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Tuesday, June 6, 2023

Ground Reaction Forces in Plyometric Push-Ups

Brent Brookbush

Brent Brookbush


Research Review: Ground Reaction Force Patterns in Plyometric Push Up Variations

By Arran McManus MSc, BSc (Hons), ASCC, FHEA, PGCAP,

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

Original Citation: Koch, J., Riemann, B.L. and Davies, J. (2012). Ground reaction force patterns in plyometric push-ups. Journal of Strength & Conditioning Research, 2220-2227. - ABSTRACT

Why the Study is Relevant: Upper extremity power is enhanced using plyometric exercises that include medicine ball throws and push-ups (1-4). Optimal programming of plyometric exercises should be based on objective measures of intensity; however, most programs are designed using subjective measures. This 2012 study provides objective data on intensity by comparing the vertical ground reaction forces of four plyometric push-up variations. These findings may aid in the optimal selection and progression of plyometric push-ups.

Explosive Phase of the Plyometric Push-Up Exercise - Courtesy of the Brookbush Exercise

Study Summary

Study Design Randomized repeated measures experimental design
Level of Evidence IB Evidence from at least one type of quasi-experimental study
Participant Characteristics
  • Number of participants 22
  • Gender: Male
  • Age +/- Standard Deviation (years): 25.9 +/- 1.3
  • Body Weight +/- Standard Deviation (kilograms): 87.6 +/- 12
  • Height +/- Standard Deviation (meters): 1.80 +/- 0.08

Inclusion Criteria:

  • 3 weekly exercise sessions of 20 minutes or more each for the past 3 months, with 1 upper-body strength training session per week, including exercises such as the bench press, medicine ball throws and push-ups

Exclusion Criteria:

  • Any diagnosed upper-extremity injury or surgery within the past 6 months
  • Plyometric exercises included: clap push-ups and box drop push-ups (BDPs) at varying heights (BDP1 =3.8cm, BDP2 = 7.8cm, BDP3 = 11.4cm).
  • BDPs were as follows:
    • BDP1 was performed with a wooden block on both sides (3.8cm)
    • BDP2 was performed with 2 stacked wooden blocks on each side (7.6cm)
    • BDP3 was performed with 3 stacked wooden blocks on each side (11.4cm)

  • All participants performed a calisthenic systemic warm-up consisting of 10-repetitions of bodyweight squats, static lunges and jump squats
  • Participants then performed the 4 plyometric push-up variations
  • Participants practiced the clap push-up and BDPs exercises until they felt comfortable performing them and qualitative observation yielded proper technique.
  • The order of exercises was randomized for each participant
  • For all 4 variations, participants placed each hand on a separate force plate using self-selected hand placement width
  • At the starting position for each push-up the participant was in the 'up' phase of a push-up with arms fully extended, body in a straight line from head to heels
  • During clap push-ups, participants lowered their chests towards the force plates and then forcefully pushed-up, clapping their hands together while in the air, and landing back on the force plates.
  • The BDPs had two phases; however, the point the hands landed on the force plate until the time the hands left the plate to return to the block was used for measurement.
  • Although the pace of each exercise was self-selected, participants were instructed to perform each repetition with maximal effort and no pause between reps.
  • After completing 4 repetitions of each exercise, participants took a rest of self-determined length (No less than 90 seconds) before the next variation was tested.
Data Collection and Analysis
  • Ground Reaction Force (GRF) data was collected using Motion Monitor acquisition software that converted data (1,000 Hz) from 2 force plates into GRF data; each force independently recorded data for one extremity
  • Intraclass correlation coefficients and standard errors of mean were computed to determine reliability of each dependent variable across multiple repetitions, using a 1-way repeated ANOVA for ground contact time and separate 2-way repeated measures ANOVA or peak vertical GRF, time to peak GRF loading rate, and propulsion rate.
  • Significance was set at p < 0.05
Outcome Measures
  • GRF data collected during the first phase, impact and propulsion from the force plates were analyzed
  • Ground contact time was defined as the length of time that the total vGRF (sum of vGRF under the dominant and nondominant extremities) was >15N
  • Peak vGRF was computed as the time between ground contact and reaching peak vGRF
  • Loading rate was computed as the slope between when the vGRF >50-50N plus one-third body weight
  • The propulsion rate was computed as the slope between when the vGRF decreased <50N plus 1 quarter body weight to <50N
  • Ground contact time for the clap push-up was significantly less than for BDP2 and BDP1.
  • Across all 4 variations, the peak GRF for the dominant limb was significantly greater than for the non-dominant limb.
  • No significant peak vGRF difference were recorded between conditions based on the condition main effect and variation by limb interaction.
  • There was no significant difference for time to peak force among limbs, variation or limb variation.
  • There was a significant variation in loading rate by limb interaction.
  • The loading rate was significantly greater for the clap push-up than for the BDP1, BDP2 and BDP3 .
  • There were no significant differences in propulsion rate between limbs based on the limb main effect or variation by limb interaction.

