Ironman 70.3 World Champs to a 2:45 at the 125th Boston Marathon (fall edition)

David Pinsonneault
8 min readOct 19, 2021

Triathlete takes on marathon or marathoner takes on triathlon?

When I signed up for the 125th Boston Marathon, I had no idea that I would have just come off of the Ironman 70.3 World Championships 3 weeks earlier. I had no idea that I would have gotten into a bike crash 4 weeks before that. I had no idea I would only do 1 run over 20 miles in the months leading up to the race. I also did not know I would feel stronger than ever.

I have considered myself a runner for more than a decade. I absolutely love it. I love being able to see the results of what I put into training. I started off in the sport the same way many of us do — I wanted to lose some weight & make some friends. I did cross country my junior and senior years of high school. My times were nothing special. I probably should have fallen into the camp of never running another step after that but for some reason wanted to tackle long distances in college. I ran a half marathon. Then I ran another one. Then I tried a marathon. Eventually, I was able to qualify for Boston. I got my half marathon down to 1:15 and my marathon best down to 2:42. I have tried 100 mile weeks with big marathon workouts. I feel like I still have a lot more to give at those distances but running got frustrating at the end of 2019.

That’s when I got a stress reaction in my left foot. I ran my 2:42 personal best at the Berlin Marathon two weeks after that diagnosis. I didn’t run a step from then until the few days before the race. I missed training and was fighting through a lot of pain. Without some fueling mistakes, I could have run under 2:40 even with the missed training. I was on 2:39 pace through 35km. I recovered from the injury but, when I came back to running, my left achilles was still painful. I didn’t realize the achilles was as bad as the foot. It did not heal in the ~8 weeks I took off after Berlin. I was able to run through the achilles pain and ran a 1:15 half marathon in January 2020. We all know what happened next. The world stopped. Races couldn’t happen but weren’t important anymore. I kept training and kept training hard. I ran myself into the ground. My workouts got worse and worse. My pain increased to a point where I could barely walk. I had to stop running. It wasn’t working for the first time in my life. I needed something to fill the void so I bought a bike.

In the summer of 2020, I bought a 2012 used Cervelo P2. I started riding it every day. I used flat pedals and did not know clip pedals were a thing. I rode hard and started to ride longer and longer. That’s where the idea of doing triathlons started. I joined a pool and started swimming. I didn’t know how to breathe properly but I was having fun and the body was feeling good. I signed up for an Olympic Triathlon and won my age group after less than 2 months of swimming/biking training. I only did some light running in the last 3 weeks before the race and still had the 2nd fastest run split.

While I had fun at that race, I wasn’t a triathlete. I was still a runner. I wanted to try a 70.3 so I signed up for one in the summer of 2021. I would train similarly to the Olympic one and ramp up the swimming/biking as I got closer. I was still a runner and had some running goals left to accomplish. I signed up for a spring marathon but got injured in the couple of weeks before the race. The achilles was, yet again, the culprit. I ran the race and it went horribly. I was devastated. I didn’t feel like a runner. So I went all in on triathlon. I hammered out big training weeks. The nice thing was that the achilles pain was manageable because I had to balance all 3 disciplines. 70–80+ miles/week was too much for the achilles but 40 miles a week, with a ton of swimming/biking, felt great. I nailed my debut. I finished 15th at Musselman 70.3 in 4:25. I turned in a 1:19-flat half marathon run split, which was the 2nd fastest out of the entire field. I had never felt stronger running.

I quickly shifted focus to the 70.3 World Champs. I had qualified and I simply had to go. Boston became an afterthought. I signed up for Timberman in between to give myself another shot at the 70.3 distance. In the back of my mind, I wanted to see how close I could get to an elite qualifying time for triathlon. After a strong swim (for me), I had bike trouble and ended up crashing. The pain was awful. It hurt to breathe. I had X-rays done and, luckily, my ribs were just bruised. I couldn’t swim or run. The pain was too much so I hammered the bike but missed some valuable training time before Worlds. After that experience, I went into Worlds a lot less confident. My racing showed. I had a sub-par swim. My bike started strong but then it started to rain and hail. The wind picked up and we saw 50mph gusts. I was terrified, after falling just 4 weeks prior. I was still having rib pain. I slowed down to a crawl on the bike. My anxiety was heightened. I wanted nothing more than to get off the bike. I had an average run and finished a lot higher up than I had thought I could. Some people didn’t back off during the bad weather. I was on the extreme end of the spectrum and did what I thought I needed to do. After that adventure, I still had the Boston Marathon on the calendar in 3 weeks…

