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1.
J Physiol Sci ; 73(1): 26, 2023 Oct 17.
Article in English | MEDLINE | ID: mdl-37848829

ABSTRACT

Heat acclimation/acclimatisation (HA) mitigates heat-related decrements in physical capacity and heat-illness risk and is a widely advocated countermeasure for individuals operating in hot environments. The efficacy of HA is typically quantified by assessing the thermo-physiological responses to a standard heat acclimation state test (i.e. physiological biomarkers), but this can be logistically challenging, time consuming, and expensive. A valid molecular biomarker of HA would enable evaluation of the heat-adapted state through the sampling and assessment of a biological medium. This narrative review examines candidate molecular biomarkers of HA, highlighting the poor sensitivity and specificity of these candidates and identifying the current lack of a single 'standout' biomarker. It concludes by considering the potential of multivariable approaches that provide information about a range of physiological systems, identifying a number of challenges that must be overcome to develop a valid molecular biomarker of the heat-adapted state, and highlighting future research opportunities.


Subject(s)
Acclimatization , Hot Temperature , Humans , Acclimatization/physiology , Biomarkers , Phenotype , Heart Rate/physiology
2.
BMJ Mil Health ; 169(1): 94-101, 2023 Feb.
Article in English | MEDLINE | ID: mdl-32094215

ABSTRACT

Women can now serve in ground close combat (GCC) roles, where they may be required to operate alongside men in hot environments. However, relative to the average male soldier, female soldiers are less aerobically fit, with a smaller surface area (A D), lower mass (m) with higher body fat and a larger A D/m ratio. This increases cardiovascular strain, reduces heat exchange with the environment and causes a greater body temperature increase for a given heat storage, although a large A D/m ratio can be advantageous. Physical employment standards for GCC roles might lessen the magnitude of fitness and anthropometric differences, yet even when studies control for these factors, women sweat less than men at high work rates. Therefore, the average female soldier in a GCC role is likely to be at a degree of disadvantage in many hot environments and particularly during intense physical activity in hot-arid conditions, although heat acclimation may mitigate some of this effect. Any thermoregulatory disadvantage may be exacerbated during the mid-luteal phase of the menstrual cycle, although the data are equivocal. Likewise, sex differences in behavioural thermoregulation and cognition in the heat are not well understood. Interestingly, there is often lower reported heat illness incidence in women, although the extent to which this is influenced by behavioural factors or historic differences in role allocation is unclear. Indeed, much of the extant literature lacks ecological validity and more work is required to fully understand sex differences to exercise heat stress in a GCC context.


Subject(s)
Heat Stress Disorders , Military Personnel , Female , Humans , Male , Sex Characteristics , Exercise/physiology , Heat-Shock Response
3.
BMJ Mil Health ; 169(1): 37-45, 2023 Feb.
Article in English | MEDLINE | ID: mdl-35393357

ABSTRACT

BACKGROUND: This study evaluated cognitive workload in soldiers undertaking a long duration march wearing different loads. METHODS: Military participants (n=12 men and n=10 women) performed four 3-hour loaded marches (12.25 km at 4.9 km/hour) wearing either 21 kg, 26 kg, 33 kg or 43 kg. During the march, accuracy and response time were measured using the verbal working memory n-back test (0, 1, 2 and 3) and two bespoke Go/No Go tests (visual/auditory) to assess inhibition of a pre-potent response. RESULTS: The physical demands of the march increased with load and march duration but remained at moderate intensity. N-back test accuracy ranged from 74% to 98% in men and 62% to 98% in women. Reduced accuracy was observed as load and time increased. Accuracy during the visual Go/No Go test also reduced with load, accuracy ranged from 69% to 89% in men and 65% to 90% in women. No differences due to load or time were observed during completion of the auditory Go/No Go task; accuracy ranged from 93% to 97% in men and 77% to 95% in women. A number of participants were unable to complete the march due to discomfort. Reports of discomfort were more frequent in women, which may have contributed to the greater reductions in accuracy observed. CONCLUSION: These data provide further evidence that cognitive performance of military personnel can be affected during long duration loaded marching. Women reported discomfort from equipment more frequently than men, which may make them more susceptible to declines in cognitive performance. These findings highlight important considerations for equipment procurement.


