Active Immersion Vs Passive Immersion
Immersion Active is in the business of improving lives. Whether it’s the millions of older adults we touch through our marketing and sales or the people – of all ages – who have made a commitment to work with us, we put people first. Purpose We tested the hypothesis that both post-exercise and passive cold water immersion (CWI) increases PGC-1α and VEGF mRNA expression in human skeletal muscle. The present study did not identify a clear benefit in core temperature reduction for either hand cooling or forearm immersion when compared to passive cooling in a 24°C room, although a more rapid heart rate recovery was noted in the ARM and HAND groups when compared to passive cooling. Active versus passive cooling during work in.
IntroductionThermal protective clothing (TPC) worn by firefighters provides considerable protection from the external environment (e.g. Heat, flame) during structural fire suppression and heavy rescue activities. The evolution of TPC from a long outer coat and high boots to a shorter outer-coat combined with outer-pants has increased the level of protection but also reduces work time and speeds dehydration,.
In addition to the thermal burden, TPC also provides a barrier to heat loss, primarily the evaporation of sweat, resulting in an imbalance of heat production and heat loss and subsequent heat strain.The result of work in TPC can lead to multiple physiological derangements that must be identified and treated. The resulting hypohydration, cardiovascular strain, and heat strain after work in TPC must be reduced (by allowing rest and cooling), particularly between repeated fire suppression periods, to avoid compromising operational capability and firefighter safety. Since firefighters may be required to perform multiple bouts of work at a single incident, it is imperative that these recovery periods, known as fireground rehab, be implemented to decrease the chance of short- and potentially long-term negative health effects. Multiple studies have examined various active and passive devices to cool firefighters following work in TPC –. One study demonstrated that active cooling by forearm immersion reduces cardiovascular and thermal strain and increases work time in firefighters wearing TPC and self-contained breathing apparatus (SCBA) when compared to cooling by a fan coupled with a water mist or passive cooling. However, the rehab procedures in the Selkirk (2004) study were performed in a 35°C chamber which would simulate outdoor fireground rehab on a very warm day.Much of the industrialized world lies in the temperate regions between the tropics and the polar circles and exceedingly warm temperatures may only exist a few weeks to months each year.
Given a finite number of personnel available to perform fire suppression at any given incident and that finances available for equipment purchases are not limitless in the fire service, it is important to understand if the benefits available from active vs. Passive cooling in a warm environment are realized when working in cooler environments. Therefore, the present study examined heart rate and core temperature responses during the application of four active cooling devices, currently being marketed to the fire service, and compared them to passive cooling in a moderate temperature condition (approximately 24°C) and to an intravenous infusion of cold (4°C) normal saline. Study Design and PopulationEighteen subjects (14 males, 4 females) were recruited and provided written informed consent. Thirteen subjects were firefighters while the remaining subjects were fit individuals recruited from the university population and provided with the opportunity to become familiar with protective equipment. Subjects were compensated for their time at the midpoint and conclusion of the study. Prior to entering the protocol, subjects reported to the lab for a physical exam and an exercise stress test conducted by a study physician.
In addition to a physical exam, subjects had body fat percentage measured by three site skinfold analysis. Inclusion criteria were age 18–45 years while the exclusion criteria were existing heart or respiratory disease, medications known to alter cardiac response to exercise or thermoregulation, previous abdominal surgery, renal disease, Reynoud’s disease or other circulatory disease. Exercise Stress Test (EST)Prior to the first protocol visit, subjects performed a modified Storer-Davis protocol graded exercise stress test on a Monark 828E cycle ergometer (Vansbro, Sweden) to determine aerobic capacity (VO 2max) and cardiovascular function. Female subjects were required to take a urine pregnancy test prior to each testing day and excluded if a positive result was confirmed. Subjects were asked to refrain from caffeine, tobacco, alcohol, and exercise 12 hours before the stress test. During testing, an open circuit spirometer (MedGraphics Cardiorespiratory Diagnostic System with Breeze Suite Software, St. Paul, MN) calculated breath by breath analysis of oxygen consumption (VO 2).
