Contrast Therapy
Hot, cold, and the honest state of the evidence for alternating between them.
Contrast therapy is the reason this site has two colours. Cedar is heat, ice is cold, and the interesting claim is that alternating between them does something neither does alone.
That claim is also where the evidence gets thin, and we are not going to pretend otherwise. What we can do honestly is the part nobody else bothers with: tell you which half to buy first, what running both costs, and what the published research does and does not support. If you only have budget for one, start here.