Includes abstract. / Includes bibliographical references. / Maximal oxygen consumption (VO2max) is typically defined by the presence of the "plateau phenomenon" during incremental exercise tests, in which O2 consumption levels-off in spite of increases in workload. This is thought to reflect a limitation in the capacity of the heart to pump O2 enriched blood to the exercising limbs. Some researchers however question not only the biological validity of the "plateau concept", based on mathematical and methodological issues, but whether O2 delivery to the exercising muscles indeed sets the upper limits for VO2max. This thesis aimed to address some of these controversies.

Includes bibliographical references. / In periods of prolonged stress and pain from strenuous exercise, the body produces chemicals called endorphins that help it endure pain. These natural analgesics are presumably only released when the level of pain intensity is at least moderately high. The PANIC/separation distress system is built on the same pathways as the physical pain system, and is responsible for the ‘mental pain’ (feelings of panic anxiety, loss and sorrow) that is associated with the loss of an attachment object, or separation from it. Given this overlap, it is reasonable to expect that endorphin release can affect depressive symptoms in a positive way. There is existing evidence that exercise has a beneficial effect on depressive symptoms, yet the underlying physiological mechanism has yet to be properly determined. The purpose of this three-armed prospective randomized control pilot study was therefore to try to establish this mechanism by investigating whether intensive exercise can improve the symptoms of moderate depression as a result of demonstrable increases in plasma &#946;-endorphins. It has previously been established that exercise-induced &#946;-endorphin release correlates positively with the intensity of the exercise. There were two central hypotheses for this study. The first was that the mechanism behind the improvements seen in depressive symptoms due to exercise is the same mechanism that is responsible for the established analgesic effect of exercise, namely endorphin release. The second hypothesis was that only high-intensity exercise (i.e. great that 70 of heart rate reserve) will be sufficient to produce a guaranteed endorphin release, whereas moderate-intensity exercise (just under 50% of the heart rate reserve) and very low intensive exercise would not be sufficient to release endorphins, and would therefore not result in an improvement in depressive symptoms. The main aim was therefore to investigate whether intensive exercise (greater than 70% of heart rate reserve) improves moderate depression, and if so, whether this correlates with a demonstrable increase in &#946;-endorphins. This study therefore wished to determine which of low, moderate or high intensity exercise alleviates the symptoms of depression. It also intended to determine whether an increase in &#946;-endorphins correlates to an improvement in the participants’ depression levels, and whether greater &#946;- endorphin release occurs during high-intensity exercise compared to low- and moderate intensity exercise. Male participants (n = 33) with moderate levels of depression were randomly assigned to one of three experimental groups of varying exercise intensities: High-intensity (160 beats per min (bpm)), Moderate intensity ( 140bpm), and a low-intensity control group (under 120bpm). All participants underwent a six-week exercise program that involved participation for three days per week, for one hour per day (i.e.18 sessions in total). Once weekly, the Hamilton Rating Scale for Depression (HAM-D) and the Montgomery Åsberg Depression Rating Scale (MADRS) were administered to each participant. The participants in the High-and Moderate-intensity exercise groups each had 5ml of blood drawn, once per week, before and after exercise, in order to measure their &#946;-endorphin levels, and to track any changes in these levels over time. The participants in the Control group had blood samples taken twice – once at the start of the study (a baseline measure), before and after exercise, and once on completion of the study, before and after exercise. The results indicate that both Moderate- and High-intensity exercise improved the participants’ depression levels, while the Control group also showed some improvement, but not to the same extent as the other two groups. A significant difference (p = < 0.0001) was found when comparing the initial and final HAM-D scores between all three groups. The participants’ MADRS scores also improved between all three exercising groups. A significant difference (p = 0.0182) was found when comparing the initial scores within each of the three groups to their final MADRS scores. No significant difference was found in the serum &#946;- endorphin levels when comparing the Moderate- with the High-intensity group. The differences between the baseline and post-exercise serum &#946;-endorphin measurements were also not significantly different for both the Moderate- and High-intensity groups (p= 0.953 and p= 0.992 respectively), while the Control’s pre- to post levels decreased significantly (p < 0.017). A significant difference between the Control-, Moderate-, and High-intensity groups (p = <0.022) was found when comparing the three groups’ serum &#946;-endorphin concentrations after they engaged in exercise. Overall, the results of this pilot study go against the hypothesis that only High-intensity exercise would improve symptoms of moderate depression, as both high- and moderate-intensity exercise had a clear positive impact on depression scores. However, consistent with this hypothesis, very-low intensity exercise did not seem to have as beneficial an effect. The mechanism underlying the benefit of exercise on the symptoms of depression cannot be conclusively confirmed given the overall &#946;-endorphin results. A larger sample size and more accurate analysis methods of &#946;-endorphin levels are required in order to test these tentative findings more rigorously.

