Human beings are warm-blooded and depend on maintaining a relatively stable temperature to function and support life; temperature fluctuations beyond the normal range cause a variety of physiological responses. For the most part we have little or no control over these biological responses, but two effects are paramount. As cooling begins at the body’s surface and extremities, muscle and nerve functions become impaired. If it comes on suddenly, or progresses beyond the extremities, panic can inhibit the mind’s ability to reason clearly. Panic isn’t the result of thinking or evaluating the situation, it’s the brain’s signal that there is no time to think. We have little control over these responses except, perhaps, for our ability to make better decisions if we are familiar and practiced with the situations under which they occur.
Anyone who has been out in the cold long enough to begin shivering or feel their fingers and toes gradually stiffen is familiar with these basic functions, and most of us are aware that prolonged exposure to extreme cold can lead to hypothermia. Boaters usually understand that if their boat overturns and they’re in the water for hours, they’re in danger of hypothermia. But rowers don’t expect to be in the water for hours.
What makes rowing on cold water especially dangerous is not only that water cools the body much faster than air, but a particular set of responses to sudden immersion in cold water.
Four Phases of Cold Water Immersion
As characterized by USRowing, the four phases of sudden immersion in cold water are 1) Cold Shock; 2) Swimming Failure; 3) Hypothermia; and 4) Post rescue collapse. Any one of them can be fatal and rowers have died as a result.
Among these four concerns, cold shock and cold incapacitation should be of greatest concern to scholastic boaters. Fatalities among rowers have been rare, but those related to cold water almost certainly could have been prevented by PFDs.
Cold shock can be fatal within the first moments of immersion. Cold incapacitation (swimming failure) may occur within minutes after immersion or it can set in gradually over a half hour or more. Hypothermia generally progresses gradually after an hour or more has passed before becoming fatal. Post rescue collapse, resulting from a collapse of arterial blood pressure, may kill at the point of rescue or several hours afterward. Although water temperatures in the 60’s and 70’s may cause these effects, the colder the water the more dangerous it is and USRowing considers temperatures below 50F as extremely dangerous.
Cold Shock
Cold shock refers to the body’s involuntary response to sudden immersion in cold water. There is no specific temperature at which it occurs because biological effects are dependent on many factors such as body weight, mass, fat, and temperature. The colder the water temperature is, the greater the thermal shock and the greater the threat. Air temperatures appear to be irrelevant.
When cold shock occurs it causes an immediate, involuntary, gasping reflex.
If someone is thrown out of the boat by an ejector crab or a boat capsizes as the result of a fast moving squall or a collision with a motorboat, the gasping reflex occurs regardless of whether the rower’s head is above or below the water. If the gasp occurs under water and takes in cold water rather than air the situation is, obviously, extremely critical. Even if the head is above water, the cold shock will still limit the body’s ability to hold air and causes hyperventilation, which in turn causes decreased blood flow to the brain. If the hyperventilation cannot be brought under control quickly, it can lead to disorientation and unconsciousness.
Under these conditions, USRowing advises young rowers to “concentrate on staying afloat with your head out of water and once your breathing is more normal and your heart rate is reduced you will think more clearly…”
Cold Incapacitation and Swimming Failure
Thinking more clearly in this situation a rower suddenly thrown into the water might recall USRowing’s warning that “swimming failure sets in after three to thirty minutes.” If an eight capsizes in 40-degree water and the coaching launch only has one person on board or doesn’t have the capacity to rescue nine people, it’s important to understand what “swimming failure” means.
Today, experts refer to swimming failure as a consequence of “cold incapacitation,” or the impaired function of muscles and nerves as they cool. Most of us don’t think about the milliseconds it takes for nerve transmissions to jump synapses, or information to be transferred from sensory perception through the brain and to muscles (about 200 milliseconds), but milliseconds are important for coordination. The simple fact is that muscles and nerves function better when they’re warm and they’re impaired as they cool. It’s part of the reason for warming up before exercising, and part of the reason cold water is so dangerous.
Rowers should understand this: no matter how strong you are or how good a swimmer you are, cold water inhibits neuromuscular function.
Most rowing programs rely on launches being available if rowers capsize or get in trouble and USRowing’s safety video advises that “If the coaching launch is nearby, everyone should be thrown a lifejacket and put it on.” But in the time it takes for the launch to reach the boat, unpack the lifejackets and throw them to the rowers, rowers may begin to feel the effects of cold incapacitation. The colder the water the faster the effects will occur. By the time the launch arrives, some rowers may not be able to catch the PFDs, put them on, and buckle them, or they may have lost hold of the boat.
Because cold shock occurs immediately and cold incapacitation can occur within three to five minutes of a cold water accident, they are much greater threats to rowers than hypothermia.
Hypothermia
Hypothermia refers to the cooling of the body’s core temperature below the level at which it can maintain normal metabolic functions. Because water cools the body approximately 20-25 times faster than air, immersion in water colder than 25C (77F) can lead to hypothermia substantially faster than comparable air temperatures. Temperatures that might induce hypothermia over a course of many days in the air can be fatal within hours in water. If one or two eights overturn and all the crew are able to get back in the swamped boats or hold onto the overturned shells, hypothermia still can be life-threatening.
Post Rescue Collapse
Finally, it should be noted that even after an accident in which rowers survive the effects of cold shock, swimming failure, and hypothermia, the traumas of sudden cold water immersion can lead to a fatal collapse of arterial blood pressure even after rescue seems to have been successful, and even after hospitalization not all victims of hypothermia survive.
These are the facts. They’re the reason USRowing considers cold water “extremely dangerous.” It’s the reason an increasing number of coaches recommend PFDs on cold water and experienced rowers wear them. And if experienced rowers can wear them in sculls, inexperienced rowers can wear them in eights.
Statistically speaking, very few rowers have died from these effects, but, statistically speaking, very few people row under cold-water conditions.
The questions raised – particularly for scholastic rowers and their parents – are whether these risks are worth taking and whether they can be mitigated by the implementation of better standards, including the simple use of PFDs on cold water.
For more information links are provided to references and sources in the “Links” section.
© 2016 RowSafeUSA.Org