Subject(s)
Military Personnel , Male , Humans , Female , Military Personnel/psychology , Walking/physiology , Weight-Bearing/physiology , Time Factors , Cognition/physiology
4.
Rhinology ; 59(5): 485-487, 2021 Oct 01.
Article in English | MEDLINE | ID: mdl-34428265

ABSTRACT

It has long been claimed that non-wetsuit cold water swimming (CWS) benefits health (1), and anecdotally cold-water swimmers claimed to suffer fewer and milder infections, though this was not directly measured. A boost to immunity is biologically plausible: stress hormones are released during cold-water immersion (2), and short-term stress may ready the immune system for injury or infection (3). However, very few studies have investigated immune system markers and/or actual illness in habitual cold-water swimmers.


Subject(s)
Respiratory Tract Infections , Swimming , Cold Temperature , Humans , Water
5.
Exp Physiol ; 106(2): 385-388, 2021 02.
Article in English | MEDLINE | ID: mdl-33174651

ABSTRACT

This short review was prompted by The Physiological Society's recent online symposium on variability. It does not deal with a specific methodology, but rather with the myth that certain environmentally-induced clinical conditions can be identified, quantified, simplified and monitored with a single methodology. Although this might be possible with some clinical conditions, others resist the prevailing reductionist approach of minimizing rather than exploring variation in pathogenesis and pathology, and will not be understood fully until the variation in cause and effect are embraced. This is likely to require comprehensive methodologies and collaboration.


Subject(s)
Adaptation, Physiological/physiology , Cold Injury/physiopathology , Vasoconstriction/physiology , Animals , Humans
7.
Exp Physiol ; 102(11): 1335-1355, 2017 11 01.
Article in English | MEDLINE | ID: mdl-28833689

ABSTRACT

NEW FINDINGS: What is the topic of this review? This is the first review to look across the broad field of 'cold water immersion' and to determine the threats and benefits associated with it as both a hazard and a treatment. What advances does it highlight? The level of evidence supporting each of the areas reviewed is assessed. Like other environmental constituents, such as pressure, heat and oxygen, cold water can be either good or bad, threat or treatment, depending on circumstance. Given the current increase in the popularly of open cold water swimming, it is timely to review the various human responses to cold water immersion (CWI) and consider the strength of the claims made for the effects of CWI. As a consequence, in this review we look at the history of CWI and examine CWI as a precursor to drowning, cardiac arrest and hypothermia. We also assess its role in prolonged survival underwater, extending exercise time in the heat and treating hyperthermic casualties. More recent uses, such as in the prevention of inflammation and treatment of inflammation-related conditions, are also considered. It is concluded that the evidence base for the different claims made for CWI are varied, and although in most instances there seems to be a credible rationale for the benefits or otherwise of CWI, in some instances the supporting data remain at the level of anecdotal speculation. Clear directions and requirements for future research are indicated by this review.


Subject(s)
Cold Temperature , Cryotherapy/methods , Hydrotherapy/methods , Immersion , Water , Adaptation, Physiological , Animals , Body Temperature Regulation , Cold Temperature/adverse effects , Cryotherapy/adverse effects , Cryotherapy/history , Cryotherapy/mortality , Drowning/mortality , Drowning/physiopathology , Exercise Tolerance , History, 18th Century , History, 19th Century , History, 20th Century , History, 21st Century , History, Ancient , Humans , Hydrotherapy/adverse effects , Hydrotherapy/history , Hydrotherapy/mortality , Immersion/adverse effects , Risk Assessment , Risk Factors , Swimming , Water/adverse effects
8.
J Therm Biol ; 58: 99-105, 2016 May.
Article in English | MEDLINE | ID: mdl-27157339