The electronic analyzers were calibrated prior to each exercise test using standard reference gases. A twelve-lead ECG was obtained every three minutes during the protocol and post exercise to screen for undiagnosed ischemic disease presenting during exercise.
A cardiologist interpreted test results to identify ischemic changes or other electrocardiographic evidence of underlying cardiovascular disease that would result in exclusion from the protocol. Testing ProtocolThe testing protocol was designed to mimic an extended period of fire suppression that complied with the NFPA 1584: Standard on the Rehabilitation Process for Members During Operations and Training Exercises which recommends that firefighters use a maximum of two breathing air cylinders before submitting to on-scene rehabilitation (approximately 50 minutes total including the cylinder change) prior to a second work period. Other than the group assignment of cooling received during rehabilitation, all testing days were identical. The order of the cooling regimen was predetermined by random assignment.Subjects reported to the lab between 0800 and 1100 hours on six separate occasions, each visit separated by at least one week, to perform an exercise protocol in TPC. The lab was heated to 35.1 ± 2.7°C air temperature. Subjects were instructed to abstain from any food intake the morning of testing and were asked to refrain from alcohol, nicotine and caffeine for at least 12 hours before testing. Urine specific gravity (USG) was measured using a hand-held refractometer (ATAGO Ltd, Bellevue, WA) when the subject reported to the lab.
Subjects were required to be well hydrated (USG ≤ 1.025). Subjects were weighed nude on a digital balance. To assure equivalent pre-exercise nutrition, subjects received a standardized diet of 1 g/kg of body weight of carbohydrates of meal replacement bars (Clif Bar, Berkeley CA) and 400–600 ml of water one hour before testing. Midway through testing, this meal replacement bar was withdrawn from sale and a substitute with comparable nutrition content was used (Powerbar Harvest, Glendale, CA).Subjects were dressed in standard station wear (cotton-poly long pants, 100% cotton t-shirt) prior to donning the uniform and TPC. Subjects donned standardized thermal protective clothing consisting of turnout pants and coat (Body guard, Lion Apparel, Dayton OH), Nomex® hood, rubber bunker boots (Servus, Rock Island, IL), polycarbonate helmet (Paul Conway, Dayton, OH), and leather gloves.
Subjects wore SCBA (Firehawk®, MSA, Pittsburgh, PA). The SCBA mask was worn during the protocol but left open to room air. After donning TPC and SCBA, subjects stood on the treadmill while baseline measures of heart rate, respiratory rate, and core temperature were taken.Subjects performed a treadmill exercise protocol modified from a previous study of firefighter response to cooling devices that was designed to simulate the aerobic demands of fire suppression. Subjects initially walked at 4.5 km/hr on a 2.5% incline to mimic the exertion of fire suppression. After 20 minutes the treadmill was lowered to a level position and the speed was decreased to 2.5 km/hr for three minutes to mimic exiting the fire structure followed by a four minute standing period to simulate having their SCBA cylinder changed.
Following the standing period, the subjects again walked at 2.5 km/hr on a 0% incline for three minutes followed by a 20 minute bout of walking at 4.5 km/hr on a 2.5% incline to simulate returning to the fire structure for a second period of fire suppression. Total protocol length was 50 minutes (BOUT 1). Subjects ended BOUT 1 when they completed the 50-minute protocol or when one of the following termination criteria were achieved 1) respiratory rate 60 breaths per min, 2) heart rate exceeded age predicted maximum (220-age) + 10 bpm, 3) core temperature 39.5°C, 4) unsteady gait making it unsafe to continue treadmill exercise, or 5) subject request.
Heart rate, respiratory rate, and core temperature were recorded every two minutes during exercise.At the end of BOUT 1, subjects exited the heated room and doffed TPC. Subjects were immediately weighed nude. They were then redressed in the uniform with a dry shirt and instructed to rest in the semi-fowler position for a 20-minute period. Physiological MeasuresSubjects were fitted with a heart rate monitor (Polar Electro – USA, NY) placed around the chest. Core temperature was measured with an indigestible pill and radio receiver (HQ Inc, FL). Subjects took the pill eight hours before arrival to minimize the confounding influence of recently consumed food or fluid if the pill were still positioned in the stomach or upper portion of the small bowel.
