When endurance training works

I’ve written at length about MAF training, or more specifically, the ineffectiveness of low heart-rate training especially when linked to age. It seems to me that most people don’t understand what is meant when it’s said building endurance will help them get faster. I hope this post will be useful by giving an example of when it works and how it affects your runs.

In September 2017 I ran the Solent half marathon in 1hr36. I set off way too quickly – running the first quarter mile at about 6:20/mile pace and the first mile coming in at 6:41. After that it was a slide as my endurance failed me and I got slower by the mile. Around mile 9 the course turned up hill which made the slowdown even more pronounced until I managed a final effort to the finish line. Here’s a graph clearly showing the decline!

After a week of recovery running, I embarked on building my endurance using my own method which doesn’t involve having my watch beep at me to stay under a certain heart-rate. Following a simple schedule of one hour Steady endurance runs on Tuesday and Fridays with a long run on a Sunday, I slotted in recovery runs lasting up to an hour on the other days. This gave me a total of around eight weeks where I was hitting around 60 miles – with a peak of 69 in mid-November.

Over these eight weeks, I took only one rest day and yet my legs were always ready to run the key Steady and Long runs. Each run I marvelled at how well it went and doubted that I would be able to repeat it a few days later. Yet each run came up and I never felt too tired or got injured. I could barely believe how my legs kept churning out the miles.

I ran the half marathon on September 24th where the pace began at 6:41 and just got slower. Two months later, on November 29th, I ran along the seafront for nine miles and here’s what the splits looked like:

After a first mile at 7:14 where my body was still warming up, each subsequent mile came in at 7:01 or faster. Mile 4 was the fastest at 6:51 but I barely slowed down. The time for these nine miles was 1:02:48 (avg. pace 6:59/mile).

Compare that to the first nine miles of my half marathon which were 1:03:57 (avg. pace 7:06/mile). You might think there isn’t much of a difference but remember this was a training run, not a race. I was doing this sort of run every three days, not taking a recovery week after it.

Remember that by the ninth mile of the race I was down to 7:39; here I was still at 7:01. The gap would only have got wider – it’s very clear to see here.

I ran a hard parkrun three days later on December 2nd. My last one had been in mid-August when I clocked 20:29; this time it was 19:37 – almost a minute faster. On my Steady runs I was only hitting a fastest mile at around 6:50/mile, on parkrunday I was able to push harder and run at 6:15/mile even though I’d done no training at that level in months.

Mile 1Mile 2Mile 3Last 0.11
19 August06:1606:4306:4906:1020:29
02 December06:1306:1106:2305:3619:37
(Apologies for using mile splits on a 5k but it’s easier for reference against the other data)

At both parkruns I set off with a fast first mile of around 6:15 but, before the endurance training I slowed significantly in the second and third miles just like when I ran the half marathon. On the latter parkrun, the endurance training came to the fore and while I still set off quickly the decline by the 3rd mile was much less. I remember running that day and it feeling like I had a booster on top of the endurance runs I’d been doing – an extra 30-40secs/mile dug out for when I raced.


It’s clear I was able to get faster through endurance training.

While I never trained to heart-rate I will highlight that on Solent 1/2M I averaged 163bpm; while on my Steady run of Nov 29th I averaged 149bpm with a max of 158bpm. I certainly wasn’t pushing as hard in training as I did during the race.

On the Steady run, which was typical during this training block, I spent over fifty mins at heart-rates over 150bpm which demolishes the age-related MAF formula’s calculation that as a 46-year-old man I should have been training to a heart-rate below 134. I certainly felt no strain and there were no health consequences incurred from doing so.

The other thing to note is the benefit of the endurance work was only possible because I already had the speed. At parkrun in August my fastest mile was 6:16 and, at the half marathon it was 6:41. All the endurance training did was train the body to hold onto that existing speed for longer. This is the nature of the endurance training – faster times occur because you are more consistent in your mile splits; not because it digs out more speed. Throughout this period, I never went to the track or did any interval work; I just worked on endurance.

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