Exercise in the Cold
Assessing responses to exercise in the cold is no mean feat. There are supreme difficulties in recreating extreme conditions due to ethical constraints. Because of this, research tends to begin gently and develop over time, with one experiment taking place involving 'x' minutes of exercise at 'y' intensity in 'z' degrees Celsius. In so doing, subsequent researchers can show that this level is safe so they can push the time, workload and temperature just a little further. The alternative is for researchers to become involved in planned expeditions, or observe cold-weather sports participants or military personnel on training expeditions. With this approach there is less control of conditions and activities, but perhaps a finding more directly transferable to real-world scenarios.
Mental Performance in Cold Environments
It is fairly well accepted that extremes of temperature have a negative impact on both physical and mental performance. What is perhaps surprising, if not entirely alarming, is just what qualifies as 'extreme'. In 2002, a group of researchers (Pilcher et al., 2002) conducted a meta-analysis of the various high-quality, scientific studies that had been undertaken on mental performance in extremes of temperature. They found that the worst cognitive performance occurred at anything below 10oC and anything above 32.2oC. In the U.K., we would tend to regard 10oC as mild for winter, and 32.2oC as a good day to telephone work sick and head to Brighton beach. We would tend not to consider these temperatures as sufficient to affect the mental faculties.
The extent to which temperature affects performance in a cognitive test depends very much on the nature of the task. Cold exposure below 18.3oC results in a substantial negative affect on reasoning, learning and memory tasks. Conversely, attentional, perceptual and mathematical tasks, along with reaction times, tended to decline more with increasing heat than with cold (Pilcher et al., 2002).
Variations in the level of protective clothing, combined with sleep deprivation, wind-chill, and much lower ambient temperatures, would need to be assessed to give a fuller indication of the real consequences of cold exposure. However, based on these findings, navigation, discipline to eat, drink and rest, and self-awareness to recognise when it is time to wrap up a bit warmer, or else to climb into a sleeping bag or get a fire going, all require reasoning skills.
Learning and memory are, amongst other things, key to knowing where items of equipment are kept, how to use them, and what sort of survival skills need to be employed in a particular situation. It is fair to say that the mental faculties would be ticking over at their slowest rate when cold-weather racers, for example, are at their coldest, and when those faculties are needed the most.
Importantly, people involved in long-term exposure seem to manage better than those given a single, short blast of cold for an hour or two. This suggests a level of cold adaptation, whereby an individual's cognitive performance improves during the course of exposure. So, for those preparing to face the cold, it would appear that as we become more accustomed to the environment, so our ability to cope mentally should improve as well.
One issue that confounds many researchers of adaptations to the cold, particularly when investigating populations indigenous to higher latitudes, is that there really is not very much adaptation to investigate. This is mostly thanks to behavioural changes. In other words, if one ventures to visit sub-Arctic or Arctic populaces, what one invariably finds are people dressed up in very warm clothing.
In extremes of latitudes the cars are still heated, homes and offices are heated, and people are very experienced in how to protect themselves from the cold. If one takes a basking Brighton beach-dweller, clad in shorts, socks and sandals, and we drop them into the northern reaches of Scandinavia, even the most mentally sluggish of vocational truants will realise pretty swiftly that a warm refuge, pending an overhaul of their personal attire, is the order of the day.
In terms of the science, there seems to be little to be gained from getting people standing naked in a cold room to see what happens, because it is so unlikely that anybody ever finds themselves naked and standing about in the cold for long in real life. Hence, there is a concern that science is unlikely to be discovering very much of real use. But then, how does a researcher decide what level of protective clothing is appropriate, and what sort of weather conditions their subjects should be tested in? It makes investigation a fairly challenging task, if one desires that the findings of a study actually be applied in some way.
One researcher (Mäkinen, 2007), found that circumpolar people did not demonstrate any sort of acclimatisation to cold, and that this was most probably due to how they wore adequate protective clothing, enjoyed high temperatures in their homes, and only permitted themselves the briefest of exposures to the outside world. What that researcher (Mäkinen, 2007) did find, however, was that cold affected cognitive performance, by increasing levels of distraction and vigilance.
Whilst distraction is a negative consequence, increased vigilance could be either positive or negative, depending on the circumstances. Distraction and increased vigilance could be negative if it means a racer's pace is slowed whilst the gears of the mind are whirring away on anything else. Conversely, increased vigilance might be useful if directed at awareness of the land and signs of danger, such as avalanche risk, hazardous ground conditions, and advancing bears.
One particularly interesting finding of that study (Mäkinen, 2007), was that simple tasks suffered the most, whereas more complex tasks could actually improve in mild or moderate cold conditions. Mild and moderate cold are relative terms, of course, as they depend upon both external conditions and the effectiveness of clothing and so on. Whether or not setting up a bivvy or getting a fire going is simple or complex, is probably a matter of training and experience, amongst other things. Irritatingly, although some signs of habituation to the cold have been reported following repeated exposures (Makinen, 2007), these did not have any positive effect on the signs of cognitive performance that were being measured.
Relationship between Psychological & Physiological Effects
Two men participating in a Greenland expedition were monitored and assessed for changes in physiological, psychological and behavioural data (Bishop et al., 2001). Although behaviour was fairly consistent, due to the nature of the expedition, it was found that physiological and psychological functioning were very closely related, and followed the degree of challenge of the activity. Changes were evaluated both through levels of stress-related hormones and psychological assessments. The more they suffered physically, the more that caused them to suffer psychologically, and vice versa.
The physiological and psychological effects of repeated cold exposures have also been assessed in night-shift workers (Ozaki et al., 2001). The researchers found that circadian variations led to a marked decrease in core temperature at night, compared with during the day. This occurs regardless of levels of physical activity. In other words, a set amount of physical activity during the night will result in a rise in core temperature that is much lower than the same level of activity during the day (Ozakiet al., 2001).
Conversely, the investigators reported that skin temperature was actually higher during the night, despite a cooler core temperature, and suggested that this may have been due to circulatory (thermoregulatory) inefficiencies. It was also noted that manual performance decreased at night, and that this must have reflected an overall cooling of the body. The main conclusion of the study was that night workers are more susceptible to hypothermia when exposed to cold at night, than day workers going about their duties in the day, even for the same environmental temperatures. This is predominantly due to the natural variations in circadian rhythms (Ozakiet al., 2001).
This finding also has direct relevance to endurance athletes who are racing during the night, as they will be more susceptible to the cold then, even if maintaining the same exercise intensity as during the day. However, it is most likely that exercise intensity will actually decrease at night, due to motivational factors, increased perceptions of fatigue, or simply greater care being required to prevent an accident whilst walking or running. Any such drop in intensity will occur when the core temperature is already predisposed to being lower, and when in fact environmental temperatures will most likely be lower than during the day. Thus, a number of factors converge to increase the risks when exercising in the cold at night.