Why are 5k races so awful?
To non-runners, the marathon is often seen as the pinnacle of our sport. It’s the big, impressive distance that earns all the kudos. And yes, running a marathon is a big deal. But I’d argue that running hard over any distance is a huge challenge.
Pushing yourself to run as fast as you can over a set distance hurts. The longer the race, the longer you sit in that pain. But the shorter the race, the more intense that discomfort becomes. A 5K might be over relatively quickly compared to a half marathon or marathon, but for those 20-or-so minutes, it can be just as gruelling.
Why 5K races are so hard
Physiologically, a 5K pushes your body close to its limits. You’re working just below or at your lactate threshold - the point where your muscles start producing lactic acid faster than your body can clear it. Hence the burn. Your heart rate climbs quickly and stays high, oxygen demand is intense, and your body relies heavily on carbohydrate stores for fuel.
Unlike longer races that require pacing and energy conservation, a 5K races demand that you go out fast, get your heart rate soaring, and sit with that discomfort all the way to the finish line.
This summer, I’ve set myself the goal of running a sub-20-minute 5K. That means not only pushing myself hard, but also pacing it right — not blowing up too early and paying for it later.
Race 1: Show up and blow up
The first race in this block was at parkrun in May and I used it as a benchmark to see where I was starting from. I was confident going into it - perhaps too confident. I set off way too fast, clocked a super-quick (for me) first mile, and by halfway I was dry-heaving into a bush.
If my partner and son hadn’t been waiting for me in the playground mid-course, I think I would’ve ducked out and gone home, quietly licking my wounds. But with them watching, I had to keep going. I found a way to get to the finish line, even though I desperately wanted to lie down and disappear.
Time: 22:06
Lesson: Don’t go out TOO fast
Race 2: The Course Matters
The second attempt was a local Wednesday night 5K, part of our running club’s championship. It’s a tricky course: you have to get a strong start to secure your place before a narrow gate onto a flyover, and a road crossing adds extra chaos.
It was humid, but not unbearable. I didn’t go out too fast this time (lesson learnt) and got through the technical sections without issue. But heading into the final stretch, I felt like I had more in the tank, yet couldn’t get my legs to turn over any quicker. The speed just wasn’t there.
I wasn’t expecting a sub-20 yet, but I couldn’t help feeling a bit disappointed at how far off I still was.
Time: 21:12
Lesson: Choose your course
Race 3: School Trips and Club Nights
This one came this week at the end of a busy day. I’d been on a school trip with my son’s class - a full day of herding small children and being on my feet a lot.
That evening, my club was hosting a 5K race. I was down to volunteer, but my role was handing out race numbers. This meant I could do my job and then jump into the race.
It was humid again and the air felt heavy. Other clubmates were marshalling which meant I got cheers all along the course. This gave me the extra boost to keep pushing when I wanted to back off. I tried not to look at my watch other than when the mile splits popped up. I knew going into mile 3 that I could get under 21 minutes if I just kept my foot on the gas.
I finished just 11 seconds over my PB but feeling absolutely wrecked. I thought someone was going to have to hold me up at the finish.
Time: 20:39
Lesson: Lean into the discomfort
Where to next?
Taking a minute and a half off my 5k time over the course of a few weeks wasn’t down to training, it was through all the other bits: pacing, getting comfortable being uncomfortable and having the right (or at least better) racing conditions.
Now it’s a matter of focussing on the training: getting the intervals in and putting myself in the right race at the right time. There’s still a couple of months of summer left.
Have you raced a 5K recently, or are you training for one? I’d love to hear how it went. Hit reply or drop a comment and let me know what your toughest or most satisfying 5K felt like.