welcome back part of our special topic unit is talking about Thermo regulation and how do we maintain body temperature not only just at a resting state but also during exercise you'll notice as we go through the special topics unit that this is all information that isn't typically falling into one of our other units being bioenergetics neuromuscular or cardiorespiratory so this lecture here is going to talk about regulation of body temperature some of the adaptations that we see and some of the things that happen while we're in ex exercise State as well as some exercise precautions that we have to think about when it comes to our Thermo regulatory response so when we talk about Thermo regulation and exercise one we're going to talk about how do we regulate our body temperature what is our response in a heat environment where uh the ambient temperature is elevated and also relative humidity and then how do we adapt to it so when we talk about the environmental adaptations this is referred to as acclamation and a climatization that we'll get to later on when it comes to our regulation of body temperature we always try and maintain a constant internal body temperature as relatively constant as as possible we don't want to see a big spike in body temperature because that's when we get up close to what's known as a critical body temperature threshold but we also don't want to drop body temperature internally either so normal range of body temperature ranges somewhere between 97 and 100° fah on average we generally hear people say that normal body temperature is about 98.6 Fahrenheit on average however what we're actually seeing over the last several decades is that body temperature on average is dropping a little bit so now we see that the normal average body temperature is even below that closer to 98 degrees or maybe even 97 8 degrees think about why that may be true we could go into a whole lecture and dive into details about the climate and how everything's changing and all of those factors but a big influential reason behind the drop in average body temperature is because of a drop in lean mass so when we talk about body composition in that lecture we'll see that lean mass is an active tissue so because as a PO ation we're carrying more fat mass in the body which is an inactive tissue and less lean mass lean mass is what's responsible for actually creating metabolism so as you burn energy that produces heat so since we have less lean mass we're producing less heat inside the body our internal body temperature reflects the balance between heat production and heat loss so there's a scale here or a balance to where we have have to make sure that we're giving off the heat that we're producing because we don't want to store that internally because it can have a lot of detrimental effects from a physiological standpoint so that's what creates as as what we know as homeotherms in other words we have this internal mechanism that allows us to be able to produce heat give off heat and reduce heat so that we can maintain that balance in some form or fashion so this is the balance here that we're talking about you see this uh predicted here is a balance scale where we have heat gain and we can gain Heat by either metabolic heat so maybe that's through metabolism maybe that's through muscle contraction or in a cold stress that could be something like shivering but we can also gain heat from the environment as well now heat loss has to be able to maintain all of that heat gain and keep everything and check and we can lose heat by way of radiation by way of conduction convection and evaporation so let's look at each one of these individually so what is conduction conduction occurs when you have a direct molecular contact with another object so if you've ever been to maybe a sporting event or maybe the first day a class you walk in you know in the fall and we're in August it's hot we're in South Miss Mississippi so your body temperature is a little bit elevated you walk into a classroom um and it's cold in the classroom or it's at least cool hopefully and you sit down in the chair when you sit down in the chair that chair is actually equivalent or should be equivalent to the temperature of the room so that's cooler than your body temperature so when you sit down in the chair and you feel like wow this chair is a little bit cold you're going to lose some of your body heat Heat's going to go from high to low so you're going to lose some of your body heat by way of conduction direct contact from your body to the chair convection here is when you have a gas or a liquid that moves across the surface of the skin so think of it this way if if I go outside and it's cold outside and the wind's blowing I'm going to lose more of my body heat to the environment because my skin temperature is higher than the ambient temperature outside so as the wind blow blows across the surface of my skin I'm going to lose some temperature to that air around around me then you have radiation so radiation is the transfer of heat by infrared Rays that's happening all the time so we gain heat from the environment by UV rays we uh can lose heat to the environment if the environmental temperature is lower than our body temperature have you ever been sitting next to somebody close enough to where you can actually feel their body heat from that person that's radiative body heat losss so they're losing Heat by way of radiation and you're feeling that heat by way of infrared Rays um at a resting state the body loses about 60% of its excess Heat by way of radiation so the last one here is evaporation evaporation we lose a little bit of body heat through evaporation at a resting state but primarily it's going to be radiation evaporation only counts for about 25% at rest and we'll talk more about evaporation in just a minute we want to be able to regulate these modes of heat transfer because we want to avoid both of these situations here either hyperthermia