ABSTRACT

UNLABELLED: This study assessed whether donning a garment saturated with menthol and ethanol (M/E) can improve evaporative cooling and thermal perceptions versus water (W) or nothing (CON) during low intensity exercise and rest in warm, humid conditions often encountered in recreational/occupational settings. It was hypothesised there would be no difference in rectal (Tre) and skin (Tsk) temperature, infra-red thermal imagery of the chest/back, thermal comfort (TC) and rating of perceived exertion (RPE) between M/E, W and CON, but participants would feel cooler in M/E versus W or CON. METHODS: Six volunteers (mean [SD] 22 [4] years, 72.4 [7.4] kg and 173.6 [3.7] cm) completed (separate days) three, 60-min tests in 30°C, 70%rh, in a balanced order. After 15-min of seated rest participants donned a dry (CON) or 80mL soaked (M/E, W) long sleeve shirt appropriate to their intervention. They then undertook 30-min of low intensity stepping at a rate of 12steps/min on a 22.5cm box, followed by 15-min of seated rest. Measurements included heart rate (HR), Tre, Tsk (chest/back/forearm), thermal imaging (back/chest), thermal sensation (TS), TC and RPE. Data were reported every fifth minute as they changed from baseline and the area under the curves were compared by condition using one-way repeated measures ANOVA, with an alpha level of 0.05. RESULTS: Tre differed by condition, with the largest heat storage response observed in M/E (p<0.05). Skin temperature at the chest/back/forearm, and thermal imaging of the chest all differed by condition, with the greatest rate of heat loss observed in W and M/E respectively (p<0.01). Thermal sensation differed by condition, with the coolest sensations observed in M/E (p<0.001). No other differences were observed. CONCLUSIONS: Both M/E and W enhanced evaporative cooling compared CON, but M/E causes cooler sensations and a heat storage response, both of which are likely mediated by menthol.


Subject(s)
Body Temperature Regulation , Clothing , Ethanol/chemistry , Menthol/chemistry , Thermosensing , Adolescent , Adult , Body Temperature , Exercise , Hot Temperature , Humans , Humidity , Male , Perception , Rest , Skin Temperature , Thermography , Water/chemistry , Young Adult
9.
Exp Physiol ; 101(1): 1-14, 2016 Jan.
Article in English | MEDLINE | ID: mdl-26391095

ABSTRACT

Professor Sir George Lindor Brown (1903-1971) is known for his pioneering research into cholinergic neuromuscular transmission. However, during World War II he worked in hyperbaric physiology, and his research into underwater physiology greatly improved the safety of divers. It is perhaps fitting, therefore, that this review, which accompanies the Physiological Society's G. L. Brown Prize Lecture for 2015, explores the impact and mitigation of the environmental stresses which, to varying extents, have shaped our past, threaten our present and inform our future. From a whole-body, integrative perspective, this review examines our current understanding of microgravity, hypo- and hyperbaria, heat, cold air and cold water as both individual and combined stresses. Consideration is given to ways of mitigating the threat posed by environmental extremes, including the differing extents to which humans can demonstrate adaptation to them. Finally, recommendations for further study are suggested that might result in both direct and indirect insights.


Subject(s)
Adaptation, Physiological/physiology , Environment , Acclimatization , Animals , Humans , Stress, Physiological
10.
Scand J Med Sci Sports ; 26(8): 875-84, 2016 Aug.
Article in English | MEDLINE | ID: mdl-26220213

