Combine these three lines together and look at any level of heat production, the rate of sweat. As heat production goes up, sweat rate increases proportionally. For any given rate of heat production, if you are at a hotter more humid environment, you produce even more sweat. As the number gets to 28- that’s really hot and really humid- a lot of radiant heat. Sweat rate is much higher at this work rate than it is at 10. Ride a bike at 20 mph, you will produce an amount of sweat. Ride that same bike ride in the middle summer, producing way more sweat at the same work rate. As body temperature goes up, sweat rate goes up- it’s trying to compensate. o Going up 1 degree, won’t change that much o As you increase more than that, sweat rate will increase even more. As you increase exercise duration, increase sweat rate, especially in a hot environment. o What the problem with the graph on the right?? The rectile temperature is the measure of core body temperature. Describe that environment. It says hot. Does anyone want to exercise in that environment? No. their sweat rate increases more and more. Can they compensate for it? Can they balance this equation to get heat storage to zero? No they cant because if they could rectile temp would plateau but it continues to go up and up and up. This is called non- compensational heat stress. Your body cannot compensate for this heat stress. o This can be driven by environment, how hard you are working, or equipment. o Football players can’t lose sweat because of the equipment. Heat dissipation during exercise Sweat can dissipate heat proportional to the air temperature
o Convective and Radiative heat loss decrease in hot environments o What happens in a humid environment? Evaporative heat loss is gone, and heat gain and body temperature becomes non-compensable heat stress. Sweat will just roll off to the floor and will not be effective at cooling. o o Ambient means ____. o What’s the air temperature in this room? 20-22 C. about the middle oft his chart. o This gap is the work rate o Going from cold to hot environments, convective and radiative heat loss goes down. In a cold environment you don’t sweat a whole lot because you lose heat through Covnection and radiation. Hot environment, evaporation takes place. o Look what happens to convection and radiation heat loss when room temperature is higher than body temperature—it turns into a HEAT GAIN, which is why evaporation must take place. What is the effect of increasing sweat rate? Plasma volume decreases Plasma electrolyte concentrations increase Sweat is more dilute than plasma
Look at plasma vs sweat Plasma sodium levels are 140, sweat are 40. Lose more liquid than salts when you sweat. This makes you actually concentrate the blood. After exercise, plasma potassium, chloride, and sodium levels are higher because you are losing more water than you are salt!!!!
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- Fall '09
- kinesiology, heart rate, VO2, METS