Profound changes occur within the female breast with increasing age; glandular atrophy, increased skin laxity and stretched Cooper‟s ligaments cause an inferior lateral migration of the breast tissue. However, the current lingerie market predominantly revolves around bras designed for younger women that older women may feel are inappropriate for their physique. Literature regarding age-appropriate clothing has postulated that bras should be designed based on specific shapes, populations and usages. Yet the bra preferences of older women have been neglected in the literature. By determining women's requirements, the performance of current bras may be ascertained, and subsequent alterations may be recommended for bra design in order to optimise bras for older women if required. The aims of the current thesis were to: provide a wider understanding of the bra requirements of women aged 45 to 65 years, determine the key bra performance variables for this population, develop procedures to assess these variables and to determine the current appropriateness of a small sample of bras for this population. To achieve the research aims the thesis contained five studies. The first study was exploratory in nature, using focus groups and interviews to develop a knowledge base on the bra preferences of women aged 45 to 65 years. A survey was subsequently designed and implemented to determine the key bra performance variables among a wider sample of the population. The results of these studies identify the general dimensions that women consider when purchasing a bra (comfort, support, aesthetics, practicalities, and psychological aspects). From these dimensions, 11 key bra performance variables that are of importance to older women were derived (comfort, support, bra's ability to stay in place, appearance under clothes, silhouette, breast shape, breast lift, shoulder straps, discreetness, fabric and fit). Methods to quantify the key bra performance variables were required to assess the performance of current bras for older women. The third experimental study developed methods which minimised the limitations of existing procedures, and determined the validity and reliability of these methods. As a result of this study, methods to assess the 11 key bra performance variables were deemed acceptable for both objective and subjective measures. In the fourth study, two bras were selected from a popular and unpopular brand; the performance of these bras was assessed with regard to the 11 key bra performance variables. The results indicate that women aged 45 to 65 years preferred a bra that minimises breast kinematics, provides greater breast projection and lifts the breast sufficiently. Although differences lay between the bare breasted and bra conditions, the two bras performed similarly despite the difference in popularity. The final study incorporated a four week wearer trial to elucidate any changes in performance that may appear with increased usage. Subjective ratings of breast support and the bras' ability to stay in place were lower following the wearer trial. The bras tested performed well for the bra variables; comfort, fit, support and shoulder strap position. However, the remaining key bra performance variables may require alteration to ensure their appropriateness for women aged 45 to 65 years. It is concluded that women aged 45 to 65 years are generally cognisant of changes to their breasts as they age, subsequently seeking bras that are different from those they previously would have worn. The findings of this thesis suggest that alterations in bra design are required to optimise bras for older women.

