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Building and Environment xxx (2014) 1e5

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Effectiveness of an indoor preparation program to increase thermal resilience in elderly for heat waves Hein A.M. Daanen a, b, c, *, Janine A. Herweijer b a

TNO, PO Box 23, 3769ZG Soesterberg, The Netherlands MOVE Research Institute, Faculty of Human Movement Sciences, VU University, Van der Boechorststraat 9, 1081BT Amsterdam, The Netherlands c AMFI e Amsterdam Fashion Institute, CREATE-IT Applied Research, Amsterdam University of Applied Sciences, Mauritskade 11, 1091 GC Amsterdam, The Netherlands b

a r t i c l e i n f o

a b s t r a c t

Article history: Received 18 January 2014 Received in revised form 23 March 2014 Accepted 13 April 2014 Available online xxx

Elderly indoors can be subject to considerable heat strain during heat waves. We investigated if a short indoor acclimation (HA) program leads to improved resilience to heat. Although full HA takes about ten days, the main changes occur in the first days, leading to reduced heat strain with similar stress. This study investigates changes after 3 days HA in 8 elderly (>75 y) and 8 young (20e30 y) females. The pretest (Monday) and post-test (Friday) was a 20-min 50 W cycle exercise test in 35 ! C/40% relative humidity (RH); the indoor preparation program or HA consisting of one hour exercise in the same climate aimed at reaching a gastrointestinal temperature (Tgi) of 38 ! C. HA did not result in any changes in Tgi, mean skin temperature, heart rate, weight loss or thermal sensation. The elderly felt more fatigued but evaporated 28% less sweat than the young group during the tests. We conclude that 3-day HA for one hour daily is insufficient to cause physiological benefits in young and elderly females. ! 2014 Elsevier Ltd. All rights reserved.

Keywords: Heat strain Elderly Sweat rate Age Acclimation Heat

1. Introduction In the framework of the Dutch Climate Proof Cities program, research is initiated to investigate the effect of hot cities on human health [1]. The ambient temperature in cities shows a steady increase in ambient temperature due to global warming and the urban heat island effect. The increased ambient temperatures are reflected in the indoor climate. Indoor temperature and indoor humidity behave as a low-pass filter of ambient temperature and humidity [2]: the amplitude is reduced and a time delay is introduced. The indoor climate, in combination with the worn clothing and daily activity, forms the main thermal stressor for humans in hot periods. Humans maintain their body core temperature in a narrow range of 36.8e37.7 ! C in rest [3]. In warm circumstances, heat loss is compromised and body core temperature may increase to levels above this range, leading to a reduction in performance and a threat to human health. The increase in body core temperature depends

* Corresponding author. TNO, PO Box 23, 3769ZG Soesterberg, The Netherlands. Tel.: þ31 888 665 948. E-mail address: hein.daanen@tno.nl (H.A.M. Daanen).

on local climate (hot humid situations with sunshine and low wind speeds are the worst), clothing insulation and water vapour permeability, exercise intensity and personal factors like acclimation status. It is well documented that repeated exposure to heat, in particular in combination with exercise, leads to functional adaptations, which lowers thermal strain. The trigger for heat acclimation is a prolonged increased body core temperature [4]. The best way to achieve this, is to perform physical exercise: heat production often exceeds 1000 W and heat loss mechanisms do not fully compensate the heat production, so that the core temperature remains elevated. This so-called (heat) acclimation is defined as a method to acquire physiological adaptations to heat in an artificial environment [5]. The rate of acclimation induction follows a logarithmic path: the changes in the initial days exceed those in the later days of the acclimation program. The physiological systems adapt at a different rate; the heart rate and plasma volume changes occur first, followed by the reduction in core temperature, and the adjustments in sweat rate and composition adapting last [6]. Full acclimation generally takes about 10 days [7], but most changes are observed during the first days [8,9]. Sunderland et al. [10] showed that four sessions with 30e45 min training in the heat (30 ! C, 24% relative humidity (RH)) resulted in a lower core temperature in

http://dx.doi.org/10.1016/j.buildenv.2014.04.010 0360-1323/! 2014 Elsevier Ltd. All rights reserved.

