Yes, I believe he is. Will be interesting to see the results. My own anecdotal observations of cold water effect: I have significant issues with OI and blood pooling in the feet and this is unsurprisingly particularly bad when taking a hot shower. A shower seat stops me from fainting altogether but that's about all. My shower takes a little while to heat up and the cold water coming out initially is very, very cold. I've taken to directing that painfully cold water on to my lower legs (knees down) and feet. The idea was that it would constrict the blood vessels and thus reduce the blood pooling once the shower heats up. I don't know if my hypothesis of the mechanism is correct - maybe it has something to do with sympathetic/parasympathetic/vagal tone/HRV instead? - but it is quite effective. I get through my shower much better. I only measure HRV once a day, about 4 hours after I have my shower. There is no difference between days when I do have a shower and days when I don't (only comparing 'good' days with or without showers, and excluding PEM days when I never have showers and when my HRV is down because of PEM). So if there is any HRV effect at all it looks to be a very short term one.