Richard morris

Richard Morris

An Investigation Into Core Body Temperature Related To Water Saturation Of A Wetsuit And Its Influence On Hypothermia Incidence Within Asymptomatic Young Adult Subjects Richard Morris 1 Railway Cottages Falmouth Cornwall TR11 4BW ucasrichard@hotmail.co.uk

Abstract It has been recorded that warming of a wetsuit before cold water emersion is a behavioral thermoregulatory response undertaken to alleviate thermal stress. This experiment used 7 asymptomatic subjects between the ages of 18 and 28 to investigate whether the pre warming of a wetsuit has a negative impact on the bodies thermoregulatory processes and internal heat generation. The results showed that all seven subjects entered into mild hypothermia during the warmed wetsuit experiment where only four did during the cold wetsuit experiment. The mean cold water temperature for all seven subjects was 35.6˚C and the mean warm water temperature for all seven subjects was 34.9˚C. These results highlight that the warm water wetsuit experiment influenced an overall lower Tac showing that the warming of a wetsuit before cold exposure has a negative effect on thermoregulatory responses and internal heat generation. This present study pays particular attention to youths because their body surface area to mass ratio means they are more susceptible to environmental temperature.

Keywords Thermoregulation, Hypothermia, Body Mass, Vasodilatation, Vasoconstriction, Body temperature is regulated through the balance between heat accumulation and its dissipation. The body temperature of humans is usually regulated within a very narrow range (35˚C-40˚C), (Taylor et al 2004) in which physiological function is optimal (Tipton, et al. 2004). Research by Armstrong (2000) has shown that the body has various adaptive responses to changes in surrounding temperature, controlled by the existence of temperature sensors at several levels in the skin, which enable the body to sense heat flow and produce regulatory actions when heated and cooled (Webb 1995).

Cooling of core body temperature and hypothermia could be apparent in any situation that diminishes the ability to generate or conserve thermal energy leading to thermoregulatory insufficiency (Taylor et al 2004). The clinical definition of hypothermia is a Core Temperature (Tco) of 35 ºC (Steinman and Giesbrecht 2001) selected by The British Medical Association (British Medical Association BMA 1964).

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Richard Morris Golden and Tipton (2002) categorized two different types of hypothermia, acute and chronic. Diagnoses of hypothermia falls upon three classifications arbitrarily divided into Mild (35° - 32°C, Moderate (32° - 28°C) and severe hypothermia (> 28°C) (Francis 1998).

Immersion into cold water is one of the fastest ways to influence a change in cutaneous tone and can result in “cold water shock” (Tipton et al 1990). It is the result of a dramatic change in temperature causing the cold receptors in the skin to initiate powerful cardiovascular and respiratory responses (Taylor 2004) including an involuntary gasp, (Tipton et al 1990) hyperventilation, vasoconstriction of the skin (peripheral) blood vessels over most of the body, (Golden and Tipton 2002), sudden rise in heart rate, mean arterial blood pressure, cardiac output and stroke volume with a consequent reduction in cardiac frequency (Taylor et al 2004). Prolonged immersion would result in shivering thermogenesis (Taylor 2004), intensified by enhanced peripheral sensor activity as Skin Temperature (Tsk) declines, and further increased when heat loss exceeds thermogenesis (Taylor 204). Prolonged thermogenesis will result in metabolic fatigue (Shender 1995) and due to the absence of internal heat generation Tco will continue to fall.

Water, unlike air, provides practically no insulation at the skin-water interface (Golden and Tipton 2002) thus heat reaching the skin surface is rapidly transferred to the water and therefore the skin temperature becomes relatively close to the water temperature (Nadal 1984).

One of the most common ways of providing thermal insulation in cold water is the use of a wetsuit. Recent research by Polak and Edmund 2005 explain how the fabric layers of a wetsuit absorb significant quantities of water, and drying a wetsuit after use is a frustrating and inconvenient process. It commonly takes up to eight hours or longer for the external fabric layer to dry completely. The act of putting on a wet wetsuit can significantly deplete positive mental attitude especially if the individual does not normally wear a wetsuit. It has been recorded that one way of stopping the discomfort of putting on a wet wetsuit is to put the wetsuit on in a warm shower, or drench the wetsuit in warm water (say perhaps from a flask) (Eatock, pers.coms.). This inevitably makes the wetsuit more comfortable to put on and makes the individual warm, rather than cold. This is a clear sign of behavioural thermoregulatory responses to cold (Bowens, pers.coms).

Behavioural thermoregulatory responses are conscious activities undertaken to alleviate thermal stress (Golden and Tipton 2002).

Environmental heat stress increases the requirements for sweating and circulatory responses to remove body heat (Armstrong 2000). When the body is heated the brain causes the smooth muscles in your skin blood vessels to relax, allowing dilation and increased blood flow to the skin while the brain diverts blood away from inner organs. A common area where wetsuit warming is believed to be happening is at watersports centers (Whittle, pers.coms) where the prominent participant is children. The body surface area to mass ratio can have a significant influence on the body cooling rate (Taylor et al 2004) thus because children have a smaller skin surface area to adults, lower body fat (Taylor, et al, 2004) and low metabolic heat production due to their small muscle mass, their Tsk and Tco changes more rapidly.

This is only partly counteracted by an increased vasoconstriction in children reflected by a lower skin temperature (Inoue et al 1996) which appears to be related to age rather 2

Richard Morris than body size. Although beneficial in offsetting falls in core temperature, this increased vasoconstriction could make them susceptible to local peripheral tissue damage. (Nimmo 2004).

