Free Fall Acrobatics to Reduce Neck Loads During Parachute Opening Shock: Evaluation of an Intervention (ACROPOSE).

introductionNeck pain is a widespread health problem in the skydiver athlete population, epidemiologically linked to repeated exposure to parachute opening shock (POS). During POS, a parachutist is subjected to considerable deceleration forces. This study aims to evaluate the use of preventive free fall acrobatics to reduce the biomechanical load on the neck of parachutists during parachute opening. METHODS AND ANALYSIS: Interventional study with a cross-over, within-subject, repeated measures design. Two consecutive skydives are made on the same day with random ordering of either an 'intervention jump' or a 'control jump'. The intervention jump contains two acrobatic elements prior to main parachute extraction: Reducing parachute deployment airspeed and positioning the human body head high. The primary outcome measure is the magnitude of initial Gx deceleration. All other directions of accelerations will be measured as well, as will magnitudes of multidirectional jerks (rates of changes of accelerations) and lower neck torque. Repeated within group measures analysis of variance will be used to quantify effects, and regression used to test for relationships between the elements of the intervention. ETHICS AND DISSEMINATION: Regional Medical Research Ethics Committee of Stockholm approval 2015/1189-31. The intervention protocol has been systematically prevalidated with an emphasis on participant safety. The study will be conducted in compliance with the Declaration of Helsinki, and its results published in peer-reviewed journals, preferably Open Access, to maximise access for the target athlete population. TRIAL REGISTRATION NUMBER: NCT02625896. Pre-results.