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

Study Status: Not yet recruiting
Recruit Status: Not yet recruiting
Study Type: Interventional

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

Brief Summary: This study aims to evaluate the use of an aerial human body manoeuvre to reduce the biomechanical load on the neck of a parachutist during the parachute opening, in order to create a basis for future prevention of skydiver neck pain in the parachutist population.

Detailed Summary:

Elevated neck pain prevalence among skydivers is associated with exposure to repeated parachute openings. The parachute opening shock (POS) is a sudden and brutal deceleration of a human being. In skydiving (sport parachuting from aircraft), it slows a free falling skydiver from a velocity >200 km/h to <30 km/h within a few seconds. POS deceleration magnitudes 9-12 times Earth's gravitational acceleration (a dimensionless ratio denoted G) have been measured.⁠ These hard openings were painful, and a number of very hard openings have generated injuries visible to health care systems.⁠ During subjectively normal openings, decelerations measured on the human neck exceed 4 G with initial onset rates (jerks) exceeding 20 G/s. Considering that active skydivers may do ten jumps per day and may accumulate well over a thousand jumps during a parachuting career, these are problematic values. Fighter pilots have suffered neck pain after less accelerative exposure. In the Swedish skydiving population, the neck pain prevalence is 45%, to be compared with a general population estimate of 37%. Recently published data show that skydiver neck muscles are under excessive strain during POS,⁠ and data from our group suggest POS as composed of biomechanically discrete phases. A first phase contains an initial jerk in ventral to dorsal direction, i.e. "pulled backwards", denoted negative Gx, when the skydiver is rapidly rotated from a prone belly-to-earth body position to an upright position. During this phase, the moment arm from the center of mass of the head to the parachute connection point at the shoulders is long and likely to yield a high torque in the neck. The second phase, denoted positive Gz, contains the bulk of POS-deceleration directed caudally to cranially. Entering the second phase with the neck flexed forward from the jerk would put the neck muscles in a clear disadvantage.

  • Magnitudes of decelerations [ Time Frame: 10 seconds ]
    Multidirectional accelerations during ram-air parachute openings expressed in terms of multiples of Earth's gravitational acceleration g using the dimensionless ratio G.
  • Magnitudes of jerks [ Time Frame: 10 seconds ]
    Multidirectional rates of changes of accelerations during ram-air parachute openings expressed in G per second.


    • Original Primary Outcome: Magnitudes of decelerations and jerks [ Time Frame: 10 seconds ]

    Multidirectional accelerations (including decelerations) during ram-air parachute openings expressed in terms of multiples of Earth's gravitational acceleration g using the dimensionless ratio G, and multidirectional rates of changes of accelerations during ram-air parachute openings expressed in G per second.


    Current Secondary Outcome:

    Original Secondary Outcome:

    Information By: Karolinska Institutet

    Dates:
    Date Received: December 7, 2015
    Date Started: November 2016
    Date Completion: December 2017
    Last Updated: August 31, 2016
    Last Verified: August 2016