where body temperature is elevated or hypo thermia where we have a decrease in our body temperature so look at the one through three here and compare that that to uh the mode of heat transfer number four right here how is one through three different from four so with evaporation we have to have fluid present because it creates a vapor pressure gradient so that we lose heat to the environment so the important characteristics of one through three that make it different than four are one through three can be dry heat exchange where is number four is only considered a wet heat exchange because fluid has to be present for evaporation to occur we'll talk in a little bit more about evaporation this is when heat is transferred from the body so say we build up an internal body temperature and we move that body heat towards the surface of the skin as we get it to the surface of the skin we start to sweat so that sweat's going to come from our plasma volume when enough heat is gained at the surface of the Skin So when enough of our body temperature moves to the surface of the skin it converts that sweat into a water vapor which essentially is gas at that point once it becomes a water vapor pressure as long as the vapor pressure on the surface of my skin is greater than the vapor pressure of the environment I'm going to move from an area of high pressure to low pressure so my vapor pressure is going to move or my water vapor is going to move from the surface of the skin to the environment and I'm going to lose that heat so evaporation accounts for about 80% of the heat loss during exercise so it's a major mechanism of heat loss when we start to move the body and produce heat remember going all the way back to bioenergetic 60% of the energy that you burn is given off as heat so think about when I start to do my muscle contractions how much heat I'm producing and I have to be able to dissipate that heat I can't let it build up internally it only accounts for about 25% at rest like we said earlier but you also have something known as insensible water loss so this is water loss or evaporation that happens when you don't realize that it's happening so it's unrecognizable and this is really coming from the lungs and the during the breathing process remember from our unit fre material that when you take a breath in that air by the time it gets all the way down to the respiratory zone where gas exchange occurs it's fully saturated with water so one of the primary um jobs of your respiratory track is to humidify that air as it moves deeper down towards the alvioli so that also happens when we exhale when you exhale because that air is so humid you're losing some of your body water content through the breathing process that accounts for about 10% of your heat lws uh throughout the day and talking more about evaporation the rate of evaporation of the uh sweat from your skin is dependent on three factors so the convective currents around your body so is water or air moving across the surface of the skin how much of your skin is exposed to that open air in the environment and and this one right here is a big factor what's the temperature of the ambient air in the environment and what is the relative humidity so relative humidity plays a major role in our evaporative process and being able to dissipate body heat as it's building up inside the body so what is humidity humidity is the water vapor content or the water vapor pressure in the air around us plays a major role in the amount of heat we can lose through the evaporative process so you'll always see when you look at you know the weather forecast the ambient temperature so say today it's supposed to be 92 degrees outside but also look at the relative humidity because relative humidity can have a great effect not just in your uh your physical process of evaporation but also your perception of the heat outside so think of reasons why does relative humidity place such an important role in your perception of a heat stress so when we talk about relative humidity it when you have a high relative humidity outside there's a reduction in the pressure gradient between your skin and the external environment so remember for something to move through a gradient it moves from an area of high pressure to low pressure so this is why humidity plays such an important role in my thermal stress and my regulation of my body heat is because if say I create a vapor pressure on my skin and then I go outside and I'm sweating and the relative humidity the vapor pressure of the air around me is high there's not as much of a difference between the vapor pressure of my skin and the vapor pressure in the air so that gradient between the two is reduced so I don't have as much pressure forcing that uh water vapor or that sweat to move from my skin to the environment so it's harder for me to lose that body heat you'll notice during the summertime when it's high heat and high relative humidity that a lot of your sweat rolls off of your skin have you ever been sweating and you stand still for a minute or you sit down on a chair or something and there's a little bit of a pool of sweat around you wherever you were standing or wherever you were sitting you feel the sweat just kind of rolling down your face on your forehead your arm whatever it is that's because relative humidity is high and we're not creating a gradient that's great enough to force that sweat to go to the environment around us so therefore it limits our evaporation capabilities and sweating doesn't actually dissipate as much body heat as it should it says here like we've been talking about the VAP vapor pressure on the skin must be greater than the vapor pressure in the air if we want that heat to leave the skin and go to the environment around us so what circumstances could you think of that temperature and humidity would play a drastic effect in our ability to therm regulate think about maybe if you go to Phoenix Arizona where it's a