​James' HR training diary weeks 8 & 9: The half marathon

We run our first half marathon – but can HR help us set a personal best?
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Apologies for the week's hiatus, but I was on holiday in Scotland – and preparing for Sunday's Reigate Half Marathon. 13.1 miles to prove whether the last two months of training have achieved anything worthwhile. How close could I get to that coveted 1:45?

For first-time readers, I've transformed my training and thrown it at the mercy of wearable tech. In a bid to understand how the green flashing optical heart rate monitors can transform training and how listening to your heart can change the way you run, I'm now training via bpm. I want to find out whether the benefits of heart rate training are open to every ability, not just star athletes.

Now, eagle-eyed diary readers might realise that the timings are off. I'm following a 12 week plan provided by Greg Whyte, Fitbit's ambassador and former Olympian, but in the time it took to get the plan underway, Reigate actually fell in week nine. The good news is that thanks to TomTom, I have a place at Royal Parks Half Marathon on 9 October, which is the natural end of the plan. So this week's Reigate race is a great early indicator of whether I could shave 15 mins off my half marathon PB.

In week eight I managed to get a full week of four training runs in, including successful interval sessions. I deviated a little from Greg's plan in order to test the Fitbit Charge 2's heart rate performance, which you can read about in detail in our review.

I managed to get out for a 45 minute fartlek session with 5 x 1 min hard/slow built in, followed by 30 mins of LT running with 5 x 30 second hill sprints. The final run of the week was a 60 minute run with 20 mins of AT2 built-in, which I achieved by running up a huge Scottish hill, and could have been the final key to my race achievements.

Having spent the last two months training via heart rate I've learned something very important: my performances drop when I'm tired from training – that's quantifiable. So I made the decision to not run at all in the week leading up to the race.

It was a bit of a gamble, as even Greg's training accounted for tapered runs in the week before the big race. But my feeling was that my pace was always better when fresh – and a few days off wouldn't hurt.

I ran Reigate back in 2014 and I know it's not easy – plenty of little hills gives the illusion you're constantly climbing. So I stood on the start line of Reigate Half Marathon with a plan. Based on my previous run's pace I would start at 8:40 min/mile for the first mile while my heart rate got up to an even level, I would then switch over to holding my heart at about 170-173bpm, which I'd been using in training, and forget about pace as much as I could. That was the bpm that yielded my 10K PB in week six, so a good rate to test in this race. You might say it's conservative, but this is my first race since my busted hip at the Amsterdam marathon in 2014.

Out running #reigatehalfmarathon. TomTom Spark armed and ready to run. #170bpm
A photo posted by Wareable (@wareable) on

So I started the race, and was expecting the inevitable big climb followed by downhill. I knew it would be difficult to manage heart rate here so I tried to stick to my pace. The beginning of a race is always tough to manage with adrenaline, let alone big hills to negotiate, and I felt I delivered this part well – and in mile two it was time to switch to heart rate.

Was I in for a surprise? I was ticking at nearly 180bpm a mile in. That's so high for me in terms of a race pace. I tried to ease off and I did manage to bring it down to 165 and control it back to 170 (always a good sign when you can manipulate your heart rate in a run like that) but I couldn't hold it.

​James' HR training diary weeks 8 & 9: The half marathon

This worried me for the first four miles – I've never run near 180bpm for more than a couple of miles. How could I hold that for 13?

After a few miles I realised that the race was a different story. The adrenaline was causing my body to act differently. I was running within myself at 8:20/mile, faster than in training. I could hold the higher heart rate. But I was still concerned about burning out, so I opted to run the race by heart rate, scrapping the old plan and ensuring I stayed at under 180bpm.

This worked well, as the second half of the course became extremely hilly. Controlling my heart to remain under 180bpm ensured that each hill didn't tip me over the edge. I'm a psychological runner, I don't like negative thoughts entering my mind. Questioning whether I can complete a run is enough to ensure I don't.

And I'm glad I left something in the tank. Just as I finished calculating that two blistering miles at the end would give me a 1:49, I was hit by something unexpected: the Reigate route had changed, to leave an enormous hill at mile 12. Running it was hard enough, let alone swerving people who were stopping half way up. But I made it up and pushed down the big hill after. At 12.5 miles heart rate was out of the window, it was all about getting to the finish. I wasn't sure if I could make it when the watch said 0.3 miles to go, but in no time the finish line was in sight, and I could sprint down the straight for a 1:51:15.

It's 10 minutes off my previous PB on a tough course. Constantly undulating, with the whole race seemingly a gentle uphill climb with a killer finish at mile 12 – I'm happy with my 1:51. And my aim to go for 1:45 by the end of Greg's training regime? Well, this is encouraging. There are three weeks of training to go, and my strong finish means I can take confidence into the flatter Royal Parks. Six minutes is a lot in three weeks – but a good Reigate time means I'm up for going fast next time out.

Image credit: Sussex Sport Photography

Check out the rest of the diary

Week 1: Getting assessed

Week 2: Feeling the heat

Week 3: HR making sense

Week 4: Interval fail

Week 5: The revenge of the interval

Week 6: Pain and again

Week 7: Putting my HR to the test

TAGGED Sport Running

How we test

James Stables


James is the co-founder of Wareable, and he has been a technology journalist for 15 years.

He started his career at Future Publishing, James became the features editor of T3 Magazine and T3.com and was a regular contributor to TechRadar – before leaving Future Publishing to found Wareable in 2014.

James has been at the helm of Wareable since 2014 and has become one of the leading experts in wearable technologies globally. He has reviewed, tested, and covered pretty much every wearable on the market, and is passionate about the evolving industry, and wearables helping people achieve healthier and happier lives.

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