This device provides a core temperature measurement that is intermediate to rectal and esophageal temperature. ResultsSubjects had normal EST and resting 12-lead ECG. Subject morphometrics and baseline characteristics are shown in. Male subjects were taller and heavier. However, no differences were noted in BMI or percent body fat. Overall, subjects possessed moderate cardiorespiratory capacity and mean fasting total cholesterol and triglycerides were within normal limits.
One subject dropped out of the study after being diagnosed by his primary care physician with a chronic illness unrelated to the study resulting in the loss of two tests. One subject began a trial becoming ill just prior to entering rehab. One subject dropped from the trial without explanation resulting in the loss of one trial. Changes during exerciseThe duration of exercise in BOUT 1 and BOUT 2 did not differ by device (F = 1.23, p = 0.293). However, the average duration of exercise in BOUT 2 following rehab was shorter than BOUT 1 (F = 64.5, p. Core temperature response during exercise before (panel A) and after (panel B) rehab.
Also shown is heart rate response during exercise before (panel C) and after (panel D) rehab. For both temperature and heart rate, all time comparisons different (p. Changes during rehabThe magnitude (°C) and rate (°C/min) of cooling during the 20-minute rehab period did not differ by device.
The proportion of subjects achieving the goal rehab temperature of 37.5°C varied between groups ranging from 31% (Passive) to 67% (IV). Menghitung jumlah data java netbeans. Serial core temperatures during rehab are shown in.
Although the overall magnitude of cooling did not differ, when considering the serial measurements across 20 minutes, there was an effect of both device (F = 7.57, p. Core temperature at rehab minute 0 for subjects ultimately reaching the core temperature of 37.5°C (open bars) and those not reaching target temperature (closed bars).
Groups are different (p. Heart rate response during rehab. PASSIVE cooling slower than ARM (p = 0.006), HAND (p = 0.012), and IV (p = 0.013). Heart rate lower at all time points when compared to minute 0 (p. DiscussionThis study compared four active cooling devices to cold intravenous saline and passive cooling in a 24°C room. This study is unique in that it examines a large number of cooling modalities currently marketed to the fire service in a controlled laboratory setting.
On average, subjects were not able to recover to a core temperature below 37.5°C during a 20-minute rehab period when provided rehydration and the opportunity to completely remove TPC for passive cooling. Additionally, active cooling devices did not enhance firefighter recovery following work in TPC when compared to passive cooling when resting in a 24°C room.It is well established that work in chemical protective and TPC results in hypohydration and cardiovascular stress,. If uncorrected, continued heat stress may lead to exertional heat illness including heat exhaustion and heat stroke. Additionally, heat stress sequellae may contribute to the increased cardiovascular events seen in firefighters performing fire suppression duties.
The National Fire Protection Association (NFPA) has recognized the importance of fireground rehab by elevating NFPA 1584 from a guideline to a standard in the most recent revision. However, other than one scientific study of firefighter cooling in the warm environment there is a paucity of research in this area using operationally relevant work times and conditions making it difficult to create evidence-based practices that can be applied to a wide range of operations and environmental conditions.In a previous study of rehab in a warm environment (35°C), active cooling blunted the rise in core temperature and extended work time when compared to passive cooling but could not correct the physiologic derangements (e.g. Tachycardia, heat strain) within a 20-minute rehab period. There are few studies comparing active cooling devices to passive cooling in a controlled moderate temperature environment such as could be created with an air-conditioned vehicle or portable shelter which are commonly employed on the scene. When compared to rehab in moderate temperatures, the data in the present investigation indicate that no device is superior to passive cooling in terms of subsequent exercise duration or physiological response following rehab, or in overall magnitude or rate of cooling during rehab.