dry heat so it's a high uh ambient temperature but it's a low relative humidity what would be your concern in that environment remember it's all about the vapor pressure gradient so in that environment I may be able to evaporate my body heat so quickly that I don't realize how much I'm actually sweating because I have a low relative humidity there's a big gradient between my skin and the ambient environment so that vapor pressure leaves my skin at such a quick rate that I'm not not recognizing how much I'm sweating so a major concern here would be dehydration you can get dehydrated very quickly in a high temperature low humidity in other words a dry heat because you don't realize how much you're sweating at that State now think of the opposite end of the spectrum look we typically experience in south Mississippi down here with a high heat and a high humidity what would be your concern there at that point I'm still concerned with dehydration but the reason for that is because evaporation isn't working as effectively as possible because I have high humidity meaning I have high vapor pressure in the air and I'm trying to create enough vapor pressure on my skin to be able to evaporate my heat and dissipate that heat to lower my body temperature back down so I avoid that high temperature critical threshold so what ends up happening is a lot of times like we were saying earlier you feel that sweat rolling off of your skin the body's response is I'm not evaporation is not working like it's supposed to I'm not getting rid of the body heat like I need to so I'm going to sweat more and you're going to sweat more and more at that point I'm losing a lot of the plasma volume from my blood my blood's going to get really thick in other words viscosity of my blood is going to go up so at that point I'm also concerned with dehydration as well but I'm also concerned with a cardiovascular stress in addition to the dehydration because my blood viscosity is high so when we come to internal body temperature your core temperature at rest like we said on average most people say 98.6 degrees fahit but notice skin temperature at rest is lower than your core temperature that's good that creates a gradient that creates a difference between the core and the skin everything's going to move from an area of high to low and that's what allows us to move that high temperature inside our body towards the skin and let it go to the environment so that we can maintain everything relatively constant during exercise you can see core temperature go up to about 104 degrees fahr uh you may even see the temperature in the active muscle tissue the muscle that's primarily moving the body during exercise go up to almost 108 degrees F so extreme temperatures within the muscle tissue itself this is very important right here that your core temperature above 40° C which is 104 degrees Fahrenheit can affect the nervous system and that can reduce the ability to get rid of that body heat that you're producing so this is what we call let's see let's draw it right here here 104° fah is what we call the critical temperature threshold this is why their clinical recommendation is you know if you've ever been to the doctor and you feel sick and you're like oh they take your temperature it's 101 or 102 they're like yeah it's a high temperature but you just need to take some Tylenol or some ibuprofen stay calm stay relaxed and all of that stuff let's break that temperature and get it to come back down but if your temperature gets up there at or close to 104° F that's usually in more of an emergency situation because once you reach that critical temperature threshold we start to see degradation of proteins within the body and go back to everything that we've talked about this semester and think about how many things are made of proteins so enzymes are made of proteins if your enzyme start to break down then that's going to regulate or uh disrupt your metabolism um um other things that are made of proteins receptors are made of proteins so if those start to break down we can't respond to the hormones or the neurotransmitters or whatever it is that's trying to bind to that receptor site other things may be the myin remember myin around your neurons is made of a lipid protein so if that starts to break down then that influences and has an effect on our ability to send a signal through the body through air eent neurons so a lot of things can happen if your body temperature gets too high up there at or close to or even above 104° fah now on the opposite end of the spectrum if we look at below 34 degrees C or 93.2 degrees fahit we can see that we start to have an effect on your cardiac tissue so you could see abnormal cardiac function where your heart starts to flutter you maybe get fib cation and these sporadic signals that are being sent from your saay node or the impulses start to get ectopic beats out in your ventricular cells and that can cause a disruption in the way that the heart's supposed to function so any of the heat that's produced that's not given off means that we're going to end up storing it inside the body so we have to make sure that our Thermo regulatory capacity is being or is functioning the way that it should so that we can regulate body temperature where does a our regulation of body temperature come from this is your body's thermostat right here is the hypothalamus you'll see in just a second we have a specific area of the hypothalamus known as the P ah that it responds to all the input from Thermo receptors out in the body so we have Central Thermo receptors and we have peripheral Thermo receptors Central are located in the hypothal and they monitor the temperature of the blood as it's coming through the brain peripheral Thermo receptors are located out in the skin and they monitor the temperature out in the periphery and the ambient temperature of the environment that you're in so all of this information about temperature is sensed by Thermo