Investigating manual performance when using push buttons following cold water hand immersion

The purpose of this study was to investigate manual performance of humans when using push buttons following cold water hand immersion. An experiment involving 29 human participants was carried out to measure the activation rate of twelve different shaped push buttons mounted on a novel test apparatus after their dominant hand was immersed in cold (2 °C) and thermoneutral (34 °C) water for 2 min. A series of standardized hand dexterity tests were completed to assess the participants' baseline tactile sensitivity in a dry thermoneutral state. The mean baseline performance of participants indicates that they were representative of the general population. The button test apparatus was developed specifically for this experiment and was comprised of 12 different buttons at different locations on the panel which were varying in size, surface shape and texture. After the participants immersed their dominant hand in the assigned temperature condition, their index finger was guided to the centre of the panel, and they were instructed to find and press as many buttons as they could in a 2-min time period using only their index finger. For the button panel test, the participants' view was obstructed from seeing the buttons. The results of the study indicate that temperature does not influence the activation rate of the push buttons on the button test apparatus. In addition, button size (large) was the most significant factor, followed by shape (protruding), however button texture was not a significant parameter. Given that exposure to cold water reduces manual performance, along with anecdotal evidence from survival training centres that users sometimes struggle to activate PLBs, the motivation for this research was to understand how humans interact with these devices in cold water emergency situations. It is expected that the results of this research will be useful for designers of emergency signalling devices used for rescue at sea.