Boat Instrumentation Feasibility Study to Assess Biomechanics of Competitive Surf Lifesavers During Inflatable Rescue Boat Activities: Technical Report #5 to Surf Life Saving New Zealand (SLSNZ)
Diewald, SN; Hume, P; Wilson, BD; Wooler, A; Merrett, R; Grobleny, M; Keeley, L; Reay, S; Smith, V
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Background: Only two studies to date have investigated loads experienced on IRBs during operation. Purpose: To pilot a data collection system for acceleration and video footage of the IRB and crew on water, to be used in subsequent studies of IRB‐related activities. Methods: A pair of experienced (national champion) surf lifesavers were utilised for this study (an IRB driver and a crew member). The crew member was instrumented with three inertial measurement sensors; left tibia, right tibia, and sacrum. An IRB provided by Sunset Beach Surf Life Saving Club was instrumented with 3 GoPro cameras in order to get a view of the entire IRB, crew member lower extremity, and surf conditions. The surf lifesavers performed typical IRB maneuvers utilized during patrol and/or competition. The collected sensor and video data were imported and analysed for feasibility. Results: The goal of the analysis of the feasibility study was to first identify if the sensors and video footage captured the necessary information. In order to identify tasks in the IMU data, time stamps were able to be matched with the video footage of interest. Camera footage was useful however locations of the cameras may need to be modified in future studies. Successful collection of accelerometer and gyroscope data demonstrated a need to investigate the vibration exposure of surf lifesavers while operations IRBs. Through a frequency analysis approach, identifying the power spectrum densities of the accelerometer and gyroscope signal may enable the comparisons of vibrations during different IRB crewing tasks under different techniques and body positions. This technique may help to identify age‐ and gender‐ specific load prescriptions in order to minimize the risk of developing low back pain. Discussion: Only the ±16 g accelerometer was analysed as this was a feasibility pilot to assess if the method would work. Future studies should use inertial measurement sensors with an acceleration range of ±100g sampling at 500 Hz. The weather and water conditions were mild; thus future studies are recommended to determine feasibility in varying conditions. Due to the difficulty of assessing kinematics from the GoPro footage, future studies should investigate the different positioning of the crew members in a lab environment to assess potential injury mechanisms while varying IRB orientations. Conclusions: Inertial sensors attached to surf lifesavers at the sacrum while operating IRBs may help quantify loads and frequencies associated with common injuries; such as, lower back pain and soft‐tissue ankle injuries. Future research should standardise water‐based maneuvers to compare across populations and conditions. Signal analysis techniques should be investigated under different water and weather conditions.