Small advantages in the speed of recovery were identified in some of the devices employed during rehab. However, the clinical and operational significance of faster recovery is uncertain.The optimal rate of cooling during fireground rehab is not known, although from an operational standpoint it can be argued that the most rapid return of core temperature to baseline levels is desirable for situations requiring crews to rotate back into an incident. We have previously investigated the effect of a rapid infusion of cold saline in normothermic volunteers and reported that administration of 30 ml/kg of cold fluid into a peripheral arm vein produces approximately 1°C of core cooling. Increasing availability of cold saline in the prehospital setting for induction of therapeutic hypothermia following cardiac arrest makes this potential therapy available for other applications. In this report, we found that cold intravenous saline resulted in the earliest return of core temperature although the magnitude of cooling was not different from other less invasive methods.
Unlike previous studies in normothermic subjects, hyperthermic subjects reported intense discomfort in the upper extremity and shoulder during the infusion making this an unattractive rehab tool for the mildly hyperthermic firefighter.Alternative rehab modalities that are more commonly used in the fire service and are potentially easier to implement are forearm and hand immersion cooling. Both modalities take advantage of the extensive arteriovenous (AVA) anastomoses of the distal upper extremity. In a previous study of rehab in a warm environment with a similar exercise protocol as the present report, forearm and hand immersion was superior for extending work time and blunting the hyperthermic response when compared to both passive cooling and a fan coupled with a fine water mist. Another study of hand and forearm cooling used three 20–minute work periods with intervening 20-minute rehab periods at room temperature to investigate the capacity of 10°C and 20°C water to correct the hyperthermic response of exertion in TPC demonstrated that hand immersion in 10°C water, and forearm + hand immersion in both 10°C and 20°C water conferred lower core temperature during the bout of exercise following cooling.
However, these cooling trials were not different than the passive condition or hand immersion in 20°C at the end of any cooling period. At least part of the observed benefit in that study can be attributed to an afterdrop cooling effect in the opening minutes of the second and third exercise period following immersion. However, another study of hand immersion cooling following simulated firefighting activities also failed to reveal an advantage of hand cooling over removing TPC, drinking cold water, and sitting at room temperature.The present study did not identify a clear benefit in core temperature reduction for either hand cooling or forearm immersion when compared to passive cooling in a 24°C room, although a more rapid heart rate recovery was noted in the ARM and HAND groups when compared to passive cooling. The starting water temperature used in the present report was comparable to both studies but may be considerably cooler than what is available on the fireground. Our study differs from Selkirk et al principally by changing the rehab climate from warm and humid to more temperate conditions thereby improving the radiative and evaporative processes of passive cooling and by completely removing TPC. Our study also differs from previous reports by employing the actual device currently marketed to the fire service.
In one study of forearm immersion cooling, the authors report that the subjects immersed the upper extremities into a large water tank to provide a constant heat sink while in another, the subjects immersed their forearms into a calorimeter with an approximate volume of 36 liters. The device currently marketed to the fire service uses smaller water reservoirs placed in the arms of a folding chair and may have less capacity to absorb heat.The hand cooling device used in the present study also takes advantage of the AVA in the hand by having the subject grip a metal cone which is perfused with cold water while a mild vacuum is placed on the hand and is purported to encourage maximal blood volume in the blood vessels. However, given that the vessels should be dilated when core temperature is high the value of placing a vacuum on the hand is uncertain. A recent study compared the same device to passive cooling after 40 minutes of treadmill and upper body exercise.
A significant, although small, additional change in rectal temperature was noted in the hand cooling arm of their study but this was not evident until cooling had been applied for 35 minutes. It is unlikely that most fireground rehab sectors will hold asymptomatic individuals for this length of time if manpower must be rotated back into the incident.The fan is ubiquitous within the fire service.
Large ventilations fans are found on nearly every fire service vehicle tasked with structural fire suppression. A recent study of post-exercise cooling in hot humid conditions in athletes reported whole body fanning to be most effective at extracting heat when compared to other devices including hand immersion and a liquid cooled garment.
