Physiological consequences of military high-speed boat transits

Abstract

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.

An experimental investigation into whole body vibration generated during the hydroelastic slamming of a high speed craft

“…Peak acceleration and peak duration are clear and true indicators of the acceleration magnitude on the human body after applying the W b frequency weighting. Furthermore, peak acceleration can be compared to the peak counting method for assessing the WBV from HSC with forward speed, such as Allen et al (2008) and Myers et al (2011). Peak counting can be compared to peak acceleration because a reduction in peak acceleration would indicate that the peak counting magnitudes would also reduce; however, the non-linear response of a HSC is not considered.…”

“…The crest factors were above 6; this meant VDV was used instead of RMS and the zaxis values were 48.51 ms -1.75 and 25.90 ms -1.75 in sea states two and three, respectively. Myers et al (2011) measured the acceleration on board a military HSC at 40 knots in a sea state of two to three and the VDV for a 3 hour transit was 57.05 ms -1.75 on the deck. This is clear evidence that the vibration within these craft regularly exceeds the ELV and a solution, or combination of solutions, must be found.…”

“…Ensign et al (2000) also reported that the psychological injuries include; annoyance, fatigue, anxiety, loss of visual accuracy and reduced hand-eye coordination (the latter two could be considered a combination of both physiological and psychological effects). Myers et al (2011) demonstrated a three hour transit at 40 knot in HSC will reduce the physical performance of the crew (including run distance and vertical jump height). Therefore, reducing boat motion and human exposure to vibration can reduce the risk of injury, provide a better working environment and increase the crew's effectiveness during and after transit.…”

Neuromusculoskeletal Dynamic Modelling of Human Movement in Motion Environments

“…Exceeding speeds of 40 knots, the hull constantly experiences vertical shocks of up to 10 g, occasionally reaching 20 g, as a result of hull separation from the water, as shown in Figure 1.1. These shocks are potentially higher than those a jet pilot experiences upon ejection [1,2]. As a result, HSC transits are among the harshest operating environments as compared to any other mode of transport.…”

“…These rapid eccentric muscle contractions cause localized fatigue and muscle damage indicated by elevated creatine kinase levels up to 72 hours post-transit, which is consistent with self-reported pain and soreness in occupants. Creatine kinase is a muscle enzyme involved in energy production that is commonly assayed in blood tests for indications of tissue damage [1,2]. The result is a significant reduction in physical performance: decreased jump height, running capability, and power output.…”