Inconsistent anticipatory postural adjustments (APAs) in rugby players: a source of injuries?

International audienceWe are developing since 2010 with Thalesand the Fédération Française de Rugby (FFR) M-Rex, anew kind of rugby scrum simulator. The study questionedwhether it could improve safety and protect players frominjury by using it as a tool for training/coaching the packs.To explore the anticipatory postural adjustments(APAs) during the engagement of the ruck, because thesepredictive neck and back muscles contractions protectthe spinal cord at the time of impacts, which is crucial toprevent injuries.We quantified the kinematics and the EMGactivities in high-level front row players during their initialengagement, when scrummaging with M-Rex. All studieswere performed with one player interacting with the robot,at first, and then with the three players acting together.For most of the tested high-level players, theAPA latencies were highly variable from trial to trial eventhough the engagement resulted in similar impacts. Attime, the onset of the electromyography activity in theneck and back muscles showed latencies inferior to 50 msor even close to zero prior to the impact , which renderedmuscle contractions inefficient as APAs. We were alsounable to identify clear muscular synergies underlying theAPAs because of their great variability on a trial-to-trialbasis. Finally, the APAs were not related to the amplitudeof the ensuing impact and were asymmetric in most trials.All these characteristics held true, whether the player wasplaying alone or with two other frontline players.Our result suggest that APAs should besystematically tested in high-level rugby players as wellas in any high-level sport men at risk of neck and backinjuries. Because APAs can be efficiently trained, our studypaves the way to design individual position-specific injuryprevention programme