Personal cooling garnents (peGs) are designed to relieve thermal stress in occupations that require the use of personal protective clothing (e.g. fire fighter, military personnel). The cooling source in peGs is usually delivered continuously, which over long periods requires a large battery source. Intermittent cooling has been found to be as effective as continuous cooling at maintaining thermal balance. Based on the observation that larger improvements in thermal perceptions are associated with rapid changes in skin temperature, it was hypothesised that intermittent cooling could also enhance thennal perceptions (i.e. temperature sensation and thennal comfort). The overall aim of the studies presented in this thesis was to test this hypothesis. In order to detect differences between intermittent and continuous cooling on thermal perceptions, it was important to use a reliable measurement tool to assess perceptual responses in conditions where a PCG would be utilised. The first study described in this thesis assessed the reliability of a graphic visual analogue scale (VAS) against a Likert scale (LS) for validity and reproducibility in the measurement of thennal perceptions in non-uniform, dynamic thermal environments. The study involved three identical conditions in which thermal perceptions were measured by both the V AS and LS in response to changes in the torso microclimate. During the condition, participants walked (Skm.hr-] , 2% incline) in a warm environment (3S0C, SO% relative humidity [RH]) and wore clothing (I.2 clo) that covered 88% of the body. The torso microclimate was manipulated by ventilating air of different temperatures and relative humidity through an air-perfused vest (APV). These thermal conditions were similar across all the studies presented in this thesis. The V AS were found to be slightly more reproducible for local thermal perceptions than the LS , and had greater validity during both stable and non-uniform, dynamic thermal environments. Therefore the use of the graphic VAS was adopted in all subsequent studies. To develop the intermittent cooling profiles that were assessed for their ability to enhance thermal perceptions, the second study involved ventilating different air temperatures (-15- 26°C) through the APV to determine what type of flu ctuations in skin temperatures are required to enhance thermal perceptions. The results suggested that the rate of change in mean skin temperature (f'sk) and torso skin temperatures (T sktorso) had a greater influence on thermal perceptions than absolute changes in Tsk and T sktorso. The results also confirmed the results from the first study, that increasing evaporative heat loss at the skin surface was the most effective method to manipulate the rate of change of skin temperatures, and consequently, thermal perceptions. To compare the capability of intermittent and continuous cooling profiles to enhance thermal perceptions, whilst maintaining thermal balance, the final study involved ventilating the APV with either fluctuating or continuous air velocities during both exercise and rest Three different intermittent cooling profiles were used; sinusoidal, sawtooth and step-change. Upon completion of the experiment, participants stated their preferred cooling profile. Based on the results it was concluded that intermittent cooling, which had 50% less air flow than continuous, maintained both thermal balance and thennal comfort when compared to continuous cooling. Out of the intennittent cooling profiles, the sinusoidal profile produced significantly cooler sensations and was 4111 participants' preferred choice. The results suggest that the presence of a significantly higher torso relative humidity (RH1orso) in the intennittent cooling profiles, compared to continuous profile, may have confounded their capability to enhance thennal perceptions over time. In addition, the cooling profi le that was perceived to the 'coolest' and/or the most ' stable' was generally the participants' preferred choice. This suggests that large fluctuations in skin temperature are not always perceived favourably. Based on the studies conducted as part of this thesis, it is concluded that in order to minimise high levels of RHtorso and provide smoother transitions in temperature sensation, an optimal cooling profile should consist of: 1) a sinusoidal pattern with a frequency greater tban 0.000139 Hz, 2) have a ratio of 2:1 ON/OFF periods, 3) OFF periods no longer tban 3 minutes, 4) highest flow rate not to exceed 255 L.min-], 5) provide a rate of change in f sk and t sklOISO of -{).29°C.min-1 and O. 78°C.min-], respectively, and 6) the incorporation of a drying agent into the design of an APV.

