Moving in extreme environments: open water swimming in cold and warm water

Abstract

Open water swimming (OWS), either ‘wild’ such as river swimming or competitive, is a fast growing pastime as well as a part of events such as triathlons. Little evidence is available on which to base high and low water temperature limits. Also, due to factors such as acclimatisation, which disassociates thermal sensation and comfort from thermal state, individuals cannot be left to monitor their own physical condition during swims. Deaths have occurred during OWS; these have been due to not only thermal responses but also cardiac problems. This paper, which is part of a series on ‘Moving in Extreme Environments’, briefly reviews current understanding in pertinent topics associated with OWS. Guidelines are presented for the organisation of open water events to minimise risk, and it is concluded that more information on the responses to immersion in cold and warm water, the causes of the individual variation in these responses and the precursors to the cardiac events that appear to be the primary cause of death in OWS events will help make this enjoyable sport even safer.

Cold Stress Effects on Exposure Tolerance and Exercise Performance

“…One swimmer completed the crossing of Lake Windermere (16.5 miles) in just under 6 h with an end-swim rectal temperature of 36.1 • C, whereas the other swimmer, who was swimming the race the next day, got out voluntarily after 3 h with a rectal temperature of 36.8 • C. The swimmer who trained in a heated pool swam for 130 min, became incapacitated, and his deep body temperature was 35.3 • C. Conversely, the apparent absence of cold habituation in other published accounts (16,73,118) may explain why some swimmers failed to complete the required distance because of hypothermia, despite relatively high water temperatures (18)(19) • C) and short swim times (less than 3 h) (16,73). Recent work (19,237) also seems to confirm Golden et al's hypothesis that outdoor swimmers demonstrate a form of "insulative" adaptation when swimming in cold water (better able to defend deep body temperature) but a "hypothermic" adaptation (low metabolism, increased comfort, and rapid fall in deep body temperature) when sitting still in cold water. The role of BAT and nonshivering thermogenesis in the insulative response has not been assessed in this group.…”

“…Indeed, some swimmers appear to be able to "swim to unconsciousness" probably because they are able to exercise at such high intensities that they end up mixing the superficial and deep tissue/body temperatures. Thus the limbs and deep body cool at about the same rate and unconsciousness occurs (30-33 • C) before impaired muscle function (28 • C) (237). The ability of these swimmers to withstand prolonged immersion in cold water without apparent ill-effect was attributed to their unique combination of physical fitness and substantial thickness of subcutaneous fat (191).…”

Hypothesised mechanisms of swimming-related death: a systematic review

“…These suggestions are designed to minimise the need for breath holding, chance of aspirating water into the nares, and the potential for crowding, anger and anxiety 29. These include limiting the size of the starting group, or using well-spaced ‘waves’, in which a smaller number of swimmers starts at a time, and the intervals between starting groups is adequate.…”

“…Self-selection of starting waves by swimmers based on their actual or perceived ability may also minimise the anxiety or chaos of mass start events. Encouraging swimmers with known swim-related anxiety or panic, to seek assistance to minimise this anxiety before participating again in a mass-start swim event may increase safety 29. Further, allowing for the athletes to preswim before the start in order to better acclimatise to the water temperature may minimise the cold-water response.…”

Accidental hypothermia in recreational activities in the mountains: A narrative review

“…This is not intended as a comprehensive review of all outdoor activities or organized sport. Hypothermia due to submersion or immersion in water during water‐based activities has not been reviewed and can be found elsewhere …”