receptors and it sends it back to the hypothalamus and a specific area known as the pah of the hypothalamus interprets that information in creates the appropriate response whether that's okay we're building up too much temperature inside so I need to start sweating so that I can get rid of this body heat or my body temperature is starting to drop a little bit one of the responses that may come from that is I'm going to start to get these little quick muscle contractions known as shivering because a muscle contraction is going to burn energy 60% of the energy you burn is giving off is heat so that's your body's way of trying to build its heat back up so that pah stands for pre-optic anterior hypothalamus it's a very specific area of the hypothalamus that responds to changes in temperature we're actually more sensitive to an increase in temperature as compared to a decrease in temperature we don't want that core temperature that internal body temperature to go up because once it starts to go up like we said earlier the closer you get to 104° fah that's when we start to see changes and disruptions in our protein structures so depending on what your your stress is whether that's heat or versus a cold stress you're going to have a different response and that response is being initiated by the preoptic anterior hypothalamus so four primary effectors that can happen sweat G sweat glands can be stimulated so we'll start to secrete sweat and create that vapor pressure so that we can evaporate that heat and get it out of the body and into the environment we're going to see that the smooth muscle around the arterials plays a major role in our ability to regulate body heat one of the things that we'll do say we go into a heat stress what we'll end up doing is constricting the blood vessels in the core dilating the blood vessels in the skin so that we shunt blood from the core to the SK skin force it to go to the skin and that body and that blood is carrying our body temperature and that's our way of moving it to the skin so that we can get rid of it and on the other side of this if we go into a cold environment we'll constrict blood vessels on the skin dilate them in the core so that we can move that warm blood that temperature back to the core and protect our vital organs skeletal muscles play a role here so when we talk about shivering shivering is creating heat so that allows us to gain heat if we're in a cold environment and then the endocrine glands so specific hormones can be released to help in the regulation of body temperature say I'm in a cold environment I may release things like catacol amines to try and stimulate my metabolism and if my metabolism goes up I'm going to burn more energy burn more energy I'm going to produce more heat so that helps me to bring my temperature back up so when we look at the thermo regulatory response we can see in this case where we have an increased blood and internal temperature what that does is that signals to the hypothalamus for us to vasod dilate at the level of the skin so that we can move uh that warm blood and that body temperature from the internal environment towards the skin sweat glands become activated at that point and we go through evaporation so that we can lose that body heat evaporation allows us to bring our body temperature back down and once it's back down within normal acceptable ranges this whole system this whole sequence of events is shut off so if we're decreasing uh This original stimulus that created a response what is that known as remember this is known as negative feedback so this is an example of a negative feedback loop that allows us to be able to regulate our body temperature here now our cardiovascular response to exercise is drastic especially when we have exercise in a hot and or humid environment so we know one exercise is going to increase our body temperature so when it comes to the heat environment or high heat environment this has a major effect because cardiovascular system plays such a role in the dissipation of body heat that when you have have active muscles that are requiring more of that oxygenated blood because they're exercising and then we're in a heated environment the skin has to have the oxygenated blood being sent to it so we can dissipate that body heat now we've actually created a competition between the exercising muscle and the skin on where is the blood going to go this could create a limitation to Performance especially when we're talking about this from a thermo regulatory uh perspective is because my active tissue is saying look I need you to vasodilate down here in the muscles because I need that blood to be able to continue to exercise but my body is saying hey you're building up all this body temperature I need to dilate in my skin dilate the blood vessels in my skin so that I can get rid of all this body temperature so the battle between these two uh can limit your performance because because we don't have as much blood that can go to the exercising tissue to supply that exercise demand so what changes here in a hot humid environment when it comes to stroke volume we're going to see that we get a decrease in our stroke volume several reasons for that is because one we're sending more blood to the skin to dissipate that body heat but also because we're sending uh blood to the skin that means that we're going to be sweating if we're sweating the sweat comes from the plasma volume if we lose plasma volume we're losing quote unquote the water content the dilution of our blood and that's making our blood more thick because it's thicker it's harder to pump so what is stroke volume stroke volume is the amount of blood ejected by the left ventricle or by The ventricle with every contraction so now we have less blood coming back to the uh heart to be sent out with each contraction and the blood is thicker it's harder to pump so stroke volume is going to go down what happens in turn is heart rate's going to