Many international and national standards exist for the testing and certification of immersion suits. Some require the thermal protective properties of immersion suits to be tested with human volunteers in calm, circulating 2°C water. The knowledge gap that currently exists between the benign testing conditions used in international standards and specifications, and the harsh environments that an immersed individual find themselves in following a marine accident, could result in unexpectedly poor levels of performance, with fatalities occurring sooner than expected following accidental immersion. Study 1 determined the heat loss from the skin of volunteers in immersion suits and immersed in wind and waves. Twelve healthy participants (Age: 25.8 [5.9] years old; Mass: 81.7 [13.1]kg; Height: 176.2 [7.7]cm) performed four, one hour immersions in the following conditions: Calm water; Wind-only; Waves-only; and Wind + Waves. Compared to Calm (67.21 [4.70]W·m-2), all the other immersion conditions produced a significantly greater increase in mean skin heat flow (MSHF) (Wind: 79.60 [6.70]W·m-2; Waves: 78.8 [4.52]W·m-2; Wind + Waves: 92.00 [8.39]W·m-2). The Wind + Waves condition produced a significantly greater increase in MSHF compared to all other conditions. Study 2 built upon the findings of the first by investigating the extent to which human thermal responses were related to the severity of weather conditions. Twelve healthy males (Age: 23.9 [3.3] years old; Mass: 83.2 [4.9]kg; Height: 181.0 [4.9]cm) performed three, three hour immersions in the following conditions: Calm water; Weather 1; and Weather 2. Compared to the calm water condition (62.96 [2.98]W·m-2], both weather conditions produced a significantly greater increase in MSHF (Weather 1: 76.75 [6.26]W·m-2; Weather 2: 79.53 [6.24]W·m-2). There were no significant differences in the change in gastro-intestinal temperature (TGI) across immersion conditions (Calm: -0.10 [0.31]°C; Weather 1: -0.29 [0.30]°C; Weather 2: -0.20 [0.28]°C]. There were no significant differences in V · O2 across immersion conditions (Calm: 0.325 [0.054]L·min-1; Weather 1: 0.332 [0.108]L·min-1; Weather 2: 0.365 [0.080]L·min-1). Study 3 investigated the effect of simulated water ingress under an immersion suit on human thermal responses during immersions in varying weather conditions. Twelve healthy males (Age: 25.6 [5.6] years old; Mass: 82.7 [10.2]kg; Height: 181.0 [4.7]cm) performed three, three hour immersions in the same conditions as Study 2, but with 500mL of water underneath the immersion suit. Compared to the calm water condition (79.45 [9.19]W·m-2), both weather conditions produced a significantly greater increase in MSHF (Weather 1: 102.06 [11.98]W·m-2; Weather 2: 107.48 [3.63]W·m-2). There were no significant differences in the change in TGI (Calm: -0.35 [0.14]°C; Weather 1: -0.38 [0.15]°C; Weather 2: 0.29 [0.25]°C) or V · O2 (Calm: 0.449 [0.054]L·min-1; Weather 1: 0.503 [0.051]L·min-1; Weather 2: 0.526 [0.120]L·min-1) across conditions. Survival times were calculated for the participants of Studies 2 and 3. There was no difference in the predicted survival times for the Study 2 participants for both the calm (> 36 hours) and wind and wave conditions (> 36 hours). The predicted survival times for the participants of Study 3 were significantly lower in the turbulent conditions (16 hours) compared to calm (27 hours). The predicted survival times of the participants in turbulent conditions were up to half those calculated for calm water immersions. The results collected in Studies 2 and 3 were used to calculate the change in total insulation in varying conditions compared to being dry. Immersions in wind and waves will reduce immersion suit insulation by 27%; 500mL of water leakage will reduce it by 24%; wind, waves and 500mL of water combined will reduce it by 43%. The predicted amount of oxygen consumption (V · O2 P) to produce the amount of heat required to remain in thermal balance can be estimated by rearranging the equations used to calculate metabolic heat production and insulation. If heat loss exceeds the assumed maximum heat production of 206W·m-2, hypothermia will eventually develop. The point at which heat loss exceeds maximum heat production has been determined in a range of conditions. It is concluded that: immersions in wind and waves causes a significant increase in heat flow from the body compared to calm conditions. Testing individuals and immersion suits in conditions not representative of the area where they are to be used may, or may not, result in an over-estimation of performance depending on the capacity of an individual’s thermoregulatory system.