Please cite this article in press as: Daanen HAM, Herweijer JA, Effectiveness of an indoor preparation program to increase thermal resilience in elderly for heat waves, Building and Environment (2014), http://dx.doi.org/10.1016/j.buildenv.2014.04.010


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H.A.M. Daanen, J.A. Herweijer / Building and Environment xxx (2014) 1e5

females. Weller et al. [11] showed that 50% of the total drop in heart rate over 10 days of acclimation was observed after three days. Acclimation is a standard procedure prior to competitive events in the heat, but it may also be useful in preparation for heat waves. During the 2010 heat wave in The Netherlands resting intestinal temperatures exceeding 38 ! C were recorded in elderly during the day [2], illustrating the considerable thermal strain that occurs in hot days. In ages under 65 heat tolerance is related to fitness level and not to age [12,13], but climate related mortality is eminent in the elderly over 75 years of age [14] in particular when confined to bed [15]. No studies are known to us that investigated acclimation and thermal strain in elderly over 75 years, the vulnerable part of the population during heat waves [16]. Heat mitigation strategies are based on reduction of the impact of ambient climate on indoor climate, for instance by changing the orientation, ventilation, structure or colour of the buildings that humans live in (e.g. Ref. [17]). In this way vulnerable groups, like the elderly, will experience less heat stress. It is, however, hardly investigated if elderly can adapt to repeated heat stress and thus reduce heat strain. If a heat wave is foreseen by the meteorological offices and if the possibility exists to acclimate elderly to heat, dedicated acclimation programs may be followed by elderly under controlled conditions, such as in elderly homes. The physiological adaptations that this preparation program generates, such as lower heart rate and body core temperature and higher sweat rates, will lower the heat strain during the heat wave and this may be reflected in lower mortality rates. Therefore, we conducted an experiment to evaluate if three days of acclimation involving exercise in the heat may lower thermal strain in subjects aged over 75 years of age. Only females were included since they constitute the major part of the elderly population. The participants were their own control: heat tolerance changes were investigated with and without an acclimation period. As a reference group, females aged 20e30 years participated. The acclimation period was set at three days and used the controlled hyperthermia model [8]. Previously, four days was shown to be sufficient to induce changes [10] and we wanted the period to be as short as possible to induce high predictive values for the heat wave. Therefore, we selected three acclimation days. Moreover, it cannot be excluded that the pre-test day also helped to generate some acclimation effects in which case the acclimation period may be considered to last 4 days. Exercise was performed during acclimation to maintain core temperatures at sufficient high levels for acclimation [4]. We hypothesize that both young females and females over 75 years will show a reduction in heart rate, but no changes in sweat rate and core temperature due to three days of acclimation. Heart rate is the most sensitive parameter for heat acclimation [11]. If the heart rate in rest and during exercise drops due to acclimation, this is a sign that effective adaptation to heat is possible and that the heat strain during a heat wave may be reduced in this way. 2. Methods 2.1. Subjects Eight female subjects aged over 75 (mean age 78.3 # 2.7 years, stature 166 # 8 cm, body mass 73 # 14 kg, body mass index 26.5 # 3.9 kg/m2, body surface area 1.81 # 0.20 m2 [18]) and eight female subjects aged 20e30 (mean age 24.8 # 2.9 years, stature 172 # 5 cm, body mass 72 # 14 kg, body mass index 24.0 # 3.4 kg/ m2, body surface area 1.84 # 0.18 m2) participated voluntarily in this study. The elderly group had a Morton Mobility Index (DEMMI) ranging from 74 to 100 (86 # 10), which means that they had a good