ABSTRACT

We examined the effect of short-term heat acclimation with permissive dehydration (STHADe) on heat acclimation (HA) and cycling performance in a temperate environment. Ten trained male cyclists [mean (SD) maximal oxygen uptake: 63.3(4.0) mL/kg/min; peak power output (PPO): 385(40) W; training: 10 (3) h/week] underwent a STHADe program consisting of 5 days of exercise (maximum 90 min/day) in a hot environment (40 °C, 50% RH) to elicit isothermic heat strain [rectal temperature 38.64(0.27) °C]. Participants abstained from fluids during, and 30 min after, HA sessions. Pre- and post-STHADe HA was evaluated during euhydrated fixed-intensity exercise (60 min) in hot conditions; the effect of STHADe on thermoregulation was also examined under temperate conditions (20 min fixed-intensity exercise; 22 °C, 60% RH). Temperate cycling performance was assessed by a graded exercise test (GXT) and 20-km time trial (TT). STHADe reduced thermal and cardiovascular strain in hot and temperate environments. Lactate threshold [Δ = 16 (17) W] and GXT PPO [Δ = 6 (7) W] were improved following STHADe (P < 0.05), but TT performance was not affected (P > 0.05), although there was a trend for a higher mean power (P = 0.06). In conclusion, STHADE can reduce thermal and cardiovascular strain under hot and temperate conditions and there is some evidence of ergogenic potential for temperate exercise, but longer HA regimens may be necessary for this to meaningfully influence performance.


Subject(s)
Bicycling/physiology , Body Temperature Regulation , Dehydration/physiopathology , Exercise/physiology , Heat Stress Disorders/physiopathology , Physical Conditioning, Human/physiology , Thermotolerance , Adult , Anaerobic Threshold , Exercise Test , Hot Temperature , Humans , Male , Young Adult
11.
Scand J Med Sci Sports ; 25(5): e459-71, 2015 Oct.
Article in English | MEDLINE | ID: mdl-25440756

ABSTRACT

Water-based activities may result in the loss of thermal comfort (TC). We hypothesized that in cooling water, the hands and feet would be responsible. Supine immersions were conducted in up to five clothing conditions (exposing various regions), as well as investigations to determine if a "reference" skin temperature (Tsk) distribution in thermoneutral air would help interpret our findings. After 10 min in 34.5 °C water, the temperature was decreased to 19.5 °C over 20 min; eight resting or exercising volunteers reported when they no longer felt comfortable and which region was responsible. TC, rectal temperature, and Tsk were measured. Rather than the extremities, the lower back and chest caused the loss of overall TC. At this point, mean (SD) chest Tsk was 3.3 (1.7) °C lower than the reference temperature (P = 0.005), and 3.8 (1.5) °C lower for the back (P = 0.002). Finger Tsk was 3.1 (2.7) °C higher than the reference temperature (P = 0.037). In cool and cooling water, hands and feet, already adapted to colder air temperatures, will not cause discomfort. Contrarily, more discomfort may arise from the chest and lower back, as these regions cool by more than normal. Thus, Tsk distribution in thermoneutral air may help understand variations in TC responses across the body.


Subject(s)
Extremities/physiology , Lumbosacral Region/physiology , Sensation/physiology , Skin Temperature/physiology , Thorax/physiology , Adult , Cold Temperature , Exercise/physiology , Healthy Volunteers , Humans , Immersion/physiopathology , Male , Protective Clothing , Water , Young Adult
12.
Scand J Med Sci Sports ; 25(2): 152-8, 2015 Apr.
Article in English | MEDLINE | ID: mdl-24433540

ABSTRACT

This study aimed to examine thermoregulation in different clothing assemblies during a representative cycling exercise protocol. Six men undertook cycling exercise simulating representative thermal exchange challenges while wearing low (LOW), intermediate (INT1 and INT2), or high (HI) amounts of clothing. Exercise was conducted at 14.5 °C, 46.8% relative humidity and included a "flat" [45 min at 35% peak power output (PPO), wind speed 8.3 m/s], "uphill" (30 min at 55% PPO, wind speed 3.6 m/s), and "downhill" (20 min at 50 W, wind speed 16.7 m/s) stage. Rectal temperature changed with the exercise stage and was independent of clothing assembly. In contrast, an "envelope" was evident for mean body temperature, resulting from differences in mean skin temperature between the LOW and HI conditions. The elevated mean body temperature in HI was associated with increased physiological "cost," in the form of increased sweat production and heart rate. Physiological cost provides a better index of clothing performance than deep body temperature in the "thermoregulatory zone," as a consequence sports clothing should attempt to optimize the balance between comfort and reduced physiological cost.


