Precooling Methods Research Articles

Internal and external cooling methods and their effect on body temperature, thermal perception and dexterity.

ObjectiveThe present study aimed to compare a range of cooling methods possibly utilised by occupational workers, focusing on their effect on body temperature, perception and manual dexterity.MethodsTen male participants completed eight trials involving 30 min of seated rest followed by 30 min of cooling or control of no cooling (CON) (34°C, 58% relative humidity). The cooling methods utilised were: ice cooling vest (CV0), phase change cooling vest melting at 14°C (CV14), evaporative cooling vest (CVEV), arm immersion in 10°C water (AI), portable water-perfused suit (WPS), heliox inhalation (HE) and ice slushy ingestion (SL). Immediately before and after cooling, participants were assessed for fine (Purdue pegboard task) and gross (grip and pinch strength) manual dexterity. Rectal and skin temperature, as well as thermal sensation and comfort, were monitored throughout.ResultsCompared with CON, SL was the only method to reduce rectal temperature (P = 0.012). All externally applied cooling methods reduced skin temperature (P<0.05), though CV0 resulted in the lowest skin temperature versus other cooling methods. Participants felt cooler with CV0, CV14, WPS, AI and SL (P<0.05). AI significantly impaired Purdue pegboard performance (P = 0.001), but did not affect grip or pinch strength (P>0.05).ConclusionThe present study observed that ice ingestion or ice applied to the skin produced the greatest effect on rectal and skin temperature, respectively. AI should not be utilised if workers require subsequent fine manual dexterity. These results will help inform future studies investigating appropriate pre-cooling methods for the occupational worker.

The effect of ice slurry ingestion on intermittent activity and a run to exhaustion in the heat

Major competitions are often staged in hot environments. However, the body's ability to dissipate heat is compromised during heat stress resulting in a concomitant rise in core temperature (Tc), ultimately leading to impaired performance. Precooling methods such as ice vests and cold water immersion are employed before competition, to lower Tc and increase heat storage before a critical Tc is reached. However, there are numerous practical limitations meaning pre-existing methods are impractical for use in a field setting. Ice slurry ingestion has been investigated as a more practical precooling method and has enhanced endurance performance [1], however research has yet to determine its effects upon intermittent activity. Therefore the aim of this study was to determine the efficacy of ice slurry ingestion as a precooling method prior to intermittent activity and a run to exhaustion in the heat.

Performing in the heat: a new practical midcooling method

Pre-cooling aims to decrease body core temperature prior to [1] and decelerate its rise during exercise preventing excessive hyperthermia [2]. Exercise time to exhaustion in a hot environment is inversely related to the initial body temperature and directly affected by the rate of heat storage [3]. Despite the fact that all ball games involve intermittent activity with at least one long brake among periods, the majority of existing pre-cooling methods are applied before event initiation and use aggressive techniques (cold-water immersion, ice cubes, ice vests). This practice is cumbersome and may initially induce hypothermia, ensuing thermo genesis and discomfort. The purpose of this study was to investigate the effect of a new, practical method for cooling the body during the break (mid-cooling) of a prolonged, high-intensity intermittent exercise in the heat.

Effect of Different Pre-Cooling Methods on the Quality and Shelf Life of Broccoli

This study aimed to evaluate the production of gas and volatile fatty acids when glycerin was used to replace four forage species through the use of a semi-automated technique in vitro. The experimental design included 4 treatments and 4 replications. The treatments consisted of increasing levels of glycerin (0%, 30%, 50% and 70%), which was used to replace the forage plants elephant grass, sugar cane, corn silage and Brachiaria grass. Replacement of the Brachiaria and elephant grasses with glycerin affected the production of methane, carbon dioxide and ammonia nitrogen and had a positive effect on forage quality (p<0.05). With the addition of glycerin, the values for acetate production decreased (p<0.05); however, in elephant grass, when glycerin was increased to 50%, the acetate production increased from 26.51 to 26.62 and 28.60 (p<0.05). The inclusion of approximately 30% glycerin in the diet of ruminants is recommended because the inclusion of glycerin at this level had a qualitative effect on levels of methane, carbon dioxide, volatile fatty acids and ammonia nitrogen.

