Characteristics of 'low risk' and 'high risk' dives by young adults: risk reduction in spinal cord injury

Study design: To establish benchmark normative data for dive entries perfor med by young adults of the age range most likely to sustain a diving spinal cord injury. Data acquired from analysis of the dives performed, along wit h survey information, were used to determine which factors make the most co ntribution to the level of risk in diving. Objectives: To identify influential variables which could contribute to ris k of spinal cord injury for each of four types of dives. The types of dives investigated were: dive entries from deck level to tread water (Treadwater ); deck level to swim 25 m (Deck); starting block height to swim 25 m (Bloc k); and a running dive entry to swim 25 m (Running). Setting: Victoria, Australia. Methods: Ninety-five first year university students (average age 19.9 years ) performed three or four dives which were video-recorded for later analysi s. Maximum depth reached was used as an indicator of risk, and velocity at maximum depth, distance at maximum depth, angle of entry and flight distanc e were measured for each dive. Participants also completed a questionnaire designed to elicit information about their swimming and diving background. Unlike previous diving studies, participants were recreational rather than competitive swimmers. They were not aware that the dive was the focal point , assuming that the researchers were investigating their swimming and tread water ability. Results: A stepwise multiple regression was applied to predict depth for ea ch dive condition, and demonstrated that four variables were able to accoun t for 56% of the variance for Treadwater, 68% for Deck; 73% for Running and 79% for Block. In all conditions involving swimming after the dive tie Dec k, Block and Running), beta weights showed that distance at maximum depth h ad the greatest influence on the depth of a dive. Flight distance and angle of entry were the next most influential variables. For the Treadwater cond ition, beta weights showed angle of entry was the most influential variable , followed by velocity at maximum depth, distance at maximum depth and swim rank. Conclusion: It is recommended that divers strive to surface in as short a d istance as possible by maximising flight distance and aiming for a low entr y angle. Implementation of steering-up techniques will assist in minimising dive depth. Sponsorship: This study was supported in part by a grant from the Victorian State Government Department of Human Services, Grampians Region.