mobility for their age [19]. The DEMMI is an easy uni-dimensional measure of mobility based on 15 items from bed bound to independent mobility. The study was approved by the Medical Ethics Committee of Utrecht University Medical Center. The elderly subjects were screened on having no contra-indications to exercise testing as judged by a physician based on assessment of medical history, physical examination and the results of the 12-lead ECG examination. The elderly did not use medicine related to thermal regulation (e.g. beta blockers). The menstrual cycle phase of female subjects aged 20e30 was recorded and the last day of menstruation preceded the first day of test with 19 # 13 days. One subject had irregular menstruation. The variation was such that order effects are unlikely. 2.2. Protocol In a balanced cross-over study the elderly and young subjects participated in two 5-day measurement periods with three weeks recovery in between. The subject started at the same time of day. The subjects performed a heat strain test on day 1 and 5 with and without a acclimation protocol at days 2, 3 and 4. All subjects came for their first heat strain test on Monday. Half of the group of subjects started with acclimation at day 2, 3 and 4 and the other half started without acclimation. All subjects participated in a second heat strain test on Friday. The procedure was repeated after 4 weeks (three weeks in between) but then the subjects acclimatized that did not acclimatize before and reverse. The subjects were dressed in underwear, an oversized T-shirt, shorts, socks and shoes. Each day the participants arrived at the lab at least 30 min before entering the climatic chamber to prepare for the measures. The participants ingested a disposable core temperature capsule (Jonah, Hidalgo, Cambridge, UK) to measure gastrointestinal temperature, however, only if the pill taken the day before was not detected anymore. The subjects were equipped with a Hidalgo Equivital" Physiological Monitor system (Hidalgo, Cambridge, UK) to record gastrointestinal temperature (Tgi) and heart rate (HR) at 15-s intervals. These measurements continued until the end of the trial. To determine mean skin temperature (Tsk), four iButtons (DS1922L, Maxim Integrated Products Inc, Sunnyvale, CA, USA) were taped to the skin (neck, right scapula, right shin, left hand) using sweat-proof tape (Fixomull stretch, BSN Medical, Hamburg, Germany). The resolution was set to 0.0625 ! C. Tsk was calculated using weighing factors or 0.28 for the neck, scapula and shin and 0.16 for the hand [20]. Mean body temperature (Tb) was calculated as a weighed average of Tgi (0.8) and Tsk (0.2) [21]. The heat strain test and the acclimation protocol started with the following procedure. Just prior to entering the climatic chamber, the subject was weighed using a Sartorius balance (1 g resolution). Subjects would then enter the climatic chamber and sit for 30 min in the chamber set at 35 ! C/40% relative humidity to get accustomed to the ambient conditions. Hereafter, they would start exercising for 20 min at a work rate of 50 W using a Lode Excalibur cycle ergometer (Lode, Groningen, The Netherlands) in the pre- and post-test. On the acclimation days the subject started the exercise on the ergometer with an initial load of 50 W for at least 5 min; thereafter, the load was decreased or increased in such a way that a core temperature above 38 ! C was reached and maintained within 38e38.5 ! C. This method is called the controlled hyperthermia of isothermal strain model and preferred over traditional methods with fixed work load [8]. Sixty minutes after the start of exercise the acclimation period was ended. Every 10 min the subject would rate Thermal Sensation (TS) (9-point scale ranging from $4 very cold to þ4 very hot) and Rating of Perceived Exertion (RPE) [22]. Heart rate and temperatures were registered and monitored

Please cite this article in press as: Daanen HAM, Herweijer JA, Effectiveness of an indoor preparation program to increase thermal resilience in elderly for heat waves, Building and Environment (2014), http://dx.doi.org/10.1016/j.buildenv.2014.04.010


H.A.M. Daanen, J.A. Herweijer / Building and Environment xxx (2014) 1e5

continuously. On all days immediately after the exercise, the subject would be weighed again to determine body fluid loss. 2.3. Statistical analysis Acclimation effects were analysed using nested ANOVA of the GLM module of Statistica [23] (participants nested in the old/young group). Dependent variables were Tgi, Tsk, Tb, HR and TS at the start and end of exercise, RPE and weight loss. Only data for the pre/posttest were analysed, the acclimation sessions served as an intervention. Independent factors were age group (elderly, young), pree post-test and acclimatisation week (yes/no). Acclimation effects are observed as a significant interaction between acclimation and pre/ post-test: this means no differences between pre/post for the control situation and differences between the pre/post-tests for the acclimatised situation.

