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

Standard skydive from 4 000 m above mean sea level (AMSL) following standard safety recommendations and procedures including, if necessary, standard reserve parachute activation procedures. If necessary for safety, participants are asked to immediately leave the study at will. At 1 500 m AMSL, the participant is asked to begin to slow down the fall rate by increasing the body surface area to the relative wind. At no lower than 1 200 m AMSL, the participant is asked to deploy the main parachute. At main parachute deployment, while maintaining a stable body position with shoulders level to the horizon and unaltered heading, the participant is asked to increase the pitch angle of the long body axis attitude, raising the head, shoulders, and upper body up from the flat belly-to-relative-wind plane to a head-high body position, using any free fall technique the participant is comfortable with - as long as there is NO RISK for an unintentional backflip.