-intervention. However, mean change in performance variables of interest in CMJ were significantly greater in the parallel squat group compared to the quarter squat group: Jump height 4.6 +/- 2 Impulse 15 +/- 6 Peak power 285 +/- 109 Flight time 34 +/- 13
Our Conclusions	Back squats performed through a larger range of motion appear to induce greater post-activation potentiation than back squats done through a smaller range of motion (ROM) - despite the load being approximately 10% greater for a back squat performed with reduced ROM. When performing max strength/power super-sets for the lower extremity, and using a back squat as the max strength exercise, it is recommended that the squat is performed with the full available ROM.
Researchers' Conclusions	The parallel squat achieved greater increases in all performance variables compared to the quarter squat, which may be explained by a greater stretch-induced facilitation of the gluteus maximus. Therefore, it is recommended to parallel squat for PAP for subsequent power performance.

The parallel back squat produced greater post-activation potentiation effects and subsequent performance variables based on the results of a post-intervention counter-movement jump.

Caption: The parallel back squat produced greater post-activation potentiation effects and subsequent performance variables based on the results of a post-intervention counter-movement jump.

3RM of parallel back squats produced greater post-activation potentiation (PAP) effects than 3RM of quarter back squats. Performance variables of counter-movement vertical jumps improved after both types of squats, but the parallel squats resulted in greater improvement.

Review & Commentary

This study adds to a significant body of research on post-activation potentiation (PAP), and the use of squats to improve lower extremity power output. Based on the findings of this study, full range of motion is more advantageous than partial range of motion with a heavier load.

This study had many methodological strengths, including:

The study minimized bias by using a cross-over design, randomizing which protocol was used during the first session.
All warm-ups and exercise protocols were standardized, and all outcome measurements were recorded with standardized, calibrated equipment. All participants were given strict guidelines to follow prior to and between testing sessions. Standardized methodology allows for replication of the study to confirm results. Future studies could also mimic the study with a different demographic, or varied loads.
The results of this study fill a gap in the literature regarding the effect range of motion has on PAP. Deeper squats produced greater PAP effects. It would be interesting to attempt a similar study for other movement patterns/body parts.

Weaknesses that should be noted prior to clinical integration of the findings include:

The study used a small, homogeneous sample (n=27) of active, healthy, pain-free male subjects who play semi-professional rugby and who were in the competition phase of their annual training cycles. The results may not be transferable to other populations; future studies should use a sample from a different demographic.
This study did not include appropriate exclusion criteria. All subjects were free from upper-body injuries for at least one year at the time of the study, but nothing was recorded about lower body injuries, which may have had a larger on study results.
The inclusion of electromyography (EMG) and kinematic data during the counter movement jump may have provided additional information. Although the results of this study show a strong correlation for the outcome measures tested, it is not clear why full range of motion squats resulted in better performance.

Why This Study Is Important:

It is the responsibility of every human movement professional to optimize exercise selection and implementation. This study provides information that aids in the refinement of post-activation potentiation protocols; highlighting that full range of motion squats are more advantageous for subsequent increases in performance of the counter movement jump.

How the Findings Apply to Practice:

Back squats performed through a larger range of motion appear to induce greater post-activation potentiation than back squats done through a smaller range of motion (ROM) - despite the load being approximately 10% greater for a back squat performed with reduced ROM. This may be due to deeper squats allowing for more muscle fiber recruitment and greater engagement of the gluteus maximus (1,3). When performing max strength/power super-sets for the lower extremity, and using a back squat as the max strength exercise, it is recommended that the squat is performed with full available ROM. It may be appropriate to consider using "full available range of motion" for the max strength exercise during any PAP super-set.

Related to Brookbush Institute Content

The Brookbush Institute (BI) encourages the full (all normally available) range of motion that can be achieved without compensation or pain. In the case of strength/power supersets (PAP Super-sets), there appears to be no benefit to decreasing range in lieu of greater load.

As a practical education company, the BI will continue to review and compile all available evidence to provide practical evidence-based protocols. Based on this study, BI will add "full available ROM" to PAP protocols used during power training phases.

BI recommends that individuals who desire to improve their performance use a periodized program that starts with endurance/stability and hypertrophy/general strength phases, before progressing to high intensity training phases including max strength and power training and the PAP protocol alluded to above.
- Endurance/Stability: Increase reps or progress exercise (stability)
- Hypertrophy/General Strength: Increase load, increase training volume (small progressions in exercise may be appropriate)
- Max Strength: Increase load, and it may be appropriate to regress exercise to more stable environments
- Power: Increase speed, height or distance

Below are videos related to the exercises described in this study:

Back Squat

Squat Form and Modifications

Box Jumps

References

Caterisano, A., Moss, R., Pellinger, T., Woodruff, K., Lewis, V., Booth, W., & Khadra, T. (2002). The effect of back squat depth on the EMG activity of 4 superficial hip and thigh muscles. Journal of Strength and Conditioning Research, 16, 428-432.
Chiu, L., Fry, A., Weiss, L., Schilling, B., Brown, L., & Smith, S. (2003). Postactivation potentiation response in athletic and recreationally trained individuals. Journal of Strength and Conditioning Research, 17, 671-677.
Fukashiro, S., & Komi, P.V. (1987). Joint moment and mechanical power flow of the lower limb during vertical jump. International Journal of Sports Medicine, 8(1), 15-21.
Harmen, E. & Pandorf, C. (2000). Principles of test selection and administration. In T. Baechle & R. Earle (Eds.), Essentials of Strength Training and Conditioning. Champaign, IL: Human Kinetics.

Questions, comments, and criticisms are welcomed and encouraged.

Effect of Back Squat Depth on Lower Body Post-activation Potentiation

Research Review: Effect of Back Squat Depth on Lower Body Post-activation Potentiation

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