In that study, a larger fan was used and the subjects were cooled in the hot (31.2°C), humid (70% RH) room clothed only in short pants making it difficult to translate to fireground rehab practices. Another study found that a fan coupled with removing the TPC coat blunted the rise of core temperature when compared to simply unbuckling the coat during the rest phase. However, it is not clear what portion of the observed result was attributable to the fan vs.
The removal of the TPC coat. In the study of rehab in the warm environment, a misting fan partially restored core temperature during rest periods but was not as effective as forearm immersion.While fans are readily available on the fire scene, the misting fan marketed for fireground rehab exists only as a rehab tool and cannot be employed for fire suppression. We chose to examine a large cooling fan without using the misting attachment based on the widespread availability. While a standard fire service fan cannot employ the fine water mist, the use of misting feature should take environmental conditions into consideration. In Selkirk et al (2004), the misting fan likely improved convective heat loss but may have inhibited evaporative heat loss by raising the local relative humidity by 20%. The lack of clear benefit when compared to passive cooling does not recommend its routine use on the fireground when conditions are temperate. However, there was a clear preference for the fan by the subjects potentially indicating a perceptual benefit.Cooling vests have been examined in firefighters during work in TPC,.
However, we are unaware of studies using a powered cooling vest for fireground rehab. Use of cooling vests during fire suppression activities requires the firefighter to carry the additional weight of the vest that may include phase change material, cold packs, or a battery to operate a pump. Powered devices, such as the liquid perfused vest examined in the present study, are only practical in the rehab setting.
However, there was no clear benefit over passive cooling in 24°C air. LimitationsThere are several potential limitations that should be considered when interpreting these data or when implementing operational guidelines. Since this was a laboratory study we were able to measure core temperature which may not be possible in the field. Subjects completely removed the TPC ensemble during the rehab period to facilitate weighing.
This is not typically done on the fireground and will have enhanced the cooling enjoyed in the passive condition. However, firefighters can remove the TPC coat and push the TPC pants down over the boots while seated thereby exposing both the upper and lower extremities. Given the reported benefits of wearing short pants under TPC, the combination of short pants and partial removal of the TPC pants may further enhance passive cooling,.We were not able to fully investigate the cooling effect of cold saline due to the requirement of only replacing the volume of fluid lost to sweating. Although an average of 700 mL of cold saline was provided, a few subjects had minimal sweat losses in all conditions of the study resulting in only a few hundred milliliters of cold saline being infused during the IV condition. We have previously shown that hyperhydration induced with 30 mL/kg of intravenous normal saline prior to work in chemical protective clothing is well tolerated so larger volumes could have been provided during the rehab period. Although the discomfort would still be present, a larger infusion of cold saline would likely have resulted in greater cooling potentially returning the individual to the baseline core temperature within the allotted 20 minutes.
Emersion Vs Immersion
Similarly, we cannot comment on the effect of a large volume of room temperature saline although this may be an attractive therapy given the ability to replace even large volumes of fluid loss in a short period of time and it may provide a tangible amount of cooling. However, given the discomfort that accompanied cold saline infusion in hyperthermic individuals we would not recommend this as a routine practice but rather one that should be investigated as a therapy for exertional heat illness.There are other permutations of fireground rehab that we were not able to address in this single study. The 20-minute rehab period is typical in western Pennsylvania but may not be universal. A longer rehab period may allow for additional cooling and ultimately could demonstrate one device to be superior. Clearly, 20 minutes was not sufficient to provide full recovery of core temperature in our subjects. Additionally, there may be other devices with superior cooling properties that we were not able to study.
We chose devices that are being directly marketed to the fire service and to some degree are being used in the field. Finally, the study by Selkirk et al (2004) has clearly shown that passive cooling is not acceptable when rehab is performed in a warm environment.
It is possible that the HAND, VEST, or IV groups would have performed as well as forearm immersion in the Selkirk study when employed in a hot environment. In spite of these limitations, this is the first study to examine a wide array of cooling modalities and compare them to passive cooling in a temperate environment. ConclusionThe present study is the first to demonstrate no clear advantage between active cooling devices, cold intravenous saline, and passive cooling in a moderate temperature after treadmill exercise in TPC.
