跑去搞醫療問題的大牛 Xavier Amatriain 說：
I have run maybe around 30 marathons, 6 of them this year (2016). I have only done a PhD and most likely won’t be doing another one in my life. So, in that sense, a PhD is “harder” than a marathon. However, the word “harder” is a bit vague, so it really depends on what “hard” means to you.
接著一位 UCDavis 的物理系助理教授，自稱跑了二十幾次馬拉松，在 2014 年的里程數是 3700 英里，她直接了當的說，幸好我這輩子只唸了一次博士，何者難度較高不言可喻。
I have done both, fortunately just once for the PhD.
總之，整個頁面的基調就是 I’ve done both and the PhD is far more difficult to complete。