Reproducibility of ballistic push offs parameters from upper or lower limbs
Résumé
Objective : Horizontal ballistic push offs can be used to assess change in force-velocity (FV) parameters up to time of return to play (RTP). As a consequence, the reproducibility of these evaluated parameters should be verified. This study investigated the reproducibility of FV parameters and biomechanical variables measured during push offs performed by upper and lower limbs on a ballistic ergometer.
Material / Patients and Methods : Eleven athletes completed three times both FV protocols the same weekday one week and one month apart. Reaction forces under each hand (or foot) and sled horizontal displacement were recorded while participants pushed-off as fast and strong as possible under several load levels. Maximal theoretical force (F0) and velocity (V0) as well FV slopes were computed. Push off distance, peak and mean force, peak power, mean velocity, Robinson’s asymmetry index and impulse were calculated for each load level. Reproducibility was assessed by means of intraclass correlation coefficient (ICC) and coefficient of variation (CV).
Results : Biomechanical variables were highly reproducible especially after a first session (mean ICC-CV: 0.84-6.4% and 0.83-5.7%, for upper and lower limb, respectively). If upper limb FV parameters had good reproducibility after a first session, those from the lower limb FV were poor. A load level effect was found only for the upper limb asymmetry index while it was below 10% for the lower limb.
Discussion - Conclusion : Results indicated that before using this protocol up to RTP, a familiarization session is needed for both protocols. Ballistic ergometer push offs give a reliable estimation of a possible asymmetry.