Forced-air, vacuum, and hydro precooling of cauliflower (Brassica oleracea L. var. botrytis cv. Freemont): part I. determination of precooling parameters

The aim of the present study was to precool cauliflower using forced-air, vacuum and high and low flow hydro cooling methods. The weight of the precooled cauliflower heads (5000±5 g) was measured before they were placed in standard plastic crates. Cauliflower heads, whose initial temperature was 23.5 ± 0.5 oC, were cooled until the temperature reached at 1 oC. During the precooling process, time-dependent temperature and energy consumption were measured, and during vacuum precooling, the decreasing pressure values were recorded, and a curve of time-dependent pressure decrease (vacuum) was built. The most suitable cooling method to precool cauliflower in terms of cooling time and energy consumption was vacuum, followed by the high and low flow hydro and forced-air precooling methods, respectively. The highest weight loss was observed in the vacuum precooling method, followed by the forced-air method. However, there was an increase in the weight of the cauliflower heads in the high and low flow hydro precooling method. The best colour and hardness values were found in the vacuum precooling method. Among all methods tested, the most suitable method to precool cauliflower in terms of cooling and quality parameters was the vacuum precooling method.

Precooling Methods and Their Effects on Athletic Performance

Precooling is a popular strategy used to combat the debilitating effects of heat-stress-induced fatigue and extend the period in which an individual can tolerate a heat-gaining environment. Interest in precooling prior to sporting activity has increased over the past three decades, with options including the application (external) and ingestion (internal) of cold modalities including air, water and/or ice, separately or in combination, immediately prior to exercise. Although many studies have observed improvements in exercise capacity or performance following precooling, some strategies are more logistically challenging than others, and thus are often impractical for use in competition or field settings. The purpose of this article was to comprehensively evaluate the established precooling literature, which addresses the application of cooling strategies that are likely to enhance field-based sports performance, while discussing the practical and logistical issues associated with these methods. We undertook a narrative examination that focused on the practical and event-specific application of precooling and its effect on physiological parameters and performance. Relevant precooling literature was located through the PubMed database with second- and third-order reference lists manually cross matched for relevant journal articles. The last day of the literature search was 31 January 2012. Relevant studies were included on the basis of conforming to strict criteria, including the following: (i) cooling was conducted before exercise; (ii) cooling was conducted during the performance task in a manner that was potentially achievable during sports competition; (iii) a measure of athletic performance was assessed; (iv) subjects included were able bodied, and free of diseases or disorders that would affect thermoregulation; (v) subjects were endurance-trained humans (maximal oxygen uptake [[Formula: see text]O(2max)] >50ml/kg/min for endurance protocols); (vi) cooling was not performed on already hyperthermic subjects that were in immediate danger of heat-related illnesses or had received passive heating treatments; (vii) drink ingestion protocols were used for the intended purpose of benefiting thermoregulation as a result of beverage temperature; and (viii) investigations employed≥six subjects. Initial searches yielded 161 studies, but 106 were discarded on failing to meet the established criteria. This final summary evaluated 74 precooling treatments, across 55 studies employing well trained subjects. Key physiological and performance information from each study was extracted and presented, and includes respective subject characteristics, detailed precooling methods, exercise protocols, environmental conditions, along with physiological and performance outcomes. Data were presented in comparison to respective control treatments. For studies that include more than one treatment intervention, the comparative results between each precooling treatment were also presented. The practical benefits and limitations of employing each strategy in the field and in relation to sports performance were summarized. Clear evidence of the benefits for a range of precooling strategies undertaken in the laboratory setting exists, which suggest that these strategies could be employed by athletes who compete in hot environmental conditions to improve exercise safety, reduce their perceived thermal stress and improve sports performance. This review did not include a systematic assessment of the study quality rating and provided a subjective assessment of the pooled outcomes of studies, which range in precooling methodologies and exercise outcomes. The wide range of research designs, precooling methods, environmental conditions and exercise protocols make it difficult to integrate all the available research into single findings. Most laboratory studies have shown improvements in exercise performance following precooling and the emergence of strategies that are practically relevant to the field setting now allow scientists to individualize relevant strategies for teams and individuals at competition locations. Future research is warranted to investigate the effectiveness of practical precooling strategies in competition or field settings.