Wind chill is one of the most contributory factors in the etiology of cold injury (Golden and Tipton 2002) and is probably the main factor that would influence a rapid drop in a youths Tco taking part in watersports. This is because generally speaking these participants are not going to be subject to long immersion times in cold water. Relative air movement disturbs the boundary layer of air (forced convection) around the body and increases heat loss (Golden and Tipton 2002). Wind chill can directly result in non freezing cold injury (NFCI) even if the subject is clothed or covered by the wind. evaporative heat loss, which is enhanced by forced convection, will further extract heat from the surface of the clothing, thereby increasing the thermal gradient across it (Golden and Tipton 2002).

Whilst cold water immersion and thermoregulatory responses to the cold is widely researched, the physiological effect of heightened Tsk and Tco in youths before cold water immersion is yet to be thoroughly explored. The purpose of this present study was to investigate and compare the physiological effects of wind chill over a 20 minute basis for the subjects wearing a cold wet wetsuit and a warmed wet wetsuit to conclude whether a warmed wetsuit has a negative effect on thermoregulatory processes and internal heat generation. The author hypothesized the following: (1) that a warmed wet wetsuit would influence a noticeably faster drop in Tco, and (2) that the mean Tco for all of the subjects would be lower whilst wearing a warm wet wetsuit.

Methods Equipment list 2 Polar – S410 heart rate monitors, IRT 4020 ExacTemp Ear Thermometer, Alarm Hand Held Thermometer (Range: -50 ºC to +150 ºC or -58ºF to +302ºF, Resolution: 0.1ºC for 19.9ºC ~ +199.9ºC, Accuracy: ±1ºC in the range -30ºC ~ +150ºC,otherwise ±2ºC) Stop Watch, 12 inch Desk Fan (Size H48, W34.7, D25cm), Sitting Bench, Electrical Shower 40 ˚C ± 2 ˚C, Mini Thermo Anemometer – EA3010 (mph, Km/h,m/s or knots), Water Tub/Bath 11˚C ± 2 ˚C, Seven 5mm Neoprene Wetsuits, Results Tables.

Subjects Seven healthy Asymptomatic Male Subjects between the ages of 18 and 28 years were recruited from the university population. The subjects were screened using a professional medical form created by Cornwall College. They were then informed of all the experiment procedures and the associated risks and discomforts before providing written consent for their participation.

Location An indoor environment with a room temperature of 23 ˚C ± 2 ˚C. The location had access to an electrical shower with minimal distance between the shower and experiment area.

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Richard Morris The location had appropriate flooring that was suitable for a wet experiment to reduce the risk of slipping. In this experiment the location had stone flooring. Experiment area was in a suitable position to ensure water was kept away from electrical appliances and sockets.

Set up The subject was sat in a position where wind can be directly applied to the subjects face and core. In this case a sitting bench made of wood to reduce the risk of electrical conductivity and slipping was used with the fan position at the end of the bench. Subjects straddled the sitting bench with the Electrical Fan positioned exactly 1 meter from the Subject. The Fan was elevated and directed towards the subjects head and chest.

Control protocol Before the experiment basic anthropometric measurements were obtained including age, height, body mass, resting heart rate and tympanic temperature (˚C). Body fatness using skin fold measurements was also calculated using the Jackson and Pollack Method (1978). Resistance to heat flow provided by body fat (McArdle et al 1994) will affect an individuals response to the cold and in the years following the Pugh and Edholm (1955) report other investigators confirmed and quantified the finding that the decrease in body core temperature during water immersion was inversely related to the thickness of the subcutaneous fat layer. For this reason only subjects that have a body fat percentage between 10%BFP and 20%BFP will be used for the experiment. This ensures that the data gathered will not be greatly influenced by extreme body fat percentages; however this range still leaves enough room to comment on the amount of body fat in relation to the Subjects Insulated Auditory Canal Temperature (Tac).

Peripheral vasoconstriction has an indirect detrimental affect on the body and accelerates dehydration due to the relative increase of central blood volume. This inhibits the secretion of the AVP hormone (Armstrong 2000) which is responsible for the amount of water absorbed in the kidney, resulting in a higher urine volume and indirectly influencing dehydration. Therefore before the experiment all subjects will be required to drink at least 2 pints of water on the day of the experiment to minimize the chances of dehydration presenting itself in the data.

Alcohol has a direct affect on the thermoregulatory processes within the body and can increase the chances of cold injury in a number of ways. Alcohol stimulates skin blood vessel dilation, inhibits sensations of cold and pain, inhibits shivering directly preventing adequate heat production (Armstrong 2000) increases urine production thus influences dehydration and is commonly associated with poor judgment and co-ordination. It is for these reasons that all of the subjects will be asked to refrain from the consumption of alcohol for at least 24hours before the experiment begun. This was to ensure that the data gathered was not influenced by the effects of alcohol consumption.

An electrical shower with a set temperature of 40 ˚C ± 2 ˚C was used to ensure no variables in the water temperature. Water bucket containing water 11˚C ± 2 ˚C was used to soak wetsuits replicating sea water. This temperature is purposefully similar to the “Mean Sea Temperature in 1993 for Newlyn, Cornwall at 50° 6’ N, 5° 32’ W which was 4

Richard Morris 11.5°C (52.7 degrees Fahrenheit) with a monthly mean range from 8.6°C to 15.3°C” (Joyce 2006). This is too replicate the temperature of sea water as accurately as possible.

