Myoelectric Activation and Kinetics of Different Plyometric Push-up Exercises

• Number of participants 27
• Gender: Male
• Age +/- Standard Deviation (years): 22.44 +/- 0.31
• Body Weight (kilograms): 76.34 +/- 0.97
• Height +/- Standard Deviation (meters): 1.79 +/- 0.01

Inclusion Criteria:

• Physically active: exercise at least twice per week using routines that includes push-ups

Exclusion Criteria:

• Any diagnosed cardiovascular, neuromuscular, or psychological alterations that could influence performance.

• Prior to testing, participants were measured for height, BMI, and body fat %, by the same researcher.
• Participants did not take part in any strength training prior to testing.
• All participants took part in a standardized warm-up.
• Basic guidance was provided on standardised technique; trials were performed with maximum effort and impact force was controlled/softened.
• Plyometric exercises included: countermovement push-up, fall push-up and jump-push up.
• Each participant performed 2 familiarisation trials and 2 measured attempts.
• A 2-minute rest period was given between attempts.
• The order of exercises were counterbalanced.

GRF Setup:

• Marks were placed on the force plate, and wooden surfaces for hand, knee and foot placement.
• Hand distance was measured as the same distance between the participants' acromion.
• Participants prepared for exercises by resting their dominant hand on a force plate, with feet and knees on wooden blocks at the same height.

Push-Up Protocols:

• Countermovement Push-Up:
  • Starting position: Participants were placed in a prone position, hands and feet on the floor, elbows extended with wrists in a neutral position. The distance between the hands and feet was set so that a vertical line between glenohumeral and metacarpal joints was perpendicular to the floor.
  • Execution: From the starting position, participants flexed elbows and extended arms until the sternum was approximately 3-cm from the floor (descent). Elbows were immediately extended and the arms flexed to return to the starting position. Each attempt consisted of 1 repetition performed at maximal speed.

• Jump Push-Up:
  • Starting Position: Same as Countermovement Push-Up
  • Execution: Participants flexed their elbows until their sternum was approximately 3cm from the floor (descent). The elbows were then extended, arms flexed as hands came off the floor to return to the starting position; another push-up was then completed with a flight- and landing-phase. Participants performed 2 repetitions of the exercise (eccentric phase, concentric phase, flight phase and landing phase) at maximal speed.

• Fall Push-Up:
  • Starting Position: Participants knelt with bent arms (~90˚), extended elbows, and palms facing forwards.
  • Execution: Participants let themselves fall forward and were instructed to minimize the impact as much as possible. With hands placed on pre-set marks, participants lowered their bodies until their sternum was 3 cm from the floor. Elbows were then extended, arms flexed as hands came off the floor to return to the starting position.

• GRF data was collected using a portable force plate containing 4 piezoelectric sensors; each recorded the force produced in 3 spatial directions.

Superficial Electromyography (SEMG):

• SEMG was recorded using a biosignal conditioner with an interelectrode distance of 20mm on the pectoralis major clavicular portion, triceps brachii lateral head, anterior deltoid and external oblique.
• All signals were recorded at a sampling frequency of 1kHz, with SEMG signals acquired throughout the session.
• SEMG was analysed throughout the exercise period, with means calculated for statistical measures.
• Force signals were analysed as below:
  • JPU: The central repetition (end of first flight phase until start of second).

Statistical Analysis:

• A repeated measures multivariate ANOVA (MANOVA) was performed to determine the potential differences in the exercises.
• Significance was set at p < 0.05.

• Impact force (highest GRF during landing phase)
• Maximum force (highest GRF before final propulsive phase)
• Rate of force development (maximum force minus minimum force between impact, divided by,  maximal force minus time to maximal force).
• Rate of impact force (force at beginning of braking phase minus peak impact force, divided by the time to impact force.
• Total time (time necessary to perform one full repetition)
• Time to impact force (time necessary to arrive at peak impact force from beginning of the landing phase).
• Time to maximum force (time to arrive at peak force from the beginning of the braking phase).
• Impact force, rate of impact force development and time to impact force were not calculated in countermovement push-up, as no impact occurred during the braking phase.