Subject(s)
Bicycling/physiology , Body Temperature Regulation/physiology , Clothing , Adult , Body Temperature , Environment, Controlled , Humans , Humidity , Male , Temperature
13.
Ergonomics ; 57(8): 1256-64, 2014.
Article in English | MEDLINE | ID: mdl-24784155

ABSTRACT

Wearing a lifejacket when immersed in water should support the wearer, maintaining their airway clear of the water. It is proposed that a retention system would improve airway protection by improving retention of the lifejacket around the torso. Study one (n = 10) quantified the performance of lifejackets immediately following a step into water from height when a lifejacket was worn with a crotch strap (two different tightness) and without a crotch strap. Airway freeboard was improved when wearing a crotch strap (P < 0.05) compared with no crotch strap. Study two used a manikin to examine the performance of lifejackets with and without a crotch strap during 3-h exposures to waves. During exposure to waves, the time taken to aspirate the lethal dose of seawater for drowning was doubled when wearing a crotch strap compared with the no-crotch-strap conditions (P < 0.001). Therefore, wearing a crotch strap (functioning retention system) on a correctly fitted lifejacket improves airway protection following accidental immersion and prolonged wave exposure.


Subject(s)
Drowning/prevention & control , Immersion , Protective Clothing , Adult , Equipment Design , Female , Humans , Male , Manikins , Water
14.
Eur J Appl Physiol ; 113(10): 2435-46, 2013 Oct.
Article in English | MEDLINE | ID: mdl-23263741

ABSTRACT

This paper examines the processes involved in the establishment of a minimum occupational fitness standard, with particular reference to the interplay that inevitably occurs between objective measurements and subjective decisions. The areas considered include: the determination of the critical task on which to base a standard; establishing minimum acceptable performance and methods of best practice for the execution of these tasks; determining the physical demands of a task and a reasonable relative workload; producing the final standard. Finally, the impact of the subjective component of the development of an occupational fitness standard on its defensibility is discussed. It is concluded that all standards involve some subjective aspects; the extent of these could be reduced by further research. In the meantime, it would be prudent for those developing standards to detail the rationale, methods and evidence by which subjective decisions were reached, to provide an audit trail for subsequent investigation.


Subject(s)
Occupational Health/standards , Physical Fitness , Employment , Humans , Occupational Medicine/methods , Occupational Medicine/standards , Personnel Selection/methods , Personnel Selection/standards , Practice Guidelines as Topic
15.
Int J Sports Med ; 29(11): 895-8, 2008 Nov.
Article in English | MEDLINE | ID: mdl-18418806

ABSTRACT

This study tested the hypothesis (H1) that surf swimming involves a quantifiable experience component. Sixty-five beach lifeguards with (n = 35) and without surf experience (n = 30) completed: a best effort 200-m swim in a 25-m pool, a calm and a surf sea; an anthropometric survey; maximum effort 30-s swim bench test; 50-m pool swim (25 m underwater). In both groups, time to swim 200 m was slower in calm seas than in the pool and slower in surf than in either calm seas or the pool (p < 0.05). Calm sea swim times of the two groups did not differ significantly, but the no experience group was, on average (Sp-pooled variance), 49 s (62) slower on the 200-m swim in the surf conditions (p < 0.05). A stepwise regression identified surf experience as a predictor of surf swim time (R(2) = 0.32, p < 0.01). It is concluded that there is a significant and quantifiable (18 %) experience factor in surf swimming. This limits the usefulness of pool swim times and other land-based tests as predictors of surf swimming performance. The hypothesis (H1) is accepted.


