Finally, a sub-4 marathon

Jan 6, 2025 · 2 min read

I have been dreaming of a sub-4 hour marathon for quite some time.

Sub-4 may not sound hard for many marathon runners as many aim for sub-3.

But it is a good enough goal for me.

Marathons are very interesting endeavors. Many people have run a 5K or maybe a 10K. One might think that a marathon is just eight and a half 5Ks or four 10Ks stacked up together, one after another.

No, no, no. That couldn’t be further from the truth.

A marathon requires you to pace yourself within your limit for the first 20 miles (but still as fast as possible), then push yourself and grind for the last 6 miles. This is how I feel this time.

I cramped around the 21-mile mark, around three hours into the race, which was hot, humid, and exposed to unshaded direct sunlight. I was on target for a sub-4 marathon, which would be 30 minutes faster than my previous best record. At that moment, I could have decided to give up and start to walk, as many others on the course did. That’s probably what I would have done in the past. After all, if there seems to be no hope of achieving my goal, why bother?

But wait, why do I doubt myself? Have I already given all I have? If not, how can I be sure I will not achieve my sub-4 goal?

I just kept going. I was slower than before but tried to keep a steady pace. The last 50 minutes were more torturing than the first 3 hours combined.

I did it! 3 hours and 56 minutes!

Lesson learned: Never give up until you have given your all!

Shibo Chen
Authors
Senior Architecture Engineer
Shibo Chen is a senior architecture engineer at Tenstorrent building next-generation high-performance RISC-V CPU. He received his PhD from the University of Michigan in 2025.