Developing a scientific understanding of the breast support implications for the female recreational athlete will make a significant contribution to the breast biomechanics literature, provide valuable information to bra designers and help athletes make informed decisions about their breast support requirements. The work in this thesis determined the effect of a high and low breast support condition on biomechanical and perceptual variables during steady-state running, intermittent exercise and vertical jumping in a population of larger-breasted female recreational athletes. In order to assess breast kinematics an appropriate method of assessing bra fit was needed. Within this programme of research the use of best-fit criteria was first developed and then demonstrated that traditional bra fit methods overestimate band size (76% of participants) and underestimate cup size (84% of participants). During all activity modes a well-fitted high support bra significantly (p < 0.05) reduced breast kinematics and increased breast comfort. For steady-state running, alterations in lower-extremity biomechanics led to more distance being covered per minute (3.08 m; p = 0.006) and therefore a potential for improved performance when participants ran with high breast support. More acute knee flexion during sprinting (p = 0.008) and less sagittal plane thorax range of motion (p < 0.044) in the high breast support condition during the intermittent treadmill protocol could also benefit running performance. Increases in the range of motion of upper-extremity variables during treadmill activity were related to increases in some breast kinematic variables (r = 0.465 to 0.742); therefore certain individuals may require greater breast support than others. With increased breast kinematics there was a trend towards participants landing from vertical jumps with lower ground reaction forces coupled with increased thorax, thigh and knee flexion (r = 0.564 to 0.607). This suggests participants attempted to soften their landing, which may affect subsequent performance. Vertical jumping and sprinting elicited the highest magnitudes of vertical (0.08 m) and mediolateral (0.03 m) breast displacement respectively, questioning whether steady-state running is the most effective activity mode for testing bra efficacy. The reduction of anterioposterior breast kinematics should also be a consideration for bra design as they related most closely to breast comfort and biomechanical variables across all activity modes. Knowledge of the breast support implications for larger-breasted female recreational athletes was progressed in this thesis and bras offering high multi-planar support are promoted as they were found to be beneficial for performance within the activities investigated.

Water-based activities are often undertaken in cool water (15°C - 35°C), and can therefore result in thermal discomfort, which will affect the overall experience. In contrast with thermal comfort(TC) in air, very little research has been undertaken investigating TC in water. The studies presented in this thesis were designed to better understand the determinants of TC during and following immersion in cool water, at rest and during light physical activity.

Physiological adaptation to environmental stressors is often studied in isolation, but these stressors are frequently combined outside of laboratory settings, for example cold and hypoxia at altitude. There is also limited information about the effect that adaptation to one environment has on exposure to another. The five studies in this thesis were conducted in humans to assess the effect cold habituation has on the response to a simulated hypoxic exposure, and also to investigate a possible mechanism through which any change may occur. A possible site for the 'cross-adaptation' between cold habituation and hypoxia is the autonomic nervous system. Heart rate variability (HRV) is an non-invasive measurement technique which has been used to quantify autonomic activity. The two main frequency bands of interest when using HRV are referred to as the Low-Frequency (LF) band (the power found between 0.04 and 0.15 Hz) and the High-Frequency (HF) band (the power found between 0.15 and 0.4 Hz). Study One assessed the reliability of heart rate variability as a technique to indicate autonomic activity during both paced (breathing in time to a standard audible signal) and spontaneous breathing conditions, and at different cycling exercise intensities in a thermoneutral environment. It was hypothesised that within each condition HRV indices would be reliable between repeated recordings, which were separated by 96 hours. Eight participants performed each condition on the two occasions. Analysis of the data (coefficients of variation [CV] and intraclass correlation coefficients [ICC]) showed that the paced breathing condition was the most reliable condition, and time domain HRV indices were reliable, whilst not all frequency domain HRV indices were. Normalising and log transforming the