Effectiveness of suspension seats in maintaining performance following military high-speed boat transits.

OBJECTIVE: The aim of this study was to investigate whether suspension seats (SS) fitted to rigid inflatable boats (RIB) could help maritime boarding teams maintain running performance during the high-risk posttransit phase. BACKGROUND: High-speed RIB transits have been reported to cause reductions in the running performance of boarding teams posttransit. METHOD: In this experiment, two pairs of teams completed a 3-hr transit in either calm or rough seas (calm, 5 vs. 5; rough, 6 vs. 6) in an RIB fitted with either fixed (FS) or Suspension seats (SS). Exhaustive shuttle run distance was measured pre- and immediately posttransit. Transit heart rate and perceived exertion (RPE) were measured and deck and seat pan acceleration recorded; the latter were reported as impacts count and peak magnitude. RESULTS: Distance run was reduced for the FS teams following both transits (calm,-250 m,-20%, p < .07; rough, -398 m, -26%, p < .05), whereas it was unchanged for the SS teams. All transit heart rates and RPE indicated light exertion levels. Seat pan impacts were similarly reduced during the calm transit (FS, -42%; SS, -30%); however, during the rough transit, the SS was more than twice as effective (FS, -32%; SS, -71%). Peak impact magnitudes were reduced by the SS (calm, -38%; rough, -57%) and amplified by the FS (calm, +3%; rough, +28%). CONCLUSION: Suspension seats effectively maintained posttransit running performance by reducing magnitude of the vertical shocks imposed on the passengers. APPLICATION: High-speed RIB transits followed immediately by high-intensity activity are intrinsic to contemporary maritime operations; suspension seats can maintain post-transit physical performance, thereby enhancing safety and operational effectiveness.

Physiological consequences of military high-speed boat transits.

The purpose of this study was to investigate the consequences of a high-speed boat transit on physical performance. Twenty-four Royal Marines were randomly assigned to a control (CON) or transit (TRAN) group. The CON group sat onshore for 3 h whilst the TRAN group completed a 3-h transit in open-boats running side-by-side, at 40 knots in moderate-to-rough seas, with boat deck and seat-pan acceleration recorded. Performance tests (exhaustive shuttle-run, handgrip, vertical-jump, push-up) were completed pre- and immediately post-transit/sit, with peak heart rate (HRpeak) and rating of perceived exertion (RPE) recorded. Serial blood samples (pre, 24, 36, 48, 72 h) were analyzed for creatine kinase (CK) activity. The transit was typified by frequent high shock impacts, but moderate mean heart rates (<45% HRpeak). The TRAN group post-transit run distance (-219 m, P < 0.01) and vertical-jump height (5%, P < 0.05) were reduced, the CON group showed no change. The TRAN group post-transit test RPE increased (P < 0.05), however, HRpeak was similar for each group (98%). Post-transit CK activity increased in the TRAN group up to 72 h (P < 0.01) and also, but less markedly, in the CON group (24 and 48 h, P < 0.05). Post-transit run and jump performances were reduced despite mean transit heart rates indicating low energy expenditure. The greater TRAN CK activity suggests muscle damage may have been a contributory factor. These findings have operational implications for Special Forces/naval/police/rescue services carrying out demanding, high-risk physical tasks during and immediately after high-speed boat transits.

Survey of spatial disorientation in military pilots and navigators.

BACKGROUND: The direction of future spatial disorientation (SD) research and training is shaped primarily by the outcome of formal investigation of aircraft accidents and incidents. However, another source of vital information is aircrews' experience of SD that does not result in reported incidents. METHODS: A short postal SD survey was distributed to 5 Naval Air Squadrons, 22 Joint Helicopter Command Units, and 7 Royal Air Force stations in the United Kingdom. There were 752 questionnaires, including responses from 562 pilots and 149 navigators, that were returned. RESULTS: Analysis was conducted primarily on the pilot data. The most frequently experienced SD episodes were "the leans" (by 92% of respondents), loss of horizon due to atmospheric conditions (82%), misleading altitude cues (79%), sloping horizon (75%), and SD arising from distraction (66%). In general, the frequency of SD episodes and ratings of severity of the worst ever SD episode were positively related to flying experience (p < 0.05). Overall, pilots who had received in-flight SD training reported more episodes of SD than those who had not participated in this training (p < 0.05). Differences in types of SD experienced were found between aircraft categories, e.g., more episodes of SD during night vision goggle use were reported by rotary-wing pilots compared with fast-jet aviators (p < 0.05). CONCLUSIONS: This preliminary survey has shown that SD is still a significant hazard of military flying. Overall, this study shows that the postal questionnaire is a useful tool for assessing how SD training and experience may benefit the recognition of situations that may cause SD. However, it is difficult to access those situations where aircrew were truly disorientated.