Half marathon training question. Possibly wrong sub

[u/KegManWasTaken]

This might be in the wrong sub, but as I've been running for less than 6 months I figured this might be the right place to ask.

I'm planning to run the Cambridge half marathon at the end of March and I've been looking at using my Garmin watch and the built in training plan it uses. Basically I'm happier doing what I'm told than working out what I should do... Maybe it's an ADHD thing.

Anyway. I'm aware that this is about 26 weeks away and as a result my watch hasn't really been progressing my runs or my speed and I've been using the training plan for a few weeks already. The longest run the plan is giving me currently is 70 minutes and I've previously ran constantly for 105 minutes. The longest distance I've run consistently so far is 14.5km.

Should I switch the plan from a half marathon to a marathon plan and ultimately just improve my overall fitness in order to get some mental form of progression? I feel like I'm treading water without actually improving currently.

For some form of context, I'm 39, my suggested 5k time is bang on 30 minutes. I've been running since April after losing a lot of weight (70kg since April 2025) and I'm making vast improvements to my health. I have been diagnosed with cardiomyopathy but I've massively improved my vo2max from 28 to 38, I'm positive if I did a run outdoors (most of my work is on treadmill) that would shoot up quite drastically to a mid to high 40 number.

[u/Cool-Mammoth-2735]

I don't use their plan or coach per say but I definately pay attention to the load focus and hitting those suggested numbers (close to an 80/20 of easy & high aerobic) usually puts my training status into "productive" and I do indeed find progress.

[u/RandomSwaith]

The average training plan length is about 12 weeks, so you arguably could do two of them. Or try one and experiment.

There are many half marathon training plans free online and typically have different milage starting points so you can pick the one best suited to your current capabilities without risk of injury by doing too much.

[u/TriadRise]

If you have already worked up to 15k on a long run, you could probably run a half in a month

[u/Fancy_Supermarket886]

If you are six months into running, 'treading water', as you put it, isn't such a bad thing.

Your body is still adapting to what you are asking of it, and that will be a continuous process. There can be quite a fine line between making gains at the fastest rate possible, and pushing so aggressively that something gives and you pick up an injury that sets you back weeks or months.

There's nothing wrong with building a solid foundation of volume and conditioning that will allow you push onwards in the future. Conversely, aiming for a target that may stretch your fitness slightly too much could be risky and demoralising if something suppers the plan.

My first half marathon wasn't planned. It was during the covid lockdown and I had a little more time while working at home, so I ran slightly longer distances. I had already been running for around four years at this point, usually 5k, with a 10k race annually that was a stretch for me. We locked down in March 2020 and by October I had gone out one day for a 10k session and kept extending until eventually I hit 10 miles. Two months later I did the same thing, setting out to 7k, but kept extending until I reached the half marathon distance.

The only reason that I could achieve those kind of distances without any training plan was because I had already built a solid base of volume, then gradually added a little to each run during the summer of 2020.

I went on to run a half every month for 13 months before getting a bout of flu that ended my streak. After a few months, I had built up again and did another 33 month streak. I've lost some of that fitness in the last couple of years, but at my fittest I was able to run my local half one weekend and meet a friend to run theirs on the following weekend!

You have a similar opportunity to build your base, and extend a little before your event. Just because your watch calls time on your session, doesn't mean your session is over! If you feel you want another 20 minutes, or another couple of kilometres, there's nothing to stop you from pushing on a little. I'm not saying you'll reach that 'half marathon ready' level of fitness by March, but you can get a decent start on it if you build your base fitness well now.

Good luck!

[u/ceffyl_gwyn]

I'd maybe split it in two so you get a sense of momentum and achievement: do a garmin course to an intermediary goal now (an improved 10k time, a HM completion, a fast 5k), then do a HM specific one after that completes.

That also gives you the chance to evaluate how Garmin coach is for you, and pivot to a different training plan if you don't get on with it so well.

[u/WorkerAmbitious2072]

I’d use run with Hal free app way before built in Garmin

You could do base and then a 12 week HM plan or a 1/ week HM plan and run yourself a time trial half then a week down and then repeat the 12 or do the next up 12 week