3

RPE was considerable higher (15.0 # 2.2 versus 11.9 # 2.1) (F(1,42) ¼ 10.0, p < 0.01). There was no significant interaction between pre/post-test and acclimation for any of the variables. This means that no physiological adaptations could be observed due to the acclimation intervention. There was a significant interaction between age and acclimation for HR at the end of exercise (F(1,42) ¼ 5.8, p < 0.05). HR in the young group was 9 beats per minute lower in the acclimation week than in the control week (((134 þ 132)/2 $ (126 þ 122)/2) in Table 1); in the elderly it was 6 min$1 higher. The same interaction was observed for Tsk at the end of exercise (F(1,42) ¼ 12.2, p < 0.005). Tsk at the end of exercise was 0.21 ! C higher in the acclimation week, while it was 0.13 ! C lower for the young group. Tsk at the end of exercise was slightly lower in the post-test than in the pre-test (F(1,42) ¼ 5.2, p < 0.05).

3. Results

4. Discussion

All subjects were able to successfully perform the pre- and posttests. Some elderly had difficulties to maintain the load during acclimation. In over half of the cases the cycling power had to be turned down to 30 W for the elderly. The average maximum power during acclimation was 55 # 7 W for the elderly and 78 # 16 W for the young group. During acclimation not all subjects reached a core temperature above 38 ! C. One young subject exceeded 38 ! C only during one acclimation day. Five elderly and three young participants exceeded 38 ! C on two acclimation days and seven subjects (four young and three elderly) exceeded the 38 ! C threshold on all three acclimation days. Tgi, Tsk, TS and HR during the acclimation days are shown in Fig. 1. The physiological variables determined during the pre- and post-test are summarized in Table 1. Elderly subjects lost 28% less weight during the pre- and posttest than the younger group (F(1,42) ¼ 6.59, p < 0.05) and their

The hypothesis that a short acclimation protocol leads to acclimation effects in heart rate could not be confirmed. None of the investigated variables showed any significant change from the pretest on Monday to the post-test on Friday. Even heart rate, one of the first variables that show changes in acclimation [6] remained essentially unchanged. Three days of acclimation (or four if we include the possibility that some acclimation may have occurred due to the exercise in the heat on Monday) were insufficient to lead to adaptations for young and elderly females. Sunderland et al. [10], observed acclimation effects in females after four short sessions in the heat, but the days in the heat were interspaced with days of rest during which physiological adaptations could take place. In contrast to our hypothesis, we did not observe physiological changes to heat. The stimulus for heat acclimation may not have been sufficient in our study due to the relative short period of

Fig. 1. Mean Gastrointestinal (GI) temperature (! C) (panel a), Mean Skin Temperature (! C) (panel b), Heart Rate (min$1) (panel c) and Thermal Sensation (arbitrary units) (panel d) plotted for time (min) averaged over three days of acclimation and eight female subject aged 20e30 years and eight female subjects aged over 75 years. Vertical bars indicate the 95% confidence interval of the mean. Time 0 min is the start of exercise.

Please cite this article in press as: Daanen HAM, Herweijer JA, Effectiveness of an indoor preparation program to increase thermal resilience in elderly for heat waves, Building and Environment (2014), http://dx.doi.org/10.1016/j.buildenv.2014.04.010


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H.A.M. Daanen, J.A. Herweijer / Building and Environment xxx (2014) 1e5

Table 1 Physiological variables averaged over eight young and eight elderly participants with the standard deviation for the pre-test (Monday) and post-test (Friday) with and without acclimation to heat. Elderly

Young

Control

Weight loss (kg) Tb start (! C) Tb end (! C) Tgi start (! C) Tgi end (! C) Tsk start (! C) Tsk end (! C) Core-skin gr. (! C) HR start (min$1) HR end (min$1) TS RPE

