Environmental Health Perspectives<\/em>. But even the residents of Mecca have physiological limits, the team found in another study: Their mortality numbers started skyrocketing above 38\u00b0.<\/p>\nIn general, such differences at the population level could be due to many factors, Bouchama says, including access to air conditioning, outdoor conditions and possibly even genetic factors. But physiological acclimation probably also plays a role, he says.<\/p>\n
In regions with distinct warm and cold seasons, there\u2019s some evidence that young adults can acclimate over summer, exhibiting slightly higher sweat rates and lower skin temperatures at the end of the season versus the beginning.<\/p>\n
But the reverse can also happen, molecular biologist Elaine Lee of the University of Connecticut in Storrs and colleagues have found. The team\u2019s unpublished study of several dozen athletes suggests that it takes them longer to acclimate in the late winter compared with early winter, hinting that they lose their summer adaptations over the cold season.<\/p>\n
Some scientists have posited that acclimation is why early summer heat waves are often deadlier than ones later in the summer. Because people undergoing heat acclimation protocols typically lose their adaptations within weeks, Gagnon suspects they would similarly lose any acclimation benefits in the cooler periods between heat waves.<\/p>\n
\u201cWe know for sure that the body can acclimate, but we have to be exposed to heat on a regular basis,\u201d Gagnon says. \u201cIt has to be a pretty considerable dose.\u201d<\/p>\n
Finding the right dose<\/h2>\n
The science of heat adaptation in young, healthy people is well-established. But what about older individuals or those with chronic health conditions? Scientists have long known, for example, that the ability to effectively sweat and vasodilate declines with age.<\/p>\n
New research suggests that intentional heat acclimation can boost these responses just as effectively in older adults as in younger people. Gagnon and colleagues asked 15 adults in their 20s and 30s and 16 adults in their 60s and 70s to immerse themselves in 40\u00b0 water for an hour and then spend the next hour alternating between shoulder-high and waist-high water levels to ensure their body temperature stayed at or above 38.5\u00b0.<\/p>\n
After repeating this process for seven days, both groups started to sweat and vasodilate earlier upon heat exposure. They also experienced a 0.4\u00b0 lower body temperature, on average, than they did at the beginning of the experiment. The scientists also observed a five-beats-per-minute lower heart rate, on average, in both groups by the end of the protocol, they reported in May in the Journal of Physiology<\/em>.<\/p>\nThe upshot of the study, Gagnon says, \u201cis that even if we\u2019re older, our body still has the ability to adapt to heat.\u201d<\/p>\n
That idea led some of the women in Li-Maloney\u2019s study to take part, hoping the experience would brace them for summer heat waves. \u201cThey love the idea that a study like this might make them at least feel better when summer starts,\u201d she says.<\/p>\n
To find out, Li-Maloney\u2019s team had the women endure an artificial heat wave before and after the experiment. Volunteers spent an hour sitting in a room set to 36\u00b0 and 45 percent humidity. \u201cIt sucks, I\u2019m not going to lie,\u201d Li-Maloney says.<\/p>\n
The team saw a significant difference in participants\u2019 physiology during the second artificial heat wave. After the acclimation period, the women maintained a 0.2\u00b0 lower core temperature and a several beats-per-minute lower heart rate than before the acclimation period, the researchers reported in April at the American Physiology Summit in Minneapolis. The team was particularly struck by how long the women avoided hitting the peak body temperatures they had reached during the first heat wave.<\/p>\n
What\u2019s still unclear is whether this translates to meaningful reductions in heat-related illness. Scientists will have to deeply consider the safety of such protocols, especially for people with heart disease, mobility issues or cognitive impairment. \u201cIf they were ever left to do it by themselves outside of a laboratory environment, are they potentially at risk?\u201d asks physiologist Jessica Mee of the University of Worcester in England.<\/p>\n
But with further study, hot water immersion could one day be a viable strategy to prepare vulnerable populations for the extreme heat of summer months\u2005\u2014\u2005and a safer alternative to other proven acclimation methods like hot yoga or walking or running at hot temperatures, Li-Maloney says. \u201cBy the time the first heat wave hits, you should be more protected.\u201d Some participants in the study are already convinced. One woman traveled to Thailand, exploring its sweltering capital in heat often in excess of 30\u00b0. \u201c\u2018Everyone [else in] my tour group was suffering,\u2019\u201d Li-Maloney recalls the woman telling her, \u201c\u2018and I felt great.\u2019\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"
\u201cI can\u2019t do this,\u201d the woman in her 60s said as she lowered herself into the 40\u00b0 Celsius water that filled a big silver tub at the end of a dimly lit room in the University of Ottawa\u2019s Human and Environmental Physiology Research Unit. It was only after the temperature dropped a degree that she […]<\/p>\n","protected":false},"author":1,"featured_media":105916,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[10],"tags":[],"_links":{"self":[{"href":"https:\/\/www.adviews.info\/news\/index.php?rest_route=\/wp\/v2\/posts\/105915"}],"collection":[{"href":"https:\/\/www.adviews.info\/news\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.adviews.info\/news\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.adviews.info\/news\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.adviews.info\/news\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=105915"}],"version-history":[{"count":0,"href":"https:\/\/www.adviews.info\/news\/index.php?rest_route=\/wp\/v2\/posts\/105915\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.adviews.info\/news\/index.php?rest_route=\/wp\/v2\/media\/105916"}],"wp:attachment":[{"href":"https:\/\/www.adviews.info\/news\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=105915"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.adviews.info\/news\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=105915"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.adviews.info\/news\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=105915"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}