This temperature was checked and if necessary altered every 25 minutes to maintain a constant temperature. Only wetsuits that were made of a neoprene material and had a thickness of 5mm were used. All wetsuits had double sided liquid seems and barrier system to stop water entering the suit through the zipper. All wetsuits had a thermospan lining in the torso and G lock wrist and ankle seals.

Ethics – The Ethics of this experiment were all approved by Cornwall College and reviewed against the Hillsinky Agreement.

Safety risk assessment A detailed risk assessment was carried out prior to the experiment accounting for all factors including, subjects health and welfare, location and water temperature. (See appendices). This risk assessment is the same standard format used by Cornwall College and provided adequate safety risks to be recorded and measured.

Measures Heart rate was measured by the Polar – S410 heart rate monitors and the Auditory Canal Temperature (Tac) (˚C) was taken by an ExacTemp Ear Thermometer both recorded into results tables. Water temperatures °C and room temperatures °C were measured by the Alarm hand held water thermometer.

Experiment protocol The experimental trial consisted over one day with two sessions, one in the morning and the other in the afternoon. The morning session (Session 1) involved the subjects donning a wet cold wetsuit and sitting in front of a fan simulating wind chill for 20 minutes. The heart rate and Tac (˚C) of the subjects was taken at set intervals throughout the experiment. The afternoon session (Session 2) involved the subjects putting on a wetsuit in a warm shower then sitting in front of a fan simulating wind chill for 20 minutes.

Again, the heart rate and Tac (˚C) of the subjects was taken at set intervals throughout the experiment.

Both sessions took place in the chosen location with a room temperature of 23 ˚C ± 2 ˚C. The water tub/bath was filled with water that was 11˚C ± 2 ˚C. This was checked every 25 minutes and if necessary altered to maintain a constant temperature. This was checked throughout the day along with measuring the room temperature to ensure the environment remained the same. The Electrical Shower was set to a temperature of 40˚C ± 2 ˚C and was located a short walk to the experimental area. The Sitting bench had an electrical fan situated at the end facing the subject. The Fan was elevated so it was inline with the subjects head and directed towards to the subjects face and chest.

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Richard Morris Session 1 – Morning session On arrival the subject was asked to relax for 10 minutes in the room where the experiment was taking place. The subject then had their Resting Heart Rate taken and recorded. The subject then had their Tac (˚C) taken and recorded.

The subject’s wetsuit was soaked in the water tub/bath in 11˚C ± 2 ˚C water for 10 minutes. During this time the subject was equipped with the Polar – S410 heart rate monitor.

The subject, wearing board shorts then donned the wet wetsuit and sat on the bench facing the fan which was exactly 1 meter away from the subjects face. The heart rate and Tac (˚C) was again recorded and noted down as starting heart rate and temperature. As soon as these measurements were recorded the fan was turned on and put on the highest setting measuring 7 mph on the anemometer and the timer began. The subject remained seated in front of the fan for 20 minutes. Every 30 seconds the Tac (˚C) was recorded and every minute the heart rate was recorded.

This was repeated for all of the 7 subjects that participated in the experiment.

Session 2 – Afternoon session On arrival the subjects were again asked to relax for 10 minutes in the room where the experiment was taking place. The subject then had their Resting Heart Rate taken and recorded. The subject then had their Tac (˚C) taken and recorded.

The subject then donned the Polar – S410 heart rate monitor. The subject will then enter the shower with a temperature of 40˚C ± 2 ˚C measured by the Alarm Hand Held Thermometer. The subject will be in the shower for 7 minutes again wearing board shorts. After the 3rd Minute the Subject will put on the wetsuit in the shower and leave the shower once the 7 minutes is up. The subject must ensure that there head is wet, there entire body is exposed to the running water and there wetsuit is completely drenched in warm water.

After the shower the subject immediately sat on the bench facing the fan which was exactly 1 meter away from the subjects face. Again, the heart rate and Tac (˚C) was again recorded and noted down as starting heart rate and temperature. As soon as these measurements were recorded the fan was turned on and put on the highest setting measuring 7 mph on the anemometer and the timer began. The subject remained seated in front of the fan for 20 minutes. Every 30 seconds the Tac (˚C) was recorded and every minute the heart rate was recorded.

This was repeated for all of the 7 subjects that participated in the experiment.

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Richard Morris Results Subject 1 – Age: 22 Body Fat Percentage: 20% Resting Heart Rate (bpm-1):60bpm-1 Resting Auditory Canal Temperature: 37˚C Fig. 1 Auditory canal temperatures (Tac) for subject 1 during the warm and cold water wetsuit experiments. *Mean cold water wetsuit Tac: 35.1˚C * Mean warm water wetsuit Tac: 34.8˚C

Fig. 2 Heart Rate (bpm-1) for subject 1 during the warm and cold water wetsuit experiments. *Mean cold water wetsuit Heart Rate: 64 (bpm-1) * Mean warm water wetsuit Heart Rate: 66 (bpm-1)

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Richard Morris The cold and warm water wetsuit experiment was able to successfully lower Tco in subject 1. During the cold experiment the subject experienced a fall in Tco to 34.6˚C from their normothermic resting value of 37˚C. In the warm water wetsuit experiment the subject experienced an over lower decline in temperature with the lowest recording of 34.2˚C. Fig.1 marks a significantly faster fall in Tac during the warm water experiment and Tac declines from 36.1 to 34.2˚C in 4.5 minutes. This was a while degree colder than the temperature recorded at 4.5 minutes for the cold water wetsuit experiment. The mean cold water wetsuit Tas was recorded as 35.1˚C and the mean warm water wetsuit Tac was recorded as 34.8˚C. This shows a marked fluctuation betweent he hot and cold experiment and the subjects overall Tac was lower during the warm water wetsuit experiment.