After not running more than 40–50 miles/week in months, I crammed hard for the race. I ran as many miles as I could fit in. I ran a 22 mile long run 16 days out. I did an 8 mile tempo in the 5:50s. I was as ready as I was going to be. We were greeted on race day with temperatures in the 60s, a dew point close to 60, and a slight headwind. It wasn’t horrible but those also aren’t PR conditions. I just want one marathon where I stay healthy, get in the training, and catch a 40 degree day on race day. Boston 2021 had other plans. Triathlon has taught me how to pace and how to fuel. I wanted to run 6:00/mile but adjusted to 6:15 based on the forecast. I took an extra gel with me and planned to drink more than I normally would.


When the gun went off, a lot of people naturally hit it hard. Good marathons don’t happen with fast opening miles. Good marathons happen with even pacing or negative splits. I started off at 6:20 pace and ran that pace through 10k. After that, I started running 6:10–6:15. I maintained that pace through 16 miles, when the hills started. Although I didn’t have the traditional long runs in my legs and tempo runs, my body felt strong. I did have a lot of long rides in my legs and threshold work. I felt in control. I attacked the hills. I ran slightly stronger there than in 2018. I split a 6-flat mile 22 and held it together the best I could. I went from running 6:10s to 6:20s for mile 24 & 25, before getting it back in the last mile.

Given my lack of specific marathon training, I would say the marathon went as good as it could have. I positive split by less than 1:00. The Boston course is a bit tougher in the back half imo. I ran 2:45 on a day that wasn’t meant for peak marathon running. I ran 2:45 in a marathon that I hadn’t really been training for. That is a testament to all of the training I have put in over the last year. I felt strong throughout the race and know that I had a PR in me on a better weather day. I think my history of running marathons & having several big marathon training blocks helped me run well on Marathon Monday. I also think triathlon training made me strong and taught me a lot about managing fatigue. You know what your body needs when you have some some really long training days in the bank.

Right on Hereford, Left on Boylston

I do not think triathlon training has gotten me faster for anything under 10k. I am naturally losing any speed I might have had as I get older. Triathlon training is definitely getting me really strong from threshold to marathon pace. Now, all I want to do is run a marathon on a cool day. I, however, do not know when that will happen. The shift has already begun. I am passing on Boston in 2022 to focus on triathlon. I flirted with the idea of a late season or winter marathon but that is counter-productive to improving at triathlon. It is hard to keep up with swimming/biking when you are trying to run your best. Not being able to do it all is something I am grappling with. Triathlon has had its challenges but it is still new and exciting. I dropped a quality 70.3 debut with less than a year of swimming/biking under my belt. I do not think it is outrageous to go after my elite triathlon card. I have already qualified as an elite duathlete (running/biking) but that doesn’t open as many doors. There aren’t a ton of pro races available and there aren’t great sponsorship dollars available. I don’t think I would ever get to the point of being able to quit my day job but racing as an elite for Ironman races is a dream that doesn’t seem so far away. I’m a lot closer than I ever was when my only focus was running. I need to swim and bike as much as I can. I run as well as a mid-level professional. If I can close the gap in the other two areas, I think I have what it takes to join the elite ranks.

As I write this, it is becoming more clear. I need to go all in on triathlon and give this a real shot. If I miss, I’ll be content in knowing that I tried. It stings that my running PBs are soft in my eyes when I committed so much time and energy to the sport. I feel like I overtrained a lot and never raced as well as I could based on past training. This new chapter is about flipping that script. I’m going to train as hard as ever. Triathlon requires more hours than running. I’m also going to race as hard as ever. I’ll still hit some big workouts along the way but I want my racing to do the talking. I believe I can get to the elite side of the sport. That’s pretty cool for someone who couldn’t fathom breaking 20:00 for 5k a decade ago, and has been at this triathlon thing for a year. Stay tuned. There’s a lot in store in 2022 (& maybe even at the end of 2021).



David Pinsonneault

Union/Political Organizer @SEIU. Alum @BarackObama. Chicago living. Blood clot survivor. 15x marathon finisher. Always looking for better.