• Fall Push-Up:
  • Total time (s): 0.81 (±0.02)
  • Maximum force (N): 485.83 (±11.82)
  • Time to maximum force (s): 0.29 (±0.01)
  • Rate of force development (Ns-1): 1,349.57 (±75.41)
  • Impact force (N): 615.77 (±47.99)
  • Time to impact force (s): 0.0037 (±0.01)
  • Rate of impact force development (Ns-1): 20,811.56 (±2,846.08)

• Jump Push-Up:
  • Total time (s): 0.88 (±0.02)
  • Maximum force (N): 509.37 (±18.23)
  • Time to maximum force (s): 0.38 (±0.02)
  • Rate of force development (Ns-1): 1,146.16 (±102.35)
  • Impact force (N): 491.90 (±32.74)
  • Time to impact force (s): 0.044 (±0.01)
  • Rate of impact force development (Ns-1): 12,598.42 (±1,342.12)

• Countermovement Push-Up:
  • Total time (s): 0.88 (±0.01)
  • Maximum force (N): 517.76 (±12.56)
  • Time to maximum force (s): 0.32 (±0.01)
  • Rate of force development (Ns-1): 1,558.72 (±94.72)

GRF Summary:

• Impact force and rate of impact force were significantly higher in the fall push-up than in the jump push-up.
• Time to impact force was significantly shorter in the fall push-up than the jump push-up.
• Maximum force was significantly higher in the countermovement push-up than in the fall push-up.
• Time to maximal force was significantly longer in the jump push-up than the fall push-up.

Mean/Maximal SEMG Data in Microvolts (mv)(n=27):

• Fall Push-Up
  • External Oblique:
    • Mean 50.27 (±5.68)
    • Max 409.47 (±52.84)

  • Triceps Brachii:
    • Mean 109.21 (±14.07)
    • Max 999.28 (102.66)

  • Pectoralis Major:
    • Mean 141.66 (±22.41)
    • Max 1,699.76 (±109.16)

  • Anterior Deltoid:
    • Mean 226.94 (±28.35)
    • Max 1,677.42 (±105.79)

• Jump Push-Up
  • External Oblique:
    • Mean 34.94 (±3.36)
    • Max 505.96 (±35.06)

  • Triceps Brachii:
    • Mean 53.80 (±5.34)
    • Max 773.84 (±55.29)

  • Pectoralis Major:
    • Mean 61.54 (±5.89)
    • Max 1,522.23 (±69.84)

  • Anterior Deltoid:
    • Mean 93.39 (±7.70)
    • Max 1,327.42 (±89.9)

• Countermovement Push-Up
  • External Oblique:
    • Mean 37.58 (±5.72)
    • Max 635.11 (±84.75)

  • Triceps Brachii:
    • Mean 64.50 (±4.95)
    • Max 862.20 (±29.76)

  • Pectoralis Major:
    • Mean 94.67 (±5.80)
    • Max 1,088.25 (±81.15)

  • Anterior Deltoid:
    • Mean 151.83 (±8.17)
    • Max 1,362.69 (±79.10)

SEMG Summary:

• Significantly greater muscle activity of the
• on the pectoralis major, triceps brachii, anterior deltoid and external oblique was recorded in the fall push-up than the jump push-up.
• Significantly higher maximum EMG values of the pectoralis major and triceps brachii were recorded in the fall push-up than in the countermovement jump push-up.
• Significantly higher maximum EMG values for the pectoralis major were recorded in the jump push-up than in the countermovement jump push-up.
• The average EMG values for the pectoralis major and anterior deltoids were significantly lower in the jump push-up than in the countermovement push-up.