raw data did improve reliability and log transformed total and high frequency (Ln HF) power and low:high frequency ratio (Ln LF:HF) met the a priori criteria (CV <10 % and ICC > r=0.8). It was concluded that most log transformed HRV indices were reliable at rest, during paced breathing and during moderate intensity exercise. Thus, the hypothesis was accepted, but caution was advised as several of the indices were close to exceeding the reliability criteria (Ln total power, Ln HF and Ln LF:HF) and a second autonomic measurement technique may be considered to substantiate its use. The previous study identified that Ln HF power increased when breathing frequency was reduced at rest. Study Two investigated the effect that alterations in breathing patterns had on HRV indices during rest and unloaded seated cycle ergometery (0 Watts) in 16 male participants. It was hypothesised that breathing which was externally paced would increase HF power compared to spontaneous breathing conditions. HF power was elevated during the paced breathing conditions in comparison to spontaneous breathing at rest and during unloaded exercise. Consequently, the hypothesis was accepted. Thus, ventilatory variables should be recorded in following studies as there may be links between ventilation and HRV indices. The previous studies used participants' freely chosen cadence when cycling, this may have influenced the HRV. The third study tested the hypothesis that cycling cadence affected HRV indices. HRV indices from 16 male participants were analysed when cycling at 40, 60, 80 and 100 revs.min-1 on an unloaded (0 Watts) and loaded (100 Watts) seated cycle ergometer. HRV indices declined as cadence was increased. Thus, the hypothesis was accepted. If HRV indices were to be calculated during subsequent experiments, both cadence and power output would have to be standardised. The first three studies provided information on the conditions which must be present to produce reliable HRV data during moderate intensity exercise. These studies also indicated that an additional means of measuring autonomic activity should be included. Study Four was designed to establish if one hypoxic exposure would influence a second exposure, if there was no effect the model could be adopted for the final experiment. This study also examined the effect of hypoxia on HRV indices at rest and during exercise. It was hypothesised that exercise and hypoxia would exert separate and additive effects on HRV indices and catecholamine concentrations. Twelve male participants rested and exercised on a loaded cycle ergometer (100 Watts) in normoxic (faction of inspired Oxygen, FIo2 0.2093) and hypoxic conditions (FIo2 0.15) on two occasions, separated by 96 hours. HRV and catecholamine concentrations were similar between the normoxic and hypoxic resting conditions. During exercise in normoxia catecholamine concentrations increased and Ln HF power was reduced, further increases in catecholamine concentrations and a reduction in Ln HF power were found during exercise in hypoxic conditions. The hypothesis was rejected for resting conditions, and accepted for the exercise conditions. It was also found that the first hypoxic exposure did not influence the HRV indices and catecholamine concentrations of the second hypoxic exposure and this model could therefore be used for the final experiment. The final study (Study Five) tested for the presence of a 'cross-adaptation' response in cold habituated humans to hypoxic exposures during rest and moderate intensity exercise. This study was designed on the basis of the information obtained from the previous four experiments and tested the hypothesis that cold habituation by repeated cold-water immersions would reduce the sympathetic activity and cardio-respiratory responses during loaded cycling (100 W) in hypoxic conditions (FIo2 0.12). Thirty-two male participants underwent six, five minute immersions in either cold (12 °C) or thermoneutral (35 °C) water over a three day period. The normoxic and hypoxic exposures were performed before and after the water immersions. It was established that cold habituation attenuated the sympathetic response to loaded exercise during an acute hypoxic exposure and reduced the number and severity of acute mountain sickness (AMS) symptoms. The study provides the first evidence of a cross-adaptation between cold habituation and hypoxic exposure in humans. This was not found in participants who performed thermoneutral water immersions. Therefore, the hypothesis was accepted. In conclusion, in four of four participants whose catecholamine concentrations were analysed and eight from 16 volunteers whose HRV was analysed, showed that cold habituation reduces the sympathetic response to an acute hypoxic stimulus during loaded cycling. However, it is not known if this cross-adaptation provides an adaptive or maladaptive response to prolonged exposure to hypoxia or altitude. Additionally, the permanence of the cross-adaptation also requires further investigation.