The cold and warm water wetsuit experiment also successfully influenced a rise and fall in Heart Rate.

During the cold water experiment the subject experienced a rise in Heart Rate to 78(bpm-1) from their resting heart rate of 60 (bpm-1). This Heart Rate fell steadily for 4 minutes where it eventually reached the subjects resting heart rate levels. The Heart Rate fluctuated between 60-66bpm-1 for the rest of the experiment with a sudden fall in the last minute with a Heart Rate of 48(bpm-1). During the warm water experiment the Heart Rate did not fluctuated as much as the cold water experiment. There was a small rise in Heart Rate to 66(bpm-1) above the subjects resting heart rate levels. There was a further rise at 8.00 minutes, and again at 14.00 minutes where their Heart Rate increased to 72 (Bpm-1) but then fell again to 66 (bpm-1) where it stayed for the rest of the experiment. The mean cold water wetsuit Heart Rate was calculated at 64 (bpm-1) and the mean warm water wetsuit Heart Rate was calculated at 66 (bpm-1).

Subject 2 – Age: 18 Body Fat Percentage: 12% Resting Heart Rate (bpm-1):66 bpm-1 Resting Auditory Canal Temperature: 37.1˚C

Fig. 3 Auditory canal temperatures (Tac) for subject 2 during the warm and cold water wetsuit experiments. *Mean cold water wetsuit Tac: 35.2˚C * Mean warm water wetsuit Tac: 34.6˚C

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Fig. 4 Heart Rate (bpm-1) for subject 1 during the warm and cold water wetsuit experiments. *Mean cold water wetsuit Heart Rate: 72 (bpm-1) * Mean warm water wetsuit Heart Rate: 63 (bpm-1)

The cold and warm water wetsuit experiment was able to successfully lower Tco in subject 2. During the cold experiment the subject experienced a fall in Tco to 34.7˚C from their normothermic resting value of 37.1˚C. In the warm water wetsuit experiment the subject experienced an over lower decline in temperature with the lowest recording of 34.1˚C. Fig.3 marks a significantly faster fall in Tac during the warm water experiment and Tac declines from 36.1 to 34.1˚C in 5.0 minutes. This was 1.1˚C lower than the temperature recorded at 5 minutes for the cold water wetsuit experiment. The mean cold water wetsuit Tas was recorded as 35.2˚C and the mean warm water wetsuit Tac was recorded as 34.6˚C. This shows another marked fluctuation between the hot and cold experiment and the subjects overall Tac was lower during the warm water wetsuit experiment.

Again the cold and warm water experiment influenced a rise and fall in Heart Rate. During the cold water experiment the subject experienced a rise in Heart Rate to 90(bpm-1) from their resting heart rate of 66 (bpm-1). This Heart Rate fell dramatically from 90(bpm-1) to 72(bpm-1) in the first minutes. Then by the 4th minute the heart rate had again risen to 84(bpm-1). After the 9th minute the heart rate fluctuated between 66-72(bpm-1).During the warm water experiment the Heart Rate did not fluctuated as much as the cold water experiment but there was a still dramatic drop in Heart Rate from 78(bpm-1) to 60 (bpm-1) in the first minutes. The Heart Rate remained at 60(bpm-1) for 7.5 minutes when there was a small rise in Heart Rate to 72(bpm-1). The Heart Rate then fluctuated between 60-66(bpm-1) with another rise to 72(bpm-1) in the 17th Minutes. The Heart Rate then remained 66(bpm-1). The mean cold water wetsuit Heart Rate was calculated at: 72 (bpm-1) and the mean warm water wetsuit Heart Rate was calculated at 63 (bpm-1)

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Richard Morris Subject 3 – Age: 20 Body Fat Percentage: 11% Resting Heart Rate (bpm-1):66 bpm-1 Resting Auditory Canal Temperature: 38.1˚C

Fig. 5 Auditory canal temperatures (Tac) for subject 3 during the warm and cold water wetsuit experiments. *Mean cold water wetsuit Tac: 35.0˚C * Mean warm water wetsuit Tac: 34.6˚C

Fig. 6 Heart Rate (bpm-1) for subject 1 during the warm and cold water wetsuit experiments. *Mean cold water wetsuit Heart Rate: 65 (bpm-1) * Mean warm water wetsuit Heart Rate: 72 (bpm-1)

The cold and warm water wetsuit experiment was able to successfully lower Tco in subject 3. During the cold experiment the subject experienced a fall in Tco to 34.3˚C from their normothermic resting value of 38.1˚C. In the warm water wetsuit experiment the subject experienced an over lower decline in temperature with the lowest recording of 34.1˚C. Fig.5 marks a significantly faster fall in Tac during the 10

Richard Morris warm water experiment and Tac declines from 36.3 to 34.4 ˚C in 4.0 minutes. This is again a 1.1˚C lower temperature than the temperature recorded at 4 minutes for the cold water wetsuit experiment. The mean cold water wetsuit Tas was recorded as 35.0˚C and the mean warm water wetsuit Tac was recorded as 34.6˚C. This shows another marked fluctuation between the hot and cold experiment and the subjects overall Tac was lower during the warm water wetsuit experiment.