Acclimation

Control

Acclimation

Pre

Post

Pre

Post

Pre

Post

Pre

Mean # SD

Mean # SD

Mean # SD

Mean # SD

Mean # SD

Mean # SD

Mean # SD

Mean # SD

0.11 36.7 37.3 36.9 37.7 35.7 35.3 2.4 91 113 2.8 14.8

0.11 36.8 37.1 37.1 37.6 35.6 35.4 2.2 83 125 3.1 15.1

0.09 36.8 37.3 37.1 37.7 35.6 35.6 2.1 84 125 2.9 15.4

0.12 36.8 37.2 37.1 37.6 35.7 35.5 2.1 91 124 2.9 14.9

0.13 36.8 37.2 37.0 37.6 35.9 35.6 1.9 93 134 2.6 11.6

0.15 36.9 37.2 37.2 37.7 35.8 35.5 2.2 91 132 2.4 12.4

0.16 36.9 37.1 37.1 37.5 35.9 35.5 2.0 94 126 2.8 11.8

0.16 36.9 37.1 37.1 37.6 35.8 35.3 2.3 93 122 2.3 12.0

# # # # # # # # # # # #

0.04 0.5 0.3 0.7 0.4 0.3 0.4 0.6 9 20 0.7 1.8

# # # # # # # # # # # #

0.06 0.4 0.5 0.5 0.6 0.6 0.5 0.8 14 15 0.8 2.8

# # # # # # # # # # # #

0.04 0.1 0.3 0.2 0.3 0.5 0.4 0.5 8 15 0.8 2.3

# # # # # # # # # # # #

0.03 0.2 0.2 0.3 0.2 0.4 0.4 0.5 20 15 0.7 2.3

# # # # # # # # # # # #

0.05 0.4 0.4 0.4 0.4 0.3 0.3 2.3 16 19 0.9 1.6

# # # # # # # # # # # #

0.06 0.1 0.2 0.1 0.2 0.5 0.4 0.3 18 11 0.7 2.3

Post

# # # # # # # # # # # #

0.07 0.3 0.2 0.3 0.2 0.3 0.3 0.3 19 19 1.1 2.2

# # # # # # # # # # # #

0.04 0.3 0.4 0.3 0.4 0.4 0.3 0.3 14 13 0.9 2.4

Tb ¼ mean body temperature, Tgi ¼ gastrointestinal temperature, Tsk ¼ mean skin temperature, Core-Skin gr. ¼ gradient between core and skin temperature, HR ¼ heart rate, TS ¼ Thermal Sensation, RPE ¼ Rate of Perceived Exertion. No differences were observed in the variables between the pre- and post-test.

heat exposure. We cannot exclude the possibility that a protocol with lower exercise intensity - or even completely passive e and with longer exposure duration to heat extended over more than three days, may have evoked the desired physiological adaptations. This would match the recommendations of Taylor et al. [4]. However, it may currently be more efficient to lower the ambient temperature in dwellings of the elderly, for instance by using HVAC (Heating, Ventilating, Air Conditioning) e systems to reduce heat strain in elderly. One can argue that the exposure to exercise in the heat, in particular of the elderly, may impose a higher health risk than the heat wave. However, the exposure is only limited in duration as opposed to heat waves where the exposure to high temperature extends over several days [2]. This reduces the risk for heat related problems, in particular because the time is too short to dehydrate, as is shown by the weight loss in Table 1 that never exceeded 160 g. Dehydration seriously interferes with thermoregulation [24], which may lead to heat stroke [25] during heat waves. Therefore, the recommendation to drink sufficient amounts of water during a hot period has to be an important part of a preparation program to increase thermal resilience in elderly. For practical reasons, the disposable core temperature capsule was swallowed only 30 min prior to the experiment with warm water. Although many authors generally use longer times, there is no agreement on the magnitude and physiological significance of a possible temperature gradient along the gastrointestinal tract [26]. The physiological variables in Fig. 1 show that Tgi and Tsk followed a similar pattern for the young and elderly subjects. HR however dropped in the elderly during the exercise period because the cycling power had to be turned down. Since maximal heart rate shows a strong decrease with age [27] the elderly subjects had a relatively high cardiac strain as compared to the young subjects. TS was higher in elderly during rest and the start of exercise, but the difference disappeared during the last part of exercise, probably since the external power was reduced. The elderly participants indicated that it was very difficult for them to complete the one hour acclimation program, and therefore prolonging the duration of the exposure should be discouraged. When heat wave prediction becomes increasingly accurate, the period of acclimation can start earlier and take longer than three days, with a higher chance on physiological adaptations. It is, however, better not to wait with initiating a training program until a heat wave warning is broadcasted: fit subjects perform better in

