Marcin Lewandowski.
Spike's has a great feature on him and his brother, Tomasz, who is his coach.
“He runs 170-180km a week during the winter months,†says Tomasz. “He gets one day off each week, usually Sunday. He never strictly prepares for the indoor season. We treat it as a break to see the effects of training. His training is a mixture of all motor aspects: he is able to clock 10.5 for 100m, 47.0 for 400m and also get under 30 minutes for 10km, all in training."
https://spikes.iaaf.org/post/lewandowski-a-tale-of-two-brothers
The story has a great anecdote about how he wasn't planning on running indoors this year but then he heard about a 1-year old girl who needed a ton of money for life-saving heart surgery. He ran a race for her and donated all of his of money to her. He broke 3:40 so he kept going and ended up winning European indoor gold. He gave her all his dough.