Again the cold and warm water experiment influenced a rise and fall in Heart Rate. During the cold water experiment the subject experienced a rise in Heart Rate to 84(bpm-1) from their resting heart rate of 66 (bpm-1). This Heart Rate fell rather sharply from 84(bpm-1) to 60(bpm-1) within the first 3 minutes. The Heart Rate remained at 66(bpm-1) for most of the experiment with again random rises to 72(bpm-1) at 6 minutes and 18 minutes. During the warm water experiment the subjects heart rate rose to 102bpm-1 and steadily declined to 66(bpm-1) by the 3 minute. It then fluctuated between 66(bpm-1) and 78(bpm-1) until the 11th minute where it found a rhythm fluctuating between 72(bpm-1) and 66(bpm-1) for the rest of the experiment. The mean cold water wetsuit Heart Rate was calculated at: 65 (bpm-1) and the mean warm water wetsuit Heart Rate was calculated at 72 (bpm-1) Subject 4 – Age: 18 Body Fat Percentage: 17% Resting Heart Rate (bpm-1):67 bpm-1 Resting Auditory Canal Temperature: 37.7˚C Fig. 7 Auditory canal temperatures (Tac) for subject 3 during the warm and cold water wetsuit experiments. *Mean cold water wetsuit Tac: 36.3˚C * Mean warm water wetsuit Tac: 35.6˚C

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Fig. 8 Heart Rate (bpm-1) for subject 1 during the warm and cold water wetsuit experiments. *Mean cold water wetsuit Heart Rate: 70 (bpm-1) * Mean warm water wetsuit Heart Rate: 68 (bpm-1)

The cold and warm water wetsuit experiment was able to successfully lower Tco in subject 4. During the cold experiment the subject experienced a fall in Tco to 35.7˚C from their normothermic resting value of 37.7˚C. In the warm water wetsuit experiment the subject experienced an over lower decline in temperature with the lowest recording of 35˚C. Fig.7 marks a significantly faster fall in Tac during the warm water experiment and Tac declines from 36.7 to 35.3˚C in 6.0 minutes. This was 1˚C lower than that temperature recorded at 6 minutes during the cold water wetsuit experiment. The mean cold water wetsuit Tas was recorded as 36.3˚C and the mean warm water wetsuit Tac was recorded as 35.6˚C. This shows another marked fluctuation between the hot and cold experiment and the subjects overall Tac was lower during the warm water wetsuit experiment.

Again the cold and warm water experiment influenced a rise and fall in Heart Rate. During the cold water experiment the subject experienced a rise in Heart Rate to 86(bpm-1) from their resting heart rate of 67 (bpm-1). This Heart Rate fell from 86(bpm-1) to 60(bpm-1) over the next 6 minutes with random fluctuation to 78(bpm-1) at 1 minute and 5 minutes. For the Rest of the experiment the Heart Rate then fluctuated between 72-66(bpm-1) with a random fall to 60(bpm-1) in the 11th minute. During the warm water wetsuit experiment the subjects heart rate rose dramatically to 102(bpm-1) where it fell to 78(bpm1) by the 1st minute. The Heart Rate fluctuated between 60(bpm-1) and 72(bpm-1) for the rest of the experiment until the 17th minute where it found a constant rhythm of 66(bpm-1) for the rest of the experiment.The mean cold water wetsuit Heart Rate was calculated at: 70 (bpm-1) and the mean warm water wetsuit Heart Rate was calculated at 68 (bpm-1)

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Subject 5 – Age: 19 Body Fat Percentage: 15% Resting Heart Rate (bpm-1):70 bpm-1 Resting Auditory Canal Temperature: 38˚C Fig. 9 Auditory canal temperatures (Tac) for subject 3 during the warm and cold water wetsuit experiments. *Mean cold water wetsuit Tac: 35.6˚C * Mean warm water wetsuit Tac: 34.8˚C

Fig. 10 Heart Rate (bpm1) for subject 1 during the warm and cold water wetsuit experiments. *Mean cold water wetsuit Heart Rate: 71 (bpm-1) * Mean warm water wetsuit Heart Rate: 78 (bpm-1)

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The cold and warm water wetsuit experiment was able to successfully lower Tco in subject 5. During the cold experiment the subject experienced a fall in Tco to 35.1˚C from their normothermic resting value of 38˚C. In the warm water wetsuit experiment the subject experienced an over lower decline in temperature with the lowest recording of 34˚C, the lowest recorded Tac of the entire experiment. Fig.9 marks an extremely faster fall in Tac during the warm water experiment and Tac declines from 36.4 to 34.8˚C in 4.5 minutes. This was 1.5˚C lower than that temperature recorded at 4.5 minutes during the cold water wetsuit experiment. The mean cold water wetsuit Tas was recorded as 35.6˚C and the mean warm water wetsuit Tac was recorded as 34.8˚C. This shows another marked fluctuation between the hot and cold experiment and the subjects overall Tac was lower during the warm water wetsuit experiment.

Again the cold and warm water experiment influenced a rise and fall in Heart Rate. During the cold water experiment the subject experienced a rise in Heart Rate to 78(bpm-1) from their resting heart rate of 70 (bpm-1). This Heart Rate fell from 78(bpm-1) to 72(bpm-1) over the next minute. For a few minutes the Heart Rate fluctuated between 66(bpm-1) to 78(bpm-1) where it eventually found a resting rhythm of 72(bpm-1). Again this experiment showed random falls in Heart Rate to 66(bpm-1). During the cold water wetsuit experiment the subjects Heart Rate increased greatly to 120(bpm-1). This was the highest Heart Rate recorded on the day. This had fallen to 90(bpm-1) by the 1st minute and 72(bpm-1) by the second minute. The Heart Rate fluctuated between 78-72(bmp-1) until the 8th minute where it rose to 84(bpm-1) for 2 minutes. The Heart Rate again fluctuated between 78-72(bmp-1) until the 16th minute where it dropped to 66 (bpm-1) and again continued to fluctuate between 78-72(bmp-1) for the rest of the experiment. The mean cold water wetsuit Heart Rate was calculated at: 71 (bpm-1) and the mean warm water wetsuit Heart Rate was calculated at 78 (bpm-1)