the heat than unfit subjects [28]. For the young subjects a longer exposure could have been possible without adverse effects. The thermal strain during the acclimation procedure may have been too low to cause any adaptations. It is also possible that the physiological adaptations to heat do not occur during the acclimation period, but shortly afterwards. It has recently been shown that the functional adaptations may occur a few days after ending a strenuous acclimation program [29]. In our study we have chosen for elderly female participants since they are the most vulnerable population in heat related mortality [14]. With regard to the younger group, it has been shown that menstrual effects in acclimation are minimal [30] and that contraceptive hormones hardly play a role in acclimation [31]. It is well documented that women are less tolerant to a given imposed heat stress then men; however, if cardiovascular fitness level, body size, and acclimation state are standardized, the differences tend to disappear [30]. Females sweat less than males and acclimation induces less adaptation in sweat rate in females than in males [32]. In line with these observations, we found no changes in sweat rate in our subjects. The elderly subjects lost about 28% less weight during the pre- and post-test than the younger group. This is consistent with the conclusions from Pandolf [13] but in contrast with the findings of Armstrong and Kenney [21]. They observed no differences in heat strain between six males with an average age of 61 years and six males aged about 27 years. However, these subjects were matched for physical fitness, which was not the case in our study. The elderly subjects in our study were considerably less fit than the young group, but able to perform their daily activities as expressed by the DEMMI score. The elderly participants had difficulties in maintaining 50 W cycling power, as expressed by the high RPE scores. A reduced fitness level has been associated with a lower sweat rate [33] and may therefore be partly responsible for the observed differences between the young and old group. The observation in this study that no physiological changes occurred after a 3-day heat acclimation program indicate that future studies should aim at longer periods of heat acclimation or for longer exposures during the day. Since elderly were not capable of maintaining exercise for more than an hour, one may consider to reduce exercise intensity to prolong exposure duration. If changes occur in a modified acclimation program, the program should be translated to a feasible recommendation for elderly with easy-touse progress monitoring.

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5. Conclusion In conclusion, we observed no changes in physiological parameters in elderly and young females after a three day short acclimation program. Elderly could hardly tolerate the combined heat and exercise for an hour. A less intense and consequently longer heat acclimation program may proof to be effective. Acknowledgements The work was supported by the national research programme ‘Knowledge for Climate’, in particular the ‘Climate Proof Cities’consortium. The authors thank the participants for their perseverance and Ries Simons MD, Prof. Dr. Ir. Bert Blocken, Prof. Dr. Nico van Meeteren, Drs. Peter Bosch and statistician Arno Krul for their support. References [1] Albers RAW, Blocken B, Bosch PR. Overview of challenges and achievements in the Climate Proof Cities program. Build Environ; 2014 [in this issue]. [2] Daanen HAM, Heusinkveld B, Van Hove B, Van Riet N. Heat strain in elderly during heat waves in the Netherlands. In: Kounalakis S, Koskolou M, editors. Abstract book XIV International Conference on Environmental Ergonomics; 2011. pp. 168e70. [3] Mackowiak PA, Wasserman SS, Levine MM. A critical appraisal of 98.6 ! F, the upper limit of normal body temperature, and other legacies of Carl Reinhold August Wunderlich. J Am Med Assoc 1992;268:1578e80. [4] Taylor NAS, Cotter JD. Heat adaptation: guidelines for the optimisation of human performance. Int SportMed J 2006;7:33e57. [5] IUPS TC. Glossary of terms for thermal physiology, second edition, revised by the commission for thermal physiology of the international union of physiological sciences (IUPS). Pflugers Arch e Eur J Physiol 1987;410:567e87. [6] Armstrong LE, Maresh CM. The induction and decay of heat acclimatisation in trained athletes. Sports Med 1991;12:302e12. [7] Armstrong LE, Maresh CM. Effects of training, environment, and host factors on the sweating response to exercise. Int J Sports Med 1998;19:S103e5. [8] Garrett AT, Goosens NG, Rehrer NG, Patterson MJ, Cotter JD. Induction and decay of short-term heat acclimation. Eur J Appl Physiol 2009;107:659e70. [9] Garrett AT, Creasy R, Rehrer NJ, Patterson MJ, Cotter JD. Effectiveness of shortterm heat acclimation for highly trained athletes. Eur J Appl Physiol 2012;112: 1827e37. [10] Sunderland C, Morris JG, Nevill ME. A heat acclimation protocol for team sports. Br J Sports Med 2008;42:327e33. [11] Weller AS, Linnane DM, Jonkman AG, Daanen HAM. Quantification of the decay and re-induction of heat acclimation in dry-heat following 12 and 26 days without exposure to heat stress. Eur J Appl Physiol 2007;102:57e66.