Predictive pre-cooling of thermo-active building systems with low-lift chillers

This article describes the development and experimental validation of a data-driven model predictive control algorithm that optimizes the operation of a low-lift chiller, a variable-capacity chiller run at low pressure ratios, serving a single zone with a thermo-active building system. The predictive control algorithm incorporates new elements lacking in previous chiller pre-cooling control optimization methods, including a model of temperature and load-dependent chiller performance extending to low-pressure and part-load ratios and a data-driven zone temperature response model that accounts for the transient thermal response of a concrete-core radiant floor thermo-active building system. Data-driven models of zone and concrete-core thermal response are identified from monitored zone temperature and thermal load data and combined with an empirical model of a low-lift chiller to implement model predictive control. The energy consumption of the cooling system, including the chiller compressor, condenser fan, and chilled-water pump energy, is minimized over a 24-h look-ahead moving horizon using the thermo-active building system for thermal storage and radiant distribution. A generalized pattern-search optimization over compressor speed is performed to identify optimal chiller control schedules at every hour, thereby accomplishing load shifting, efficient part-load operation, and cooling energy savings. Results from testing the system's sensible cooling efficiency in an experimental test chamber subject to the typical summer week of two climates, Atlanta, GA, and Phoenix, AZ, show sensible cooling energy savings of 25% and 19%, respectively, relative to a high efficiency, variable-speed split-system air conditioner.

Effects of different precooling techniques on repeat sprint ability in team sport athletes

This study aimed to compare the simultaneous use of internal and external precooling methods with singular methods and their effect on repeated sprint cycling in hot/humid conditions. Twelve male team sport players completed four experimental conditions, initially involving a 30-min precooling period consisting of either a cooling jacket (J); ingestion of an ice slushy ice slushy; combination of cooling jacket and ice ingestion (J + ice slushy); or control (CONT). This was followed by 70 min of repeat sprint cycling (in~35°C, 60% relative humidity [RH]), consisting of 2×30-min halves, separated by a 10-min half-time period where the same cooling method was again used. Each half comprised 30×4 s maximal sprints on 60 s, interspersed with sub-maximal exercise at varying intensities. Total mean power and work performed were significantly higher (p = 0.02) in J + ice slushy (233.6±31.4 W) compared to ice slushy (211.8±34.5 kJ), while moderate effect sizes (ES: d = 0.67) suggested lower core temperatures (TC) in J + ice slushy (36.8±0.3°C) compared to J (37.0±0.3°C) and CONT (37.0±0.3°C) following precooling. A moderate ES (d = 0.57) also indicated lower TC in J + ice slushy (38.2±0.3) compared to ice slushy (38.4±0.4°C) after half-time cooling. Change (Δ) in mean skin temperature over half-time cooling was significantly greater (p = 0.036) for J (1.0±0.4°C) compared to ice slushy (0.5±0.5°C), and ES (d = 0.5–1.10) also suggested a greater Δ for J compared to the other conditions. Sweat loss was significantly greater (p < 0.05) in ice slushy and J + ice slushy compared to J and CONT. In conclusion, a combination of (external and internal) body cooling techniques may enhance repeated sprint performance in the heat compared to individual cooling methods.

Pre-cooling systems for small-scale producers

Purpose of review: To identify pre-cooling systems and cooling methods that are suitable for smaller scale horticultural producers Findings: A range of pre-cooling systems are available for small-scale horticultural producers and their suitability is described, in terms of availability, ease of use, capital cost, energy requirements. Expected benefits of using pre-cooling are also discussed. Limitations: Many of the mobile pre-cooling systems currently available on the market have been developed by commercial companies and most have not been scientifically evaluated in comparison to known stationary systems such as a cold wall. There is relatively little published information about the suitability of small-scale hydro-cooling, evaporative cooling and mobile forced-air cooling systems, especially regarding the range of crops and environments found in developing countries. Directions for further research: Future research needs include identification and characterization of lower cost pre-cooling methods and continued efforts to improve their cooling efficiency and reduce their energy use. Efforts to standardize and test management practices that conserve energy should be undertaken in order to further improve financial benefits.

Precooling techniques and applications for horticultural products — a review

One of the most important factors affecting the postharvest life and quality of horticultural crops is temperature. Quality loss after harvest occurs as a result of physiological and biological processes, the rates of which are influenced primarily by product temperature. As the maintenance of market quality is of vital importance to the success of the horticultural industry, it is necessary not only to cool the product but to cool it as quickly as possible after harvest. The process of precooling is the removal of field heat which arrest the deteriorative and senescence processes so as to maintain a high level of quality that ensures customer satisfaction. This paper provides a critical review to portray precooling as an intricate part of temperature management and to highlight the importance of its utilisation for extending the shelf life and maintaining the quality of horticultural products with emphasis on cut flowers. Various different precooling methods are depicted with the benefits and ambiguities of each shown. The applicability and cooling efficiency of each are also illustrated. Through this review, it is aimed to promote interest in precooling and encourage its use on a more widespread basis.