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Richard Morris Subject 6 – Age: 18 Body Fat Percentage: 10% Resting Heart Rate (bpm-1):60 bpm-1 Resting Auditory Canal Temperature: 37˚C Fig. 11 Auditory canal temperatures (Tac) for subject 3 during the warm and cold water wetsuit experiments. *Mean cold water wetsuit Tac: 36.1˚C * Mean warm water wetsuit Tac: 35.2˚C

Fig. 12 Heart Rate (bpm1) for subject 1 during the warm and cold water wetsuit experiments. *Mean cold water wetsuit Heart Rate: 61 (bpm-1) * Mean warm water wetsuit Heart Rate: 62 (bpm-1)

The cold and warm water wetsuit experiment was able to successfully lower Tco in subject 6. During the cold experiment the subject experienced a fall in Tco to 35.7˚C from their normothermic resting value of 37˚C. In the warm water wetsuit experiment the subject experienced an over lower decline in temperature 15

Richard Morris with the lowest recording of 34.1˚C. Fig.11 marks a clear difference between the temperature levels during the cold water experiment and the warm water experiment. There is a significantly faster fall in Tac during the warm water experiment and Tac declines from 36.5 to 34.9˚C in 3.5 minutes. This was again 1.5˚C lower than that temperature recorded at 3.5 minutes during the cold water wetsuit experiment. The mean cold water wetsuit Tas was recorded as 36.1˚C and the mean warm water wetsuit Tac was recorded as 34.2˚C. This shows another marked fluctuation between the hot and cold experiment and the subjects overall Tac was lower during the warm water wetsuit experiment.

Again the cold and warm water experiment influenced a rise and fall in Heart Rate. During the cold water experiment this particular subject encountered only a very slight rise in Heart Rate from their resting heart rate of 60 (bpm-1). Their Heart Rate rose to 66(bpm-1) in the 2 minute for 3 minutes, then reduced to their resting heart rate level of 60 for the rest of the experiment. During the warm water experiment the Heart Rate rose to 78(bpm-1) and fell steadily over 6 minutes to the subjects resting Heart Rate levels of 60(bpm-1) where it remained for the rest of the experiment. The mean cold water wetsuit Heart Rate was calculated at 61 (bpm-1) and the mean warm water wetsuit Heart Rate was calculated at 62 (bpm-1).

Subject 7 – Age: 28 Body Fat Percentage: 18% Resting Heart Rate (bpm-1):60 bpm-1 Resting Auditory Canal Temperature: 37˚C Fig. 13 Auditory canal temperatures (Tac) for subject 3 during the warm and cold water wetsuit experiments. *Mean cold water wetsuit Tac: 36˚C * Mean warm water wetsuit Tac: 34.8˚C

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Fig. 14 Heart Rate (bpm1) for subject 1 during the warm and cold water wetsuit experiments. *Mean cold water wetsuit Heart Rate: 63 (bpm-1) * Mean warm water wetsuit Heart Rate: 64 (bpm-1)

The cold and warm water wetsuit experiment was able to successfully lower Tco in subject 7. During the cold experiment the subject experienced a fall in Tco to 35.1˚C from their normothermic resting value of 37˚C. In the warm water wetsuit experiment the subject experienced an over lower decline in temperature with the lowest recording of 34.3˚C. Fig.13 marks a clear distinction between the temperature levels during the cold water experiment and the warm water experiment. There is a significantly faster fall in Tac during the warm water experiment and Tac declines from 35.7˚C to 34.3˚C in 2.5 minutes. This was a huge 2.1˚C lower than that temperature recorded at 3.5 minutes during the cold water wetsuit experiment. The mean cold water wetsuit Tas was recorded as 36˚C and the mean warm water wetsuit Tac was recorded as 34.8˚C. This shows another marked fluctuation between the hot and cold experiment and the subjects overall Tac was lower during the warm water wetsuit experiment.

Again the cold and warm water experiment influenced a rise and fall in Heart Rate. During the cold water experiment this particular subject encountered only a very slight rise in Heart Rate from their resting heart rate of 60 (bpm-1). Their Heart Rate rose to 66(bpm-1) in the 4th and apart from a fall to 60(bpm-1) at 6 minutes remained constant at 66(bmp-1) until the 12th minute. It then continued to fluctuate between 72(bpm-1) and 60(bpm-1) mainly staying at a constant rhythm of (60bpm-1). During the warm water experiment the Heart Rate rose again only very slightly to 66(bpm-1) and fell to 60(bpm-1) at 1 minute. It then remained ay 60(bpm-1) for most of the experiment with random fluctuations of 66(bpm-1) over the entire experiment. There was a noticeable rise of Heart Rate at 16 minutes where it rose to (72bpm-1) for 3 minutes before returning to 66(bpm-1) for the remainder of the experiment. The mean cold water wetsuit Heart Rate was calculated at 63 (bpm-1) and the mean warm water wetsuit Heart Rate was calculated at 64 (bpm-1).

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Richard Morris Fig. 15 Mean Auditory canal temperatures (Tac) for all 7 subjects during the warm and cold water wetsuit experiments.