Intensity Ranking Continuum:

Peak GRF (bodyweight) (low-high):

  1. BDP2 (dominant arm 0.70 +/- 0..02, nondominant arm 0.69 +/-0.02)
  2. Clap push-up (dominant arm 0.69 +/- 0.02, nondominant arm 0.68 +/- 0.02)
  3. BDP3 (dominant arm 0.69 +/- 0.02, nondominant arm 0.67 +/- 0.02)
  4. BDP1 (dominant arm 0.67 +/- 0.02, nondominant arm 0.65 +/- 0.02)

Time to Peak GRF Landing (s):

  1. BDP3 (dominant arm 0.46 +/- 0.03, nondominant arm 0.46 +/- 0.02)
  2. BDP2 (dominant arm 0.43 +/- 0..01, nondominant arm 0.43 +/-0.02)
  3. BDP1 (dominant arm 0.43 +/- 0.02, nondominant arm 0.42 +/- 0.02)
  4. Clap push-up (dominant arm 0.41 +/- 0.02, nondominant arm 0.68 +/- 0.02)

Loading Rate (body weight/s):

  1. Clap push-up (dominant arm 7.26 +/- 0.20, nondominant arm 5.29 +/- 0.26)
  2. BDP3 (dominant arm 6.27 +/- 0.42, nondominant arm 4.64 +/- 0.37)
  3. BDP2 (dominant arm 4.92 +/- 0..28, nondominant arm 4.01 +/-0.24)
  4. BDP1 (dominant arm 4.22 +/- 0.24, nondominant arm 3.5 +/- 0.24)

Propulsion Rate (body weight/s):

  1. Clap push-up (dominant arm -3.32 +/- 0.14, nondominant arm -3.35 +/- 0.14)
  2. BDP3 (dominant arm -2.87 +/- 0.12, nondominant arm -2.84 +/- 0.10)
  3. BDP2 (dominant arm -2.99 +/- 0..11, nondominant arm -2.98 +/-0.11)
  4. BDP1 (dominant arm -2.87 +/- 0.12, nondominant arm -2.92 +/- 0.09)
Our ConclusionsPlyometric exercises should be progressed based on objective data.  This study suggests that plyometric push-ups should be progressed based on intensity from 1.5” to 3.0” to 4.5” box drop push-ups, and then progressing clapping push-ups.
Researchers' ConclusionsUpper-body plyometric exercises vary in force production and loading. Asymmetrical loading occurred in all push-up exercises. The significantly higher propulsion rates and shorter ground contact times identified the clap push-up as the most intense exercise. Although not all values were significant, changing the BDP heights by 3.8cm appears to be appropriate for progressing increases in intensity.

Example of a BDP Push-Up - Courtesy of the Brookbush Institute

Review & Commentary:

The significant differences in ground contact time, loading rate and propulsion rate among push-up  variations suggest that consideration should be given to the intensity of exercise, starting with lower intensity variations and progressing to higher intensities.

This study had many methodological strengths, including:

  • To our knowledge this is the first study to assess kinetic data for a series of plyometric push-up variations.
  • Measurements for ground reaction forces (GRF) were taken using 2 force plates, allowing analysis of asymmetries in limb loading within each variation.
  • The experimental protocol reduced the potential effect of fatigue on findings by randomizing the sequence of exercises, and providing self-determined rest intervals of greater than 90 seconds.

Weaknesses that should be noted:

  • While the fiberglass force plates provided precision in measurement, they are harder than a typical gym floor. This may have altered the participants' landing strategies.
  • No constraints were used for hand placement. This may have resulted in altered upper-body kinematics, which may increase the variability of peak GRF and temporal characteristics.
  • Joint angles were not measured during exercises. Variations in joint angles (chest depth) may affect GRF data (6).

How This Study is Important:

Plyometric exercises are traditionally progressed by increasing intensity. However, intensity is often determined subjectively, which may be vulnerable to coach/athlete bias or inaccuracy (5). To our knowledge, this is the first study to provide objectively measured data on the intensity of plyometric push-ups.

How the Findings Apply to Practice:

This study demonstrated significant differences between 4 plyometric push-up variations based on kinetic data. Propulsion rate varied most among push-up variations, and all variations resulted in asymmetric loading. The clapping push-up had the highest loading and propulsion rate, as well as the shortest ground contact time. Human movement professionals may use this data to build evidence-based plyometric push-up progressions; and maintain awareness of asymmetry if a potential of injury is believed to be present.

Recommended Progression of Plyometric Exercises:

  1. 3.8cm Box Drop Push-Up
  2. 7.6cm Box Drop Push-Up
  3. 11.4cm Box Drop Push-Up
  4. Clap Push-Up

How does it relate to Brookbush Institute Content?

The Brookbush Institute (BI) encourages progressions in all aspects of an exercise program. As suggested by this study, the progression of plyometric/power exercise should be based on objective measurements. Similar to lower-body plyometric exercises (6-13), upper-body plyometric exercise variations exhibit marked differences in intensity. Studies such as this one provide human movement professionals with data to inform the integration and proper progression or regression of these exercises. The BI continues to consider all available evidence in building an integrated model for rehabilitation, fitness and performance and will continue to refine protocols as new evidence becomes available.

Below are a series of upper-body plyometric exercises used at the Brookbush Institute.

Plyometric Box Drop Push-Up Exercise

Alternative Upper-body Power Pushing Exercises:

Chest Pass (chest power exercise)

Sled Push (chest power exercise)


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  2. Davies, G and Matheson, D. Shoulder plyometrics. Sports Medicine Arthroscopy, 9: 1–18, 2001.
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© 2017 Brent Brookbush

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