go up the only reason for that is because we want to maintain let's say we want to maintain cardiac output so cardiac output remember is made up of stroke volume times heart rate so if stroke volume is grow going down for me to be able to maintain card back output I have to compensate for the drop in stroke volume by increasing my heart rate so you'll notice in exercise in a hot and human environment that I'm going to get a drastic increase in my heart rate because I'm trying to compensate for that drop in stroke volume overall answer the question here what does this do to our performance capabilities potentially it limits our uh our performance because heart rate can only increase to a certain extent we don't have this in definite capacity to continue to increase heart rate with that drop in stroke volume so exercise can only be maintained at a certain level of intensity as long as we can maintain a uh a certain heart rate that we can keep up with to be able to get to steady state once we get to a point where we can't maintain steady state anymore we have to switch back to anob metabolism go all the way back and tie it all together once you switch back back to anerobic metabolism this leads to an increase in things like hydrogen and an increase in CO2 which overall drops your pH towards the acidic environment and we know what acidity is going to do to things like our enzymes and other structures that are related to proteins in that localized environment and when it comes to our body fluids um and exercise in a hot humid environment one as ambient temperature exceeds skin skin temperature in other words as the temperature outside is greater than the temperature of the skin we're actually going to gain heat from the environment into the body remember everything's moving from an area of high to low so higher temperature outside than my skin temperature conduction convection and radiation are going to result in me gaining heat from the environment this is why in evaporation becomes incredibly important because I have to dissipate that body heat I don't want to gain it I don't want to store it so I need to be able to get rid of it so in that hot humid environment when I'm gaining heat from the environment the hypothalamus is going to increase my sweat rate on average normally you're going to lose about one liter per hour uh per square meter of body surface area when it comes to your sweat rate that's about two to three% of your body weight every hour so we have a significant effect when it comes to the risk of dehydration here the reason we see uh or what we see because of an increase in sweat rate is blood volume decreases because uh we're reducing plasma volume and in our sweat if you've ever had sweat rolled down your face and it gets to the side of your mouth and you happen to taste it you know that sweat tastes salty that's because it has a high sodium content in it so sodium is one of these electrolytes that you're going to lose in sweat which can play a role in things like muscle contraction and all of that stuff and then um when you start to sweat and your blood volume drops and your electrolytes drop and all of those things we're going to end up releasing something known as aldosterone and also something known as ADH which antidiuretic hormone and those lead to water reabsorption in the kidneys and sodium retention in the kidneys we're going to talk more about this on the very last slide of this lecture but these are all things that um come from an incre increase in sweat rate so when it comes to excessive heat gain there's serious health threats that we have to be aware of of but when we're talking about exercising uh in a hot humid environment it's not just the temperature that we have to be aware of so yeah we have to be aware of the temperature here but we also have to think about the humidity is it a saturated environment versus a dry heat what's the air velocity like is there a wind blow is there a breeze or is it just a still stagnant air in the environment and then what's the amount of thermal radiation when you look up in the sky do you see that there's cloud cover or there trees blocking uh pre preventing a or allowing creating a barrier between you and the UV rays so we have to be aware of that you also have to be aware of what your ground contact like so in a hot humid environment we want to try and avoid exercise on things like asphalt and concrete because those have a very high absorption rate of the the thermal heat thermal radiation so when your foot hits it that heat can actually come up from the ground through the sole of your shoe and into your foot and cause you to absorb heat that way so we have to be aware of all these different factors when it comes to exercise now talking about dehydration this is when we get a decrease in the total body water content it occurs at a much faster rate than you think it does especially in a hot Andor humid environment so remember earlier we said back here that we lose about one liter per hour per square meter of body surface area when we're in the hot and humid environment that can increase to up to 2 to three lers per hour we start to see dehydration has an effect on the body a negative effect when we get to a weight reduction of about 2% of your total body weight uh coming from fluid loss so as an example right here we have a 70 kg male 2% of that body weight is about 1.4 kgs which is about the equivalent of 1.4 lers of fluid loss coming from sweat put that into perspective if we're right here in this range right here and say our sweat rate is 2.4 lers per hour um of fluid loss during the exercise then that 1.4 is about 50% of that so so we can see that we would see dehydration and negative effects in as little as 30 minutes of exercise in a hot humid environment then when you get to that dehydration State that's going to lead to hypothermia where we have an increase in our core temperature and that can create all kinds of effects and