Thought I had Zone 2 under control. Lessons from longer runs.

2026 Day 172. #RunnyDays.

To get my mileage up, I have been consistently running at a zone 2 pace for the majority of my workouts. Every once in a while I do an interval session to keep in touch with relative speed. With practice, I was running at 130bpm — 7' min/km which is good but nothing amazing.

I thought I could keep running forever at that pace and my heartbeat would only see a slight increase. My recent 15K (which I ran on a whim by the way and does not even phase me anymore) revealed a lot missing in my preparation.

My training involved mostly 5Ks and some functional strength training. This seemed to be working great when I stayed confined within this. Over a longer run, I realised that keeping up the pace was not hard, but keeping my heart rate low was an issue.

An aside. I run early in the morning when the wind is cooler and there is less sun around. As the run was longer, I was running in a hotter environment than I was used to. The heat could have also contributed to the rise in my heart rate but not by that much.

As I was hitting the 10K mark, I started noticing that I was running at 140–150bpm at the same pace. I thought it was because I had not been breathing in a a rhythm, but that was far from the actual problem.

I was sweating, I could feel it all over, I could feel it as it burned my eyes if I did not wipe it off. I was not tired but I was extremely warm. I felt like my core radiating heat and wanted to be let off. Is this was Thomas felt like everyday?

By the final kilometres my clothes were now drenched in sweat, I ran faster just to get it over with. The distance was not too bad, but the overall feeling of running in such an uncomfortable attire was getting to me.

My heart rate ranged from 109bpm (first kilometre) to 160bpm (last kilometre). The average, according to my watch, was 137 which is not bad considering the object of the run.

I felt horrible after it, worse than I did at my previous attempts. The metrics are also kind of embarrassing to share.

Previous PR attempt — 6'30" min/km pace — 150 bpm

Zone 2 attempt — 7'13" min/km pace — 137 bpm

The biggest difference in the two runs was the temperature.

My PR was in February when the temperature ranged 9–22 centigrade.

Currently the temperature ranges 22–40 centigrade.

Obviously this is a major difference. It is like I am running in two different places even though it is the same route.

I can only pray that the summer heat is messing up with my metrics. The only way to try this out is to continue training until February comes around again and then go for another attempt.

It would have to major shift for me to be happy. A year’s worth of training effort should help me keep my bpm lower even if I decide to run at the same pace.

One of my goals for this year was to run a marathon by July, but seeing how badly the heat is affecting me, it does not seem like a great idea. I am not worried about setting a great time but I am worried about how absolutely horrible would it be and how much I would need to cool down. I do not thing the summer is the best time to do this.

It’s not great to give up on your new year’s plans but better late than never.

See you tomorrow.