Swimming and 10k: two words most people don’t expect to find in the same sentence. For new runners, the 10k distance is often the first milestone on the road to long-distance runs such as the half or full marathon. For swimmers, the 10k usually doesn’t enter conversation. There is a famous 10k swim in San Francisco that starts at the Golden Gate Bridge and ends at the Bay Bridge, but famous is relative: even that swim attracts fewer than 50 participants every year.

Spending time on the sidelines has left me searching for new challenges that I could pursue while my running goals are temporarily on hold. I’ve been toying with the idea of a double century bike ride this summer – 200 miles, and I’ve spoken to a couple friends about doing a relay swim across Lake Tahoe sans-wetsuits. I was reading Triathlete magazine last week and came across something known as the “birthday” swim set – a 100x100m workout in the pool. When I read about it, I decided that I would go for it first chance I had, and went to the pool on Saturday with only one goal in mind.

This was uncharted territory for me – although I regularly swim between 3-5 miles per week, my longest swim before Saturday was 5k (3.1 miles). Instead of treating it as a 10k swim, I decided to break it into 10×100 chunks, and brought more than enough fuel and water to top off my reserves after every set of 10.

Knowing that I would likely find myself in a very unfamiliar place after 6000m, I went easy for the first 5000m and made it a point to drink and eat as much as possible; I preferred a full stomach over a bonk. The laps ticked away, and the fuel actually propelled me much more than I expected for the first 6500m. By the time I hit 6500m, I felt fatigue that I’ve never felt before – my forearms, deltoids, and triceps were burning between the swim, my use of crutches, and the resistance work I’ve been doing recently.

By the time I hit 7000m, it felt very similar to turning the corner for the last few miles of the marathon – I only had my “normal” swim workout to go. The hardest stretch was undoubtedly 6400m-8000m – miles 4-5, where I simply had no reference point. I toughed out the last 2000m and watched my Garmin tick from 9975m to 10.00km – a sight I probably won’t witness again anytime soon. I hit the 10k mark at just over 2:30 elapsed.

Although the idea of swimming 10k in a pool may sound crazy, I would take it over sitting for 6 weeks any day. It was a good way to gauge my endurance after spending 6 weeks on the sidelines, and logging a tough workout without using my legs felt very gratifying. I can’t say that I’ll be swimming another 10k anytime soon, but if I need to get creative while I’m on the sidelines, at least I have options.