Marine High-speed Craft Coxswain Workload

Abstract

Marine high-speed craft (HSC) are used extensively by military and civil organizations to complete vital tasks, often involving long transits in rough sea conditions. In contrast to larger vessels, driving an HSC in rough sea conditions requires the coxswain to make constant manual adjustments to speed and heading, also these conditions result in extreme craft motions, particularly high-levels of repeated mechanical shock (> 20g) that is counteracted through predominantly eccentric muscle actions. These combined stressors potentially result in the coxswain's workload being greater than their passengers. This increased workload may degrade coxswain ability (e.g. situational awareness), potentially compromising operational safety and performance. PURPOSE: To assess the differences in workload between coxswains and passengers a pilot study was completed measuring heart rates during operational transits in calm and rough sea conditions. METHODS: Experienced coxswain (n = 4) and passenger (n = 24) heart rates were recorded during a calm and a rough HSC transit to assess workload, and also during an exhaustive running test to establish maximal heart rate (HRmax). Both transits followed the same course and travelled at an average speed of 40 knots for about 3 hours. Coxswains provided a sea-state description using the Beaufort scale. The UK Ministry of Defence Research Ethics Committee approved the protocol; subjects gave their written informed consent. RESULTS: Calm transit: sea-state 0 (flat-calm); heart rates: coxswain 45 % HRmax; passengers 34 %HRmax. Rough transit: sea-state 3-4; heart rates: coxswain 69 %HRmax; passengers 47 %HRmax. CONCLUSIONS: The elevated coxswain heart rates support the notion that driving a small HSC is a physically demanding task. Therefore, research should be focused on ways to decrease coxswain physical workload, by addressing the manner in which the craft has to be driven and decreasing the number and magnitude of repeated shocks.