Subject(s)
Adaptation, Physiological , Swimming/physiology , Adolescent , Adult , Anaerobic Threshold , Analysis of Variance , Exercise Test , Female , Humans , Male , Oceans and Seas , Surveys and Questionnaires , Time Factors , Young Adult
16.
Resuscitation ; 75(2): 332-7, 2007 Nov.
Article in English | MEDLINE | ID: mdl-17574722

ABSTRACT

The present study examined the ability of the crew of small fast rescue boats to perform basic life support (BLS) at sea. Tests were undertaken aboard a 67m emergency response and rescue vessel (ERRV), a 9.1m (30ft) and 11.6m (38ft) fast rescue craft ("daughter craft" (DC)). It was hypothesised that the ability to perform BLS on a DC would be significantly impaired when compared with that seen on the ERRV. Nine DC crew volunteered for the study. These tests were undertaken in sea states ranging from 0.5 to 6 (13cm to 4m wave height). Wind speeds ranged between 0 and 35knots. The deterioration observed in the performance of BLS on board the DC compared to that seen on the ERRV was significant (P<0.05) and was due, in part, to a tendency to over-inflate during rescue breathing, and under-compress during BLS when on the DC. Chest compression (CC) was impaired significantly above a sea state 3 (wave height 61-92cm). It is concluded that the performance of BLS on small boats, in particular rescue breathing, is significantly adversely affected by two major factors, motion-induced interruption and early fatigue. As a consequence, the likelihood of conducting fully effective continuous BLS on a small boat in a seaway for any length of time, with a good chance of a successful outcome, is considered to be poor. However, this should not deter rescuers from attempting to make such efforts where practicable.


Subject(s)
Cardiopulmonary Resuscitation/instrumentation , Life Support Systems/standards , Rescue Work/methods , Ships , Adult , Equipment Design , Feasibility Studies , Humans , Male
17.
Undersea Hyperb Med ; 33(4): 291-7, 2006.
Article in English | MEDLINE | ID: mdl-17004416

ABSTRACT

Hyperbaric Escape Systems (HES) are used when saturation diving bells have to be evacuated and divers transported to safety. The aim of the present investigation was to determine the levels of metabolic CO2 production expected from the occupants of an HES in different wave states, and from this, to recommend a reasonable and safe requirement for scrubbing CO2 within an HES. The CO2 production and heart rate of 20 male subjects representing saturation divers were collected while they were seated in an HES seat, fixed to an inflatable rescue vessel. The vessel was tethered in a wave pool and longitudinal (L), perpendicular (P), and calm (C) sea conditions were reproduced. Heart rate did not differ between conditions (P=0.33) the mean (SD) heart rates (b x min(-1)) were: C: 71 (8.5); L: 74 (9); P: 75 (9). Carbon dioxide production was significantly higher (P=0.005) with the boat orientated perpendicular to the waves compared to the calm condition. The mean (plus 99% confidence interval) carbon dioxide production for each of the conditions was C = 319mL x min(-1) + (41mL x min(-1)) = maximum of 360mL x min(-1); L=374mL x min(-1) + (46mL x min(-1)) = maximum of 420mL x min(-1); P = 409mL x min(-1) + (57mL x min(-1)) = maximum of 466mL x min(-1). It is therefore recommended that a 12 person HES should be capable of scrubbing at least 8,053L of carbon dioxide in 24 hours. Thus, the current requirement for 8,415L in 24h is reasonable.


Subject(s)
Carbon Dioxide/metabolism , Diving/physiology , Motion , Adult , Heart Rate/physiology , Humans , Male , Rest/physiology
18.
Occup Med (Lond) ; 56(1): 12-7, 2006 Jan.
Article in English | MEDLINE | ID: mdl-16267102

ABSTRACT

BACKGROUND: No task-based fitness standard currently exists for beach lifeguards (BLGs). AIM: To formulate an easily administered fitness test for BLGs based on the physical demands identified in Phase 1 of the project (previous paper). METHODS: A range of anthropometric and land- and water-based (swimming pool and flume) fitness assessments were administered to 25 male and female volunteer subjects (13 BLGs from the UK). RESULTS: The mean (SD) VO(2max) (l/min) were 3.04 (0.61) for towing a casualty, 2.08 (0.53) for board paddling with a casualty and 2.97 (0.67) for freestyle swimming. A significant correlation (r = -0.82, P < 0.001) was identified between distance paddled in the sea in 3.5 min (established in Phase 1) and pool 400-m front crawl swim time and between towing VO(2max) and deltoid circumference/log(10) 400-m front crawl swim time (r = -0.83, P < 0.001). CONCLUSIONS: The regression identified allows the conclusion that if a BLG can swim 400-m front crawl in a pool in <7.5 min, he/she should be able to paddle 310 m in the sea in <3.5 min. Final recommendations for a fitness test for potential BLGs are presented.