When exercise is undertaken in warm, humid conditions, the thermal gradient between the skin and environment, and the capacity for evaporative heat loss, are reduced. These factors, along with an increase in metabolic heat production, lower work capacity and exercise performance. Thermoreceptors located within the skin and deep in the body convey information on this accumulation of thermal energy to higher brain structures and, if mean body temperature rises uncontrollably, the cumulative neuronal input is thought to produce inhibitory signals that lower work capacity, such that metabolic heat production decreases to protect the organism from heat injury. Lessening these inhibitory signals may enhance or help to maintain exercise performance in the heat. The inhibitory signals might be lessened by cooling the skin and deep body temperature prior to or during exercise, or perhaps by applying menthol on the skin, or some combination of these. Menthol is a chemical compound that activates cold receptors (TRPM8) in the skin to elicit cool sensations. These receptors are not otherwise activated unless cooled below 27 °C. Hence, menthol, when applied to the skin of heat stressed humans, may provide a “cool’’ neuronal input to higher brain structures in addition to the neuronal signals arising from warm thermoreceptors located within the body. But menthol may also induce a heat storage (cold defense) response that would then heighten the activity of warm receptors deep in the body. Therefore, it is not clear whether menthol might reduce, enhance or help to maintain exercise performance in heat stressed humans. Moreover, no studies have assessed the perceptual and thermoregulatory response to menthol during rest or exercise, or the consequence of its repeated use. Before it is recommended as a possible ergogenic aid, these studies should be undertaken. The early work presented in this thesis tested the hypotheses that a water-based spray, containing ethanol and/or menthol, would enhance evaporative cooling when sprayed on the skin, thereby lowering heat storage and improving thermal perception compared to an unsprayed Control condition; but menthol would also improve thermal perception independent of temperature by directly stimulating cold receptors, during rest and exercise in warm, humid conditions. The hypothesis that menthol-mediated cool sensations would not undergo any habituation after repeated exposures was also tested. The general approach to testing these hypotheses involved presenting human participants with a thermal challenge that would induce warm sensations and increase thermal discomfort, whilst encouraging a level of heat storage that could be compensated for by increasing heat loss through v sodilation and sweating. This was achieved by manipulating metabolic heat production through a combination of rest and fixed intensity exercise in warm (30 °C) and humid (70 %) conditions. The influence of a menthol solution spray was tested against the backdrop of this thermal challenge. The results supported the general hypothesis that a water-based upper-body spray containing menthol can increase sensations of coolth compared to no spraying or wateronly spraying during rest and exercise in warm, humid conditions, but menthol also influences body temperature regulation. The effect that menthol exerts over perception and thermoregulation differs by dose and fades with time. Specifically, 0.2 % menthol spraying encourages heat storage by enhancing vasoconstriction, and there is no habituation in these responses. 0.05 % menthol spraying did not encourage any additional heat storage compared to a Control spray. Menthol also influenced perception, with a 0.2 % menthol spray promoting cooler sensations and greater irritation than 0.05 % menthol and Control spraying. Compared to a Control spray, 0.2 % menthol reduced thermal comfort during rest and improved it during exercise, while 0.05 % menthol did not alter thermal comfort during rest, and may have improved it during exercise. Neither menthol spray influenced perceived exertion during exercise. Menthol-mediated cool sensations lasted 15 to 30 minutes. Both 0.2 % and 0.05 % menthol sprays underwent an habituation compared to the Control spray, with cool sensations diminishing after repeated daily exposures. It is concluded that a 0.05 % menthol spray, which induces cool sensations without a significant heat storage response, could be considered as a perceptual cooling intervention with some capacity to enhance evaporative heat loss when sprayed on the skin during rest and moderate fixed-intensity exercise in the heat. A 0.2 % menthol spray might be deployed later in exercise, but may increase heat storage and irritation. Further testing is required to identify whether menthol spraying improves maximal exercise performance.

