The test–retest reliability of bilateral and unilateral force plate–derived parameters of the countermovement push-up in elite boxers

Context: Maximal power describes the ability to immediately produce power with the maximal velocity at the point of release, impact, and/or take off—the greater an athlete’s ability to produce maximal power, the greater the improvement of athletic performance. In reference to boxing performance, regular consistent production of high muscular power during punching is considered an essential prerequisite. Despite the importance of upper limb power to athletic performance, presently, there is no gold standard test for upper limb force development performance. Objective: To investigate the test–retest reliability of the force plate–derived measures of countermovement push-up in elite boxers. Design: Test–retest design. Setting: High Performance Olympic Training Center. Participants: Eighteen elite Olympic boxers (age = 23 [3] y; height = 1.68 [0.39] m; body mass = 70.0 [17] kg). Intervention: Participants performed 5 repetitions of countermovement push-up trials on FD4000 Forcedeck dual force platforms on 2 separate test occasions 7 days apart. Main Outcome Measures: Peak force, mean force, flight time, rate of force development, impulse, and vertical stiffness of the bilateral and unilateral limbs from the force–time curve. Results: No significant differences between the 2 trial occasions for any of the derived bilateral or unilateral performance measures. Intraclass correlation coefficients indicated moderate to high reliability for performance parameters (intraclass correlation coefficients = .68–.98) and low coefficient of variation (3%–10%) apart from vertical stiffness (coefficient of variation = 16.5%–25%). Mean force demonstrated the greatest reliability (coefficient of variation = 3%). In contrast, no significant differences (P < .001) were noted between left and right limbs (P = .005–.791), or between orthodox or southpaw boxing styles (P = .19–.95). Conclusion: Force platform–derived kinetic bilateral and unilateral parameters of countermovement push-up are reliable measures of upper limb power performance in elite-level boxers; results suggest unilateral differences within the bilateral condition are not the norm for an elite boxing cohort