Subject(s)
Exercise Test/methods , Rescue Work , Running/physiology , Swimming/physiology , Adolescent , Adult , England , Female , Humans , Male , Middle Aged , Oceans and Seas , Oxygen Consumption , Physical Fitness/physiology , Time Factors
19.
Occup Med (Lond) ; 56(1): 6-11, 2006 Jan.
Article in English | MEDLINE | ID: mdl-16275656

ABSTRACT

BACKGROUND: Although similar standards exist internationally to select beach lifeguards (BLGs), these are generally not based on a task analysis. To reduce the likelihood of drowning, a BLG should reach a casualty within 3.5 min (210 s). AIM: To quantify the physical demands of the most critical generic tasks undertaken by BLGs. METHODS: A survey of 91 BLGs identified sea swimming while towing a casualty, board paddling with a casualty, and casualty handling as the most demanding activities. Performance during beach running (200 m), swimming in the sea (200 m), board paddling in the sea (400 m), swimming in a pool (200 m freestyle and 25 m underwater with 25 m return) and simulated casualty handling were measured. RESULTS: The median area at sea patrolled by paddling and swimming was 400 m. The mean 200-m sea swim time was 3.1 min or 188 s (SD = 46 s) and 95% of the BLGs were able to swim 200 m in 3.5 min (n = 22). The mean time to paddle 400 m was 3.8 min or 226 s (SD = 35 s) and 30% of the BLGs were able to paddle 400 m in 3.5 min (n = 23). The 5th percentile paddling speed was 1.38 m/s, therefore, 95% of the BLGs tested should be able to paddle 289 m in 3.5 min. CONCLUSIONS: If only a rescue board is available, the area out to sea patrolled by a lifeguard should be reduced from 400 m to 300 m.


Subject(s)
Physical Endurance/physiology , Physical Fitness/physiology , Rescue Work , Swimming , Adolescent , Adult , England , Exercise Test , Female , Humans , Male , Middle Aged , Oceans and Seas , Running , Time Factors
20.
Eur J Appl Physiol ; 93(5-6): 708-13, 2005 Mar.
Article in English | MEDLINE | ID: mdl-15666176

ABSTRACT

The zone of thermal comfort was determined during normoxia and hypoxia in 15 healthy normothermic young subjects. Subjects dressed only in shorts/shorts and bikini top donned a water-perfused suit and assumed a supine position on a bench. The ambient temperature was maintained at a mean (SD) of 25.7 (0.3) degrees C. The thermal comfort zone was determined by increasing the temperature of the water perfusing the suit from cool to warm. During the heating process, subjects were instructed to report when their perception of the thermal stimulus provided by the suit changed from unpleasant to pleasant, and again from pleasant to unpleasant. The boundaries of the thermal comfort zone were assumed to be the temperatures of the water perfusing the suit at the time the subjects reported a change in the affective component of their thermal perception. In normoxia, subjects inspired room air and in hypoxia a gas mixture containing 10% O(2) in N(2). Tympanic temperature was similar in the normoxia and hypoxia conditions (P>0.05). The average (SD) lower and upper limits of the thermal comfort zone were 30.5 (1.5) and 34.7 (3.3) degrees C, respectively, during normoxia, and 30.5 (1.7) and 35.1 (3.4) degrees C, respectively, during hypoxia. No significant differences were observed between the normoxia and hypoxia conditions (P>0.05). Also, no gender-related differences were observed in the characteristics of the thermal comfort zone. The results of the present study indicate that acute hypoxic exposure simulated in the present study does not affect the zone of thermal comfort in humans.


Subject(s)
Hypoxia , Perception , Temperature , Adult , Body Temperature , Environment , Female , Humans , Male , Oxygen , Water
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