The experiment successfully raised and lower the Tac of all subjects. There was also noticeable rises and falls in Heart Rate. Fig.15 shows the mean Tac Temperatures for all of the subjects over the 20 minute session for the cold and warm water wetsuit experiment. It is clear that the temperatures for the warm water wetsuit experiment are significantly lower than the temperatures for the cold water experiment. Throughout the entire session every mean temperature of the cold water wetsuit experiment has a value than that of the warm water wetsuit experiment. The lowest mean temperature for the cold water wetsuit experiment was 35.1˚C whilst the lowest mean temperature for the warm water wetsuit experiment was a distinctly lower 34.7˚C. The mean cold water temperature for all seven subjects was 35.6˚C and the mean warm water temperature for all seven subjects was 34.9˚C. Again these results highlight that the warm water wetsuit experiment influenced an overall lower Tac showing that the warming of a wetsuit before cold exposure has a negative effect on thermoregulatory responses and internal heat generation.

Discussion The primary finding of this present study was that pre-warming of a wetsuit before cold exposure has a negative impact on the bodies thermoregulatory responses to cold and internal heat generation. All of the subjects experienced at least a 1˚C lower overall Tac during the warm water wetsuit experiment. The most extreme of these being a whole 2.1˚C lower Tac during the warm water experiment.

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Richard Morris By providing a simulated chill it was possible to simulate an outdoor environment that would influence a fall in Tco. Golden and Tipton’s (2002) research concluded that wind chill is a major contributory factor in the etiology of cold injury. Relative air movement disturbs the boundary layer of air (forced convection) around the body and increases heat loss. Therefore because children taking part in water sports are not normally subject to long emersion times, a simulated wind chill was used to create a cold exposure rather than using a water bath and prolonged emersion times. This was also deemed ethically unsafe and controlling the safety measures of this experiment would be difficult within the facilities that were available.

Temperature was measured using an ExacTemp Ear Thermometer measuring the Auditory Canal Temperature (Tac). Traditionally, body temperatures are measured on the skin and in the rectum; thus, for easy comparison with much of the previous literature (Webb 1995). Due to the nature of the experiment it was decided to be taken in the Auditory Canal because it was easily accessible and control measures could be taken to ensure accurate results. Due to the subjects wearing wetsuits the only skin available would be on the extremities. It was decided that this would not give an accurate result of the mean Tsk. The extremities, particularly the hands, feet and ears, contain specialized networks of arteriovenous anastomoses that supply blood to the venous plexus directly from small arteries. These anastomoses play an important role in temperature regulation since their synchronous closing is linked to heat balance (Taylor et al 2004). Thus because vasoconstriction is not uniform over the entire body (Nimmo 2004) the extremities are more susceptible to the cold which if measured would give a significantly lower Tsk, and therefore, are not a reliable indicator of core body temperature (Chamberlain and Terndrup 1994).All of the subjects noted that their feet and hands were cold which is due to a shut down of peripheral perfusion reducing the cold venous return to the core reducing the heat loss from the limbs and extremities (Health and Safety Executive 1996). For children taking part in water sports this could prove to be a disabling factor further increased by the addition of a warm wetsuit before cold exposure.

Vasodilatation would cause peripheral blood to flow to the surface of the skin so as to produce heat loss. Sudden cooling of the hands and feet could inhibit feeling and dexterity (Golden and Tipton 2002) in the hands and feet making it had for children to function properly in the water, inevitably causing a serious health and safety risk.

The other option was measure the Tco in the rectum. However, for the same reason it was decided against as it would not be easily accessible if there was a problem voiding the results. Rectal thermometers would have given a accurate reading of Tco however it is mainly used for experiments over a long period such as 24h or more because it is the only measurement that subjects tolerate for long periods (Webb1995). Rectal temperature also lag behind core body temperature and the experiment was not long enough to record temperature changes.

For these reasons it was decided that the Tac accurate and suitable data for the. Research

by Chamberlain and Terndrup (1994) relieves many benefits to measuring the Tac. Ear Temperatures accurately reflect core body temperature, since the eardrum shares blood supply with the temperature control centre in the brain, the hypothalamus. It’s for this 19

Richard Morris reason that changes in the body are reflected sooner and more accurately in the ear than at other sites. This explains how some of the subjects experienced a dramatic change in temperature over a short period of time.

The data collected reveal many negative effects from the pre warming of a wesuit before cold exposure. The clinical definition of hypothermia is a Tco of 35°C or lower (Steinman and Giesbrecht 2001). 4 out of the subjects did not enter into clinical mild hypothermia in the cold water wetsuit experiment however during the warm water wetsuit experiment all of the 7 subjects entered into mild hypothermia (Tc = 32-35° C) (Steinman A, Giesbrecht G. 2001). Considering that the body temperature of humans is usually regulated within a very narrow range (35˚C-40˚C), (Taylor et al 2004) in which physiological function is optimal (Tipton, et al. 2004), the present study has proven that all subjects were exposed to extreme cold stress factors. Whilst this data shows that the subjects were in the stages of mild hypothermia research by Webb (1995) suggest that the recorded temperatures may not be entirely accurate to Tco. His research states how Auditory Canal Temperature is affected by cooling of the head (Webb 1995). The position of the simulated wind was aimed directly at the head and core of the subject meaning that head cooling is a strong possibility. Conflicting research by Taylor (2004) conflicts Webb’s (1995) research in stating that the head displays only a minimal constrictor response to cold, having a high sympathetic tone even under thermoneautral conditions, and is not involved in generalized peripheral vasoconstriction.

