I find that hard to believe. I spent a winter in Helsinki, which is roughly 2 to 4 K warmer than Moscow, and you barely spend any time outside below -15°C (5°F)

I find that hard to believe. I spent a winter in Helsinki, which is roughly 2 to 4 K warmer than Moscow, and you barely spend any time outside below -15°C (5°F), why would you do that? It's probably dark anyway. What probably did happen is that he spent a lot more time indoors and not doing sports if he's not an avid gym rat.