This is all based on a completely unscientific experiment with a sample size of one (me), no control group, no separation of variables, no underpinning research. In other words, it is entirely anecdotal.
When I trained for a marathon over last winter, I became (like many folks training for a marathon) very good at running long distances slowly. During the last five months’ training, I ran a total of just over 1,100 km, and my average pace dropped from 6:57 min/km in December to 7:27 min/km in April. In the same period, my average heart rate dropped from low zone 3 to high zone 2. So in other words – the many long, slow runs made me slow down further, and my body became more efficient at running slowly.
A week before the marathon (i.e., in the last week of the taper where my body would have recovered from the long training runs), I ran my last gentle 5 km at an average 6:44 min/km with 25% of the time spent in zone 3 and 75% in zone 2.
After the marathon I adopted the 80/20 principle explained in Matt’s Fitzgerald’s book of the same name. I’ll save you the time reading it; it can be boiled down to:
- Many successful athletes spend 80 of their training time at a comfortable low heart rate (which can either be defined as lactate threshold 1 (LT1) or more pragmatically the effort level that still allows the athlete to have a conversation using full sentences without struggling for breath) and the remaining 20% training hard.
- The principle works because low effort levels facilitates mitochondria growth, and that boosts stamina. High effort levels facilitates increased speed and LT2 improvements.
- The middle ground (zone 3 in typical HR based training) is bad and should be avoided – it’s too fast to be gentle enough to recover quickly, and yet too slow for significant speed improvement.
- There are exceptions to every rule, and during periods of consistent volume increase (such as when training for a full or half marathon) it might be better to change the 80/20 to 90/10.
Over the last five months from June to October I have run just under 1,000 km. So not quite as much as during the pre-marathon training, but the difference is only about 10%. However, rather than focusing purely on long, slow steady runs, I have created a more varied weekly cycle, which includes
- one hard interval session each week. It started with 200 meter intervals, when that wasn’t too challenging I changed to 400 m, then to 600 m, and I hope to push it to 800 m and eventually 1,000 m intervals over the coming months;
- one long slow run every other weekend, and a “long slow with fast