I’ve got a ‘sort of’ answer for you folks......
I’m into week 9 of the Wim Hof Fundamentals course....
I came across Wim Hof about 3 years ago, and wrote it off as too extreme
(the cold showers I didn’t fancy at all)
I started cold showers end of August, but hardly a minute.
Week 9 is 5 minutes cold straight off. Earlier weeks you have the bliss of warm for as long as you like, then a minute cold, slowly building up to 2 minutes cold, warm unlimited, 3 minutes cold...
The 5 minutes cold is definitely brutal, makes the head (and other parts ache)....but you feel very alive and invigorated after it.
Before the cold showers there is a sequence of deep breathing.
It definitely resets your system...
I’ve not been riding much due to the cold spell, too icy and all that, but walking and a bit of wetsuit outdoor swimming.
Sunday I took a dip outdoors without wetsuit... a doddle compared to the shower, but I only stayed in for a minute, and didn’t swim, just a ‘dip’ without head under.
I was experimenting. Next time it’ll be a swim.... (with a tow float)
If you do crawl your (well, mine) head is under most of the time.
All geared up for January BAM with the fatbike tonight... but... MOJO ?
Peeing down outside, and forecast is 10degrees
Called it off. Too warm !
I’ll wait till it gets a bit colder....
I’m determined that January BAM will be a pleasant and toasty experience, so bike is packed with my old Rab sleeping bag, it weighs 4 lbs, (AND a full length Thermarest ) and I bought it for my crazy coast to coast Oban to Aberdeen in 1997, end of October... alone

risky.... but it was a good experience
First night ice inside tent, and water bottle froze, but in that bag I was warm
So to get the mojo going try a warm shower followed by a minute cold....
And good luck
PS - I bet Colin can vouch for this if he swims in Loch Morlich