On average, subjects were not able to fully recover core temperature during a 20-minute rehab period when provided fluids and the opportunity to completely remove TPC. There may not be an advantage to employing active cooling devices to firefighters when the external temperature is below 24°C or if such a temperature can be provided through the use of air-conditioned shelters or vehicles. Further studies are required to verify these findings in the fiel. This study was funded by the FEMA Assistance to Firefighters Grant Program (EMW-2006-FP-02245) and Mine Safety Appliance. This study was also supported in part by Grant Number UL1 RR024153 from the National Center for Research Resources (NCRR), a component of the National Institutes of Health (NIH), and NIH Roadmap for Medical Research. The contents of this manuscript are solely the responsibility of the authors and do not necessarily represent the official view of FEMA, NCRR, or NIH.
The authors gratefully acknowledge Lion Apparel for a generous equipment grant supporting this study. Special thanks to our subjects who cheerfully endured a long and difficult protocol.
1 School of Biomedical Sciences and Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Australia. 2 Centre of Excellence for Applied Sport Science Research, Queensland Academy of Sport, Brisbane, Australia. 3 University of Queensland, School of Human Movement and Nutrition Sciences, Brisbane, Australia. 4 Liggins Institute, University of Auckland, Auckland, New Zealand. 5 Department of Biosciences, University of Oslo, Oslo, Norway. 6 Norwegian School of Sport Sciences, Oslo, Norway. 7 Faculty of Sport Sciences, Waseda University, Tokorozawa, Japan.
KEY POINTS:Cold water immersion and active recovery are common post-exercise recovery treatments. A key assumption about the benefits of cold water immersion is that it reduces inflammation in skeletal muscle. However, no data are available from humans to support this notion.
We compared the effects of cold water immersion and active recovery on inflammatory and cellular stress responses in skeletal muscle from exercise-trained men 2, 24 and 48 h during recovery after acute resistance exercise. Exercise led to the infiltration of inflammatory cells, with increased mRNA expression of pro-inflammatory cytokines and neurotrophins, and the subcellular translocation of heat shock proteins in muscle.
These responses did not differ significantly between cold water immersion and active recovery. Our results suggest that cold water immersion is no more effective than active recovery for minimizing the inflammatory and stress responses in muscle after resistance exercise.
ABSTRACT:Cold water immersion and active recovery are common post-exercise recovery treatments. However, little is known about whether these treatments influence inflammation and cellular stress in human skeletal muscle after exercise. We compared the effects of cold water immersion versus active recovery on inflammatory cells, pro-inflammatory cytokines, neurotrophins and heat shock proteins (HSPs) in skeletal muscle after intense resistance exercise. Nine active men performed unilateral lower-body resistance exercise on separate days, at least 1 week apart. On one day, they immersed their lower body in cold water (10°C) for 10 min after exercise.
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On the other day, they cycled at a low intensity for 10 min after exercise. Muscle biopsies were collected from the exercised leg before, 2, 24 and 48 h after exercise in both trials. Exercise increased intramuscular neutrophil and macrophage counts, MAC1 and CD163 mRNA expression (P. Upper panels show immunohistochemistry staining for αB‐crystallin in muscle fibres before exercise ( A) and at 2 h after exercise ( B). A fibre was considered positive if the staining inside the fibre was scattered and uneven (marked with red asterisks). Fibres were considered negative if the staining was homogeneous (all fibres in the left image). Lower panels show immunohistochemistry staining for myosin heavy chain IIA and IIX (SC71 antibody) in neighbouring sections.
Active Immersion Vs Passive Immersion Training
Before exercise, there was more αB‐crystallin protein present in type I fibres (marked ‘I’ in panel B, C and D), whereas after exercise, the scattered αB‐crystallin staining was found mainly in type II fibres (panel D). Scale bar represents 100 μm. Colour figure can be viewed at wileyonlinelibrary.com.