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[12] Kenney WL, Munce TA. Aging and human temperature regulation. J Appl Physiol 2003;95:2598e603. [13] Pandolf KB. Aging and human heat tolerance. Exp Aging Res 1997;23:69e105. [14] Kovats RS, Hajat S. Heat stress and public health: a critical review. Annu Rev Public Health 2008;29:41e55. [15] Bouchama A, Dehbi M, Mohamed G, Matthies F, Shoukri M, Menne B. Prognostic factors in heat wave-related deaths: a meta-analysis. Arch Intern Med 2007;167:2170e6. [16] Stafoggia M, Forastiere F, Agostini D, Biggeri A, Bisanti L, Cadum E, et al. Vulnerability to heat-related mortality: a multicity, population-based, casecrossover analysis. Epidemiology 2006;17:315e23. [17] Short CA, Lomas KJ, Woods A. Design strategy for low-energy ventilation and cooling within an urban heat island. Build Res Inf 2004;32:187e206. [18] Dubois D, Dubois EF. A formula to estimate the approximate surface area if height and weight be known. Arch Intern Med 1916;17:863e71. [19] De Morton NA, Davidson M, Keating JL. The de Morton Mobility Index (DEMMI): an essential health index for an ageing world. Health Qual Life Outcomes 2008;6. [20] ISO 9886. Ergonomics e evaluation of thermal strain by physiological measurements. Geneva: International Organization for Standardization; 2004. [21] Armstrong CG, Kenney WL. Effects of age and acclimation on responses to passive heat exposure. J Appl Physiol 1993;75:2162e7. [22] Borg G. Perceived exertion as an indicator of somatic stress. Scand J Rehabil Med 1970;2:92e8. [23] StatSoft I. STATISTICA (data analysis software system). version 8 0, www. statsoft.com; 2008. [24] Sawka MN, Young AJ, Latzka WA, Neufer PD, Quigley MD, Pandolf KB. Human tolerance to heat strain during exercise: influence of hydration. J Appl Physiol 1992;73:368e75. [25] Bouchama A, Knochel JP. Medical progress: heat stroke. N Engl J Med 2002;346:1978e88. [26] Byrne C, Lim CL. The ingestible telemetric body core temperature sensor: a review of validity and exercise applications. Br J Sports Med 2007;41:126e33. [27] Gellish RL, Goslin BR, Olson RE, McDonald A, Russi GD, Moudgil VK. Longitudinal modeling of the relationship between age and maximal heart rate. Med Sci Sports Exerc 2007;39:822e9. [28] Aoyagi Y, McLellan TM, Shephard RJ. Interactions of physical training and heat acclimation. The thermophysiology of exercising in a hot climate. Sports Med 1997;23:173e210. [29] Daanen HAM, Jonkman AG, Layden JD, Linnane DM, Weller AS. Optimising the acquisition and retention of heat acclimation. Int J Sports Med 2011;32: 822e8. [30] Kenney WL. A review of comparative responses of men and women to heat stress. Environ Res 1985;37:1e11. [31] Armstrong LE, Maresh CM, Keith NR, Elliott TA, VanHeest JL, Scheett TP, et al. Heat acclimation and physical training adaptations of young women using different contraceptive hormones. Am J Physiol Endocrinol Metab 2005;288: E868e75. [32] Buono MJ, Leichliter Martha S, Heaney JH. Peripheral sweat gland function, but not whole-body sweat rate, increases in women following humid heat acclimation. J Therm Biol 2010;35:134e7. [33] Buono MJ, Sjoholm NT. Effect of physical training on peripheral sweat production. J Appl Physiol 1988;65:811e4.

Please cite this article in press as: Daanen HAM, Herweijer JA, Effectiveness of an indoor preparation program to increase thermal resilience in elderly for heat waves, Building and Environment (2014), http://dx.doi.org/10.1016/j.buildenv.2014.04.010

Hein Daanen, paper drie dagen acclimatisatie aan hitte bij oudere vrouwen  

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