cardiovascular stress on side or inside the body and on all the different mechanisms like your metabolism this right here is a very important statement to remember when you're especially in a hot humid environment you cannot rely on The Thirst mechanism to be able to recognize that you need to take in fluids the reason for that is a thirst mechanism this happens we'll write it right here thirst mechanism happens at uh approximately 2% reduction and body weight coming from fluid loss so at that State you're already dehydrated when The Thirst mechanism kicks in so we have to make sure that we're taking in fluids from the onset of exercise about every 10 15 20 minutes we're taking fluids in so that we avoid The Thirst mechanism kicking in because like we said by the time you recognize you're thirsty you're already dehydrated so here's a um your heat disorders with increasing severity as we move from left to right here so starting with heat cramps heat cramps are just signified by these muscle cramps that are happening and this is goes all the way back to something that we talked about in the neuromuscular unit when we covered um the theories of exercise induced muscle cramps remember one of those theories was the electrolyte dehydration Theory so when you start to get dehydrated did you lose those electrolytes one of those electrolytes being sodium which causes an imbalance in sodium and potassium on your membranes well that disrupts your membrane potential so that could be a reason that we're getting muscle cramps here as we increase in our severity if you don't recognize this and continue to exercise you'll see here The Thirst mechanism is already um or is activated once you're already in the stages of heat illness we'll start to see profuse sweating and fatig here by the time you get the heat exhaustion we're going to see muscle weakness and then you can experience pale and cool skin why is that why if we're sweating a lot why we had this profuse sweating right here why would we get pale and cool skin if we don't recognize that profuse sweating and allow things to continue one we're going to get cool skin because sweating is doing its job convection currents are moving around the body and all of that but at this stage right here we'll have cool skin because we're we're getting rid of our body heat through the sweat mechanism but it's also going to be pale because your body's starting to recognize that I got to I got to protect my V vital organs so I'm going to start to go into survival mode and shunt blood redistribute blood back to my core so now uh this the oxidated blood is is moving away from the surface of the skin and back to the core and it gives you a little bit of that pale orientation move on and increase in severity towards the heat stroke we'll see that we get headaches and nausea chills and goosebumps when you get to closer to a heat stroke you'll actually see that you have a sensation of sweating or in other words you stop sweating that's because we're shunting blood back towards the core so we're can constrict the blood vessels in the skin and dilate the blood vessels around our vital organs as protective mechanism and then when you get the heat stroke you'll see a strong and Rapid pulse hot and dry skin and then confusion so let's talk about each one of these real quick when we talk about strong and Rapid pulse right here why would you see that with a heat stroke think about what's happened at this stage so we've stopped sweating and the reason for that is because we need to move blood back to your vital organs and we've been been sweating so much that our blood is very thick so the strong pulse is going to come because you have a high viscosity in your blood so the ventricles have to contract really hard to pump that thick blood and we have a rapid pulse because we're trying to compensate for it to make sure that even though I'm protecting my vital organs and my blood's really thick I've still got to send that oxygenated blood out to my systemic circuit to supply my physiological demand why do we see hot and dry skin the reason for that is remember I've stopped sweating and I've moved blood back towards the surf or back towards my internal environment so the reason I get hot skin is because I'm gaining heat from the ambient environment at that point so I'm the hot environment higher temperature than my skin temperature I'm starting to gain heat from it dry skin is because I've stopped sweating so I don't have that water vapor that's coming to the surface of my skin and allowing me to dissipate that body heat so recommendations here to try and prevent hypothermia I want to avoid exercise in a hot humid environment if possible and one way to do that is to schedule practices or events competitions whatever the case is early in the morning or later in the evening closer to nighttime where we have those lower temperatures and lower relative humidity if I'm exercising during the day I want to wear light weight clothing light colored clothing because remember the darker the clothing the more uh radi heat it's going to gain and absorb and lightly or Loosely woven clothing so that I can allow a little bit of convective currents to come through and I kind of get that moisture wicking property that happens Exposed Skin if possible because I want convective currents and conductive uh and conduction to happen so that I can lose body heat as effectively and efficiently as possible drink plenty of fluids so I'm matching my sweat rate now it's hard for us determine to what is your actual sweat rate so that we know how much to drink to be able to match that so General recommendation is to take in fluids every 10 to 20 minutes I want to take in about 12 ounces of fluid when I do that now whether there's a lot of research out there on whether to take in you know uh room temperature fluids or cold temper tempure or warm fluids or so on it's really kind of a personal preference um on what temperature the