It is interesting to note that subject 1 had an initial greater fall in Tac during the warm water wetsuit experiment, however their Tac resolved to around the same temperature for both experiments. This was the only subject to maintain a similar temperature during both experiments and there mean temperature difference was only 0.3˚C. This subject had a boy fat percentage of 20% which was the highest out of all the subjects. This data clearly shows the correlation between mean weighted skin temperature and metabolic rate after exposure to cold air illustrating the high insulating capacity that fat confers (Nimmo 2004). Subject 4 who had a Body Fat Percentage of 17% supports this with a mean temperature during the warm water wetsuit experiment of 35.6˚C well above the average of 34.9˚C. The subjects with the lowest body fat percentages also showed the lowest temperatures most notably subject 5 with a Body Fat Percentage of just 11% who’s lowest recorded temperature was 34˚C, a whole degree below clinical threshold for mild hypothermia.

This present study was conducted on young adult males between the ages of 18-28. The author is particularly interested in the effects that pre warming of a wetsuit could have a child. Due to their high surface area to mass ratio (Taylor et al 2004) children are more susceptible to cooling and also warm environments. The results show that there is a steeper decline in Tas whilst wearing a warmed wetsuit and overall lower body temperature. When putting a wetsuit on in a warm shower you are exposing your skin to an intense heat environment and then trapping the warm water between the skin and the suit is creating an effective thermal layer. Due to the small body surface area to mass ratio this insulative layer will warm their Tsk and Tc relatively quickly however when immersed in cold water there will be a dramatic change in environmental temperature 20

Richard Morris initiating cold receptors in the skin. The results of this data suggest that by warming the Tsk and Tco before cold water immersion imposes a negative effect on your bodies thermoregulatory process meaning that entering into the stages of mild hypothermia earlier is a possibility. This poses great threat to children taking part in water sports as recorded symptoms of mild hypothermia include ataxia, dysarthria, apathy and even amnesia (Steinman and Giesbrecht 2001). Other symptoms include confusion and disorientation (Taylor et al 2004) and introversion, slowing of mental and physical activity, impairment of physical activity and errors of commission or omission (Golden and Tipton 2002). Due to their affected state hypothermic individuals are a risk to themselves and others (Golden and Tipton 2002). Due to these reasons it is clear that children taken part in watersports activities such as Sailing, Windsurfing, Coasteering and Kayaking increase there chances of injury through warming a wetsuit before emersion into water.

The data also collected the Heart Rate of subjects throughout both experiments. The results supported previous literature in that powerful cardiovascular responses are initiated (Taylor 2004) through cold water immersion. Subjects had a higher overall heart rate for the first few minutes of the cold water wetsuit experiments. Vasoconstriction increases the resistance to blood flow in the skin and increases flow returning to the heart in the veins because of hydrostatic squeeze (Golden and Tipton 2002). As the heart tries to pump against the peripheral resistance there is a simultaneous and sudden rise in heart rate, mean arterial blood pressure, cardiac output and stroke volume with a consequent reduction in cardiac frequency (Taylor et al 2004) thus the heart works harder as it tries to pump blood against the raised peripheral resistance (Golden and Tipton 2002). This would explain the higher mean Heart Rate during the first few minutes of the cold water wetsuit experiment.

The data concluded that putting a wetsuit on a shower increases the Heart Rate significantly due to a lot of muscles being recruited. This means more oxygen needs to be supplied to the muscles meaning the heart has to work harder in order to meet the demand for oxygen. The author believes that raised Heart Rate levels before cold water immersion could influence a further induced and more pronounced tachycardia. Whilst most children are not susceptible to external effects of Heart Disease elevated levels in Heart Rate through putting on a wetsuit in a shower could potentially have an impact on Cardiac Output and in extreme cases Cardiac Arrest.

Conclusion The author hypothesized the following: (1) that a warmed wet wetsuit would influence a noticeably faster drop in Tco, and (2) that the mean Tco for all of the subjects would be lower whilst wearing a warm wet wetsuit. This present study has concluded that the warming of a wetsuit before emersion into cold water is detrimental to the body’s thermoregulatory responses to the cold and internal heat generation. During the warm water wetsuit experiment all seven of the subjects entered into the stages of Mild Hypothermia between a Tac of about 35° and 32°C (Francis, 1998). The mean overall Tac was lower during the warm water wetsuit experiment and was calculated at 34.8°C and 21

Richard Morris the mean overall Tac for the cold water wetsuit experiment was 36째C. This concludes that by warming your wetsuit before being subject to cold exposure or cold emersion you actually decrease your body temperature and increase the chances of entering the stages of hypothermia sooner.

It is the authors strong belief that any water sports provider needs to ensure that no participant taking part in water sports warms there wetsuit before putting it on. This is especially important for children as their body surface area to mass ratio makes them especially susceptible to changes in environmental temperature.

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Bristow. K. G, Giesbrecht. G. G. 1988. Contribution of exercise and shivering to Recovery from induced Hypothermia (31.2째C) in One Subject. Faculties of Medicine and Physical Education and Recreational Studies, university of Manitoba, Winnipeg, Manitoba, Canada. Aerospace Medical Association, Washington, DC. Bowens. S, pers.com. Conversation on 30/11/10. Thermoregulatory Behaviour relating to not wanting to put on a wet wetsuit.

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4th edition. Auerbach P, editor. C.V. Mosby, St. Louis, 2001 Tikuisis P, (1989) Predicition of the thermoregulatory response for clothed immersion in cold water. Defence and Civil Insititute of Environmental Medicine. European Journal of Applied Physiology.

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