I was hungover on my 40th birthday. Decided to go for a fast 5k and ran a 19:32. I don't normally run 100% for a 5k, so I'm not sure about the timing. I tend to do a fast 5k session once a month and aim for 85%. I wanted a sub 20 5k on my 40th, however, as a sort of goal that I thought I could clear without any extra training. I do wish I hadn't have drank the night before but I'm still happy with that result.

edit/ I had a bourbon and then 6 IPAs that night. Which is a pretty big / unusual session for me. I'm 6'0" and at the time I weighed around 170 lbs.

I also just recalled another "fast" run that I had on a hangover and wanted to share. I ran my half marathon PR hungover on maybe 3 hours of sleep. Stayed with a friend in Haight-Ashbury, who I hadn't seen in probably 5 years at the time, stayed up drinking til 3am, and then ran the first half of the SF marathon. I ran a 1:41 that day and I'm still not entirely sure how it happened. My normal half times are around 1:45-1:50.

I’m not sure times are really the point, and certainly not the most recent handful. I’ve never been objectively fast - I’m a big bloke, and have asthma severe enough that I’m on 4 drugs for it daily and was told to shield by my GP/consultant. Plus, I’ve run hundreds of 5kms so cherry picking the last few post-booze outings would say nothing evidential about my original statement, which is that many of my best times ever have been after a big night.

I will offer that my PB was at 9am (Parkrun) after a night on which I drank at least 5 beers, likely more (it was a celebration).