fluid is but you want to make sure that you're taking it in to every 10 to 20 minutes to give your body enough time to be able to absorb it get it into our blood so that we keep our plasma volume elevated and we don't see all the effects that we've been talking about so far and definitely right here know your symptoms of heat stress so go back right here know these things front back and side side to side so you can recognize when there's a warning sign of a heat stress in exercise in those environments now what happens if you go exercise in one of these environments is your body's going to adapt to it so let's say you take somebody from Denver Colorado or Phoenix Arizona and you bring them down here to Hattisburg Mississippi so we're in a hot humid environment you take somebody that's not used to that you'll notice when they get down here especially when they're exercising that they're going to sweat more and their body temperature is going to go up very quickly during exercise but over the next couple of days or maybe even weeks we'll start to go through the phases of acclamation and a climatization so these are physiological adaptations that occur that improve our ability in dissipating that internal body heat in turn we get an improvement in our work capacity and it reduces the amount of stress that you place on per se your cardiovascular system or your respiratory system what are the things that change we're going to see that sweating occurs earlier in exercise so if we have a pre and post State here let's say that at rest our body temperature is 98.6 de F on both so at rest 98 8.6 de F you bring somebody from Denver Colorado where it's a little bit more of a cooler uh lower humidity environment they come down to Hattisburg uh Mississippi they're going to start sweating let's just these are just theoretical numbers they're going to start sweating when their body temperature gets to 101 degrees fah now we do this for the next say two three weeks and have them exercise in this hot humid environment maybe they start sweating at let's say 99.5 de F because they're sweating earlier in exercise what that allows me to do is I can maintain a lower core temperature throughout the duration of the exercise session and that allows me to be able to not sweat as much because I'm not sweating as much I don't lose as much of my plasma volume and since I'm not losing as much of my plasma volume my blood doesn't get thick since my blood doesn't get thick then my heart rate doesn't have to be as high to compensate for that drop and and stroke volume so all of these are tied together because of this Factor right here that I start sweating earlier at a lower body temperature in other words I drop my sweat threshold so we can write that here I drop my sweat threshold to a lower temperature and that allows me to maintain a lower core temperature throughout the duration of the exercise throughout the day and everything else and that places way less strain on my cardiovascular system I'm also going to decrease my secretion of inflammatory markers so we have all these different things within the body that are biomarkers that allow or that create inflammation because of the physiological stress inside the body so because I'm creating less stress in the body I have a decrease in inflammation that's present how long does it take to get acclimated let's say it's on average about 10 to 14 days so roughly around two weeks if you're exercising about an hour every day and that exercise needs to be at least moderate intensity now this can be different ult from some for somebody if you take them from an environment where they're not used to heat and humidity and bring them to this environment and ask them to exercise for an hour every day at above 50% of their Max Capacity so what I can do to help with that and to combat that is use interval training so by doing interval training I can exercise at a higher workload say a higher intensity and accumulate more volume of exercise by going into a high-intensity exercise and then take a rest and then back to high intensity take a rest back to high intensity that allows me to exercise above moderate intensity and my whole goal is to accumulate an hour or two hours worth of exercise so that I can go through that acclamation process now difference between acclimation and acclimatization acclimatization is the longterm effect so this is actually what's going to happen over months or even years when you take somebody and just completely move them from say Denver Colorado to Hattisburg Mississippi and they live here on while they're living here they become acclimatized to that environment to the new environment that we're in so when we talk about why do the why are these adaptations important is because fatigue is going to start to happen happen when we reach that critical temperature threshold remember that's 40° CS or 104° F so what I want to do is I want to sweat earlier maintain a lower core temperature throughout my exercise session so that it don't allow the body to get closer to that critical temperature threshold when the body gets there during exercise it starts to protect itself so you go into this kind of protective mechanism to prevent yourself from from overheating and creating uh negative effects like the breakdown of proteins and all those things we said earlier so because of that remember fatigue is the inability to maintain the required or expected amount of force to be able to continue the exercise so if my body goes into this state where it's protecting itself it's going to slow everything down and because of that I can't maintain the force requirement to continue the exercise which is known as fatigue so by maintaining a lower core temperature because I've become acclimated to it I reduce the amount of fatigue that is felt from that heat stress so it allows the tolerance of longer duration exercise and higher intensity exercise in that hot humid environment now the last