The studies presented in this thesis were conducted to develop two minimum fitness standards, one for the Maritime and Coastguard Agency and the second for the Oil and Gas Industry. This provided the opportunity to compare across the essential tasks and resultant standards. The following stages were used for both the Maritime and Coastguard Agency and Oil and Gas Industry: a. Review the tasks requiring a significant physical fitness component (Task Analysis); b. Determine the importance of the physically demanding tasks and identify those which are critical for success and safe work (Task Assessment); c. Establish the method of best practice (Technique) for undertaking the essential tasks; d. Establish and agree the minimum performance standard for the essential tasks (Task Performance) when performed using the method of best practice; e. Assess the physical and physiological demands of these tasks (Task Quantification); f. Design and validate a simple-to-administer minimum fitness standard. The essential tasks and fitness requirements of the Maritime and Coastguard Agency fell into three groups, these were: Group 1 (All Operations): achieve a maximum aerobic score of at least 31 mL.kg-¹.min-¹ based on the aerobic demand of 21.8 mL.kg-¹.min-¹ required to carry a stretcher at the head-end 200 m at a speed of 3.2 km.h-¹; continuously lift a 3 kg sledge hammer 10 times above shoulder height, based on hammering a stake into the ground; pull a rope, with a resistance of 35 kg, and maintain this load for 15 s based on manning a main rescue-line; carry a 19 kg hand-held load 200 m in 3 min 45 s allow 3 min 45 s rest, then carry a 25.5 kg hand held load, 200 m in 3 min 45 s, based on the ability to carry a stretcher (89 kg) as part of a four person team. Group 2 (Rope Technicians) should complete all the tasks as Group 1, plus pass all the technical competencies currently in place for Rope Technicians. Group 3 (Mud Technicians) as Group 1, plus achieve a predicted maximum aerobic score of at least 39 mL.kg- ¹.min-¹ based on the aerobic demand of 27.4 mL.kg-¹.min-¹ required to pull a stretcher across the mud at 0.8 km.h-¹, (this equates to covering 200 m in 15 minutes), prior to performing a simulated mud rescue. The essential tasks and the minimum fitness requirements of the Oil and Gas Industry were: Stair and Ladder-Climbing, achieve a predicted maximum aerobic score of at least 31 mL.kg-¹.min-¹ based on the aerobic demand of 23.4 mL.kg- ¹.min-¹ required to climb a flight of stairs at a rate of 80 steps.min-¹ and 23.6 mL.kg- ¹.min-¹ to climb a ladder at 24 rungs.min-¹; Manual Handling, based on the requirement to climb a flight of stairs at a rate of 80 steps.min-¹ for a minute carrying a load of 10 kg, 20 kg or 25 kg; Valve Turning, based on the requirement to continuously turn a medium size valve (25.4 cm diameter) set at a torque of 8.3 N.m, for 5 min; Emergency Response Team, achieve a predicted maximum aerobic score of at least 41 mL.kg-¹.min ¹, based on the aerobic demand of 30.7 mL.kg-¹.min-¹ required to pull a trailer/foam monitor at a speed of 5 km.h-¹. If trailer/foam monitors are not used achieve a predicted maximum aerobic score of at least 39 mL.kg-¹.min-¹ based on the aerobic demand of 28.9 mL.kg-¹.min-¹ required to climb a ladder at 34.5 rungs.min-¹. Stretcher carry 89 kg either in a two or four person lift (dependant on the facility), rope haul the heaviest anticipated load (10 kg first aid kit) up 10 m gantry, roll out a 23 m fire hose. There were no time constraints recommended for hauling kit and rolling out a hose. For those essential tasks that could not be assessed by a direct task measurement or a direct task simulation, a Predictive selection test was recommended and validated. Prediction intervals were used to take into account the inherent error between the predictive tests and the direct measurements, to determine “Pass”, “Borderline” and “Fail” categories. As a result of this work a modular approach was adopted in which individuals only undertake those test applicable to their job, with a combination of direct task measurements, direct task simulations, and Predictive selection tests recommended. It is suggested that, where possible, the use of a direct task measurement or simulation should either be progressive e.g. stretcher-carrying, or performed after a Predictive selection test, in order to reduce the risk of injury when the individuals proceed to undertake the direct task measurement or simulation e.g. manual handling. This approach has meant that consideration is given to the health and safety of the individuals undertaking the fitness standard whilst maintaining a high level of face validity.