Smashed my Half Marathon PB

After a recent recovery run I was surprised to find that I can now stay in HR Zone 2 on gentle hills, and average just over 5:00 min/km for a 10 km run. The pace made me feel as though I could keep it up for hours, and I started to think. My first attempt at a half back in 2016 took me 1:58:29 at 5:37 min/km. I was dehydrated to begin with, took no water with me and hadn’t trained, but I’d run my first half, even though I only set out for 10k at the time. Later that year I tried again, this time having followed a BUPA training programme for beginners. I was now down to 1:55:33 and 5:25 min/km – a whole 3 minutes faster.

Third Attempt

Both those times make enticing targets when you’ve just completed 10k at 5:00 and feel like you can run all day. Could I shave half a minute per kilometre off my PB? I decided to increase the distance each week while aiming for the same average pace, starting with 15 km and working my way up. Only I never learn, and after 15 km I just kept going because the scenery was nice and I felt great. My unplanned route featured a lot more hills than the previous attempts – 375 meters elevation gain versus 56 and 52 meters – but the views from Groudle Road and Marine Drive were more than worth it.

Pretty coastline road in the sunshine
Runner’s Dream: Marine Drive out of Douglas

If there’s a downside to running ad-hoc it’s that you might end up further from home than planned, and that was certainly true today. Grinning like the proverbial Cheshire Cat I crossed the imaginary half marathon finish line coming back into Douglas, only now I was getting quite tired with six or seven kilometres still to go, and all of it uphill. Both knees started aching properly around 25 km so I finished the day with some sprint / walk intervals and earned my second PB that day for furthest run at 28.9 km. Well, kind of. The intervals included walking, so not technically a whole run, but I’m taking it.


I’m extremely happy with this run, even if I narrowly missed my target of 5:00 min/km. Damn those hills. In the end I had enough left in the boiler to run home from the sea terminal, and that makes me wonder what I might achieve next time. Could I dial in a faster pace, or aim for a higher average HR? My Garmin Fenix tells me that recovery time is just 23 hours (3.5 days last time) and that there was 0.0 anaerobic benefit, which I’m taking as confirmation of a steady pace and reasonably flat course.

On another positive note, my vertical oscillation and ground contact times are way down, which means I’m running more efficiently and not bouncing up and down as much. Stride length is the same and cadence is up, yet the biggest improvement is probably reflected by the times I spent in various heart rate zones. It’s not a 100% accurate comparison since I’m now using HR zones based on lactate threshold and back then they were based on % maximum, but still, the graphs speak for themselves.

Big image showing statistics from Garmin Connect
Today’s Statistic Overload
Table showing statistics from my three half marathon attempts so far
My Half Marathon story so far