thing here is talking very briefly about hormones and fluid balance and what happens remember when we start part to um sweat more that sweat is coming from our plasma volume so when we see a reduction in blood volume and or blood pressure we're going to release from the adrenal cortex something known as aldosterone when you release aldosterone what that does is it increases our sodium retention in the kidneys and a major thing about sodium in the body is wherever sodium goes water's going to follow it I don't know if you've ever had a high sodium meal uh we love crawfish boils in the South so maybe you've done a crawfish boil or you've eaten something seafood or whatever it is that has a high sodium content and the next day you notice that uh the peripheral segments of the body are swollen a little bit I've noticed it I love crawfish and all that stuff so when I eat it I can gorge myself in it but the next day I'm going to see that my fingers are in my wrist my ankles are going to be swollen a little bit the reason for that is because a high sodium content in my body causes me to retain more water so when I retain more water it causes swelling so always remember that wherever sodium goes in the body water's going to follow and that's why we want to retain sodium in the kidneys because that's going to help us to retain water in the kidneys and keep our blood volume up the other thing that we releas is ADH so ADH is an antidiuretic hormone which is also known as vasopressin so these two go hand in hand synonymously with each other comes from the posterior pituitary and it happens when you get a concentration of your plasma or of your blood so remember if I start to sweat that sweat's coming from my plasma which is going to cause a increase in the viscosity or the thickness of my blood so in other words my for formed elements within my blood are becoming more concentrated because there's not as much plasma or water to dilute it so when you get that concentration of your blood you increase the water reabsorption at the kidneys because of anti diuretic hormone diuretic means that think of things like coffee coffee works like a diuretic in the body which causes us to excrete body water content so an antidiuretic hormone is going to cause us to hold on to body water so this is what's known as the renin Angiotensin pathway so this is something that I want you to know make sure you go through this and note the steps of the renin Angiotensin aldosterone cycle so here we'll walk through each stage of it when you start to get dehydrated you're losing that plasma volume it decreases your total blood volume which leads to a decrease in pressure because we have less fluid going through the body that's going to be sensed or picked up by your jux glomular cells in the kidneys and at the same time as that low pressure blood is circulating through your liver uh your kidneys are going to release renin and your liver is going to release angiotensinogen as the blood continues to circulate through the body these two right here are going to meet renin and angiotensinogen are going to meet and they're going to create something called Angiotensin one so enzien one is in your veins so let's write that here it's in your veins and it's coming back to the right side of the heart let's just draw a heart right here so it's coming back to the right side of the heart remember the right side of the heart is going to pump blood over to the lungs inside your lungs you have something known as Ace which stands for Angiotensin converting enzyme the only role of Ace here is once the blood leaves the right side of the heart and it gets to your lungs it's got Angiotensin one in it Ace is going to convert it to Angiotensin 2 Angiotensin 2 is the active form of what we need to get all of this to correct itself so Angiotensin 2 is going to have a couple of effects here one it's going to immediately start to cause basoc constriction in your arterials and what it also does is as it reaches adrenal cortex what we said earlier you're going to release aldosterone aldosterone causes you to reabsorb sodium at the level of the kidneys wherever sodium goes water's going to follow so we reabsorb water here and that's going to bring your blood volume back up so now you have basoc constriction of your arterials and you have an increase in blood volume now what stimulated all this to happen remember we had a decrease in volume and a decrease in pressure so Vaso constriction think about this if I have fluid in the tunnel and I constrict the tunnel down and make it smaller what's going to happen to the pressure inside the tunnel hopefully you imagine that the pressure inside the tunnel is going to go up so the Vaso constriction brings my pressure back up and the increase in blood volume helps to bring that pressure back up but it also corrects this original decrease in blood volume so now I've got an increase in pressure an increase in volume so let's write that an increase in pressure and an increase in volume which in turn corrects the orig original stimulus that was causing all this renin Angiotensin aldosterone Pathway to be activated so now I've brought everything back to normal it's going to shut itself off so this is another example of a negative feedback loop in the body that helps me with Thermo regulation so definitely a very beneficial thing that happens to be able to help us regulate um our blood pressure and our our blood volume inside the body especially in a hot humid environment and this is also one of the reasons why we see an increase in plasma volume with acclamation to that environment so all of this kind of ties back into itself with our Thermo regulatory response so that gets us all the way through the thermo regulatory PowerPoint that goes in our special topics unit so make sure you go through all of this information and if you have have any questions feel free to reach out to me or post your questions on canvas under that discussions tab