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Background Sport parachuting is a dangerous recreational activity for which available literature appears unsatisfactory to form a basis for injury prevention.

 Aim Overall: Explore some risk factors in sport parachuting. Study I: Identify fatal incident and injury mechanisms for skydiving (sport parachuting from aircraft). Study II: Identify fatal incident and injury mechanisms for BASE jumping (sport parachuting from fixed objects) for each of the four fixed object types B-A-S-E (building, antenna, span, earth). Study III: Identify non-fatal incident and injury mechanisms for skydiving. Study IV: Evaluate the validity of a compulsory reporting system among active skydivers. Study V: Explore some aspects of the Swedish skydiving culture and its relation to injury risks and injury reporting. Study VI: Describe the mechanism of incident and injury for a free fall shoulder dislocation.

Methods Descriptive epidemiological studies of (I) fatal injury events in Swedish skydiving, (II) fatal injury events in BASE jumping worldwide, and (III) non-fatal injury events in Swedish skydiving. Self-report survey of (IV) Swedish skydivers to measure: Sensitivity, as the proportion of injury events fulfilling the reporting criterion that were actually reported; Specificity, as the proportion of false positives in relation to the defined gold standard. Content analysis of (V) Swedish skydiving participant narratives. First-person narrative and free fall video recordings (VI) of one case.

Results Overall: Risk factors associated with “free fall” flight of the human body and recreational usage of parachutes were described. Study I: Fatal risk factors in skydiving included student instability in free fall, leading to unstable parachute activation with subsequent line entanglement or parachute activation failure. Unintentional water landings also contributed to fatalities. Every fourth skydiving fatality survived impact and died during transports or in hospitals. Study II: Fatal risk factors in BASE jumping included parachutist free fall instability, miscalculation of free fall acrobatics, deployment failure by the parachutist, pilot chute malfunction and parachute malfunction. In cliff jumping (BASE object type E), parachute opening towards the object jumped with subsequent collision was a frequent factor. Poor visibility, strong or turbulent winds, cold and water also contributed to BASE jumping fatalities. Study III: Non-fatal risk factors in skydiving included experience level and type of student-training system. The lower extremities, spine and shoulders were important regions of injury. The most serious injuries were seen in experienced skydivers. Study IV: The overall sensitivity of the skydiving injury reporting system was 0.37 (95% confidence interval (CI) 0.24-0.51). With non-minor injuries as the target for reporting, the sensitivity was 0.67 (95% CI 0.43-0.85). No significant effect on reporting was found for gender, age, license level, years in the sport, total number of jumps or club affiliation. The specificity was 0.91 (95% CI 0.83-0.95). Study V: It is suggested that Swedish skydiving culture is carried by the local club; not the national association. Skydiving culture at the local drop zone and formal and informal hierarchical structures among skydivers may be what really decides how rules are enforced, risk-taking behavior is seen, and if incidents and injuries are reported. Study VI: The free fall airstream forces were in this case strong enough to dislocate a shoulder joint, which has safety implications that should be considered by participants and medical doctors performing precourse examinations.

Conclusion A number of risk factors in sport parachuting are described. Some technological, training and regulatory interventions are suggested to increase safety.