DR. GISOLFI: Not to my knowledge, just having an increased subcutaneous layer of fat does not influence the sweating response.
PARTICIPANT: I have another question about age. Do you have any data on general range?
DR. GISOLFI: There doesn't seem to be a difference in the sweating response up to about 50 or 55. When you get over 60 and it is more clear over 70 years of age, then there is a decrement in the sweating response.
The individuals that Robinson studied (Robinson et al., 1986) were over 60. I think the mean age was something like 61 or 62 years. There was a decrement in the sweating response, but it wasn't reflected in their ability to regulate their body temperature which is, again, the more important point.
PARTICIPANT: Carl, in 1980 Dimri published a review of 55 papers in which he looked at this last point that you mentioned here, the increase in sweating rate during a 7-to 10-day period of heat acclimation (Dimri et al., 1980).
He found in those 55 papers that 15 of them showed no increase in the sweating rate. I know you published a paper at least once that showed no increase in the sweating rate during the deacclimation of 7 to 10 days. Could you comment on that for us?
DR. GISOLFI: I think it depends on the level of fitness of the subject. If you are dealing with a relatively fit individual that you then heat acclimatize, you probably see little change in the sweating response.
If you are dealing with people who are terribly unfit and you heat acclimatize them, you will see a rather substantial elevation in the sweating response.
PARTICIPANT: And also I know you mentioned that in dry environments when you published these studies, for hot, dry and wet, dry environments, there was less of an increase in the sweating range.
PARTICIPANT: At the initiation of exercise, there is an immediate drop or increase in plasma osmolality that doesn't seem to be such in the sweating. That is, there seems to be a movement of fluid from the blood volume to intracellular volume.
I am wondering whether that is due to being acclimatized and unacclimatized and to what extent does that shift in plasma volume affect the sweat rate.
DR. GISOLFI: Initially, I don't think plasma volume and plasma tonicity have a marked influence on sweat rate. The sweating response is being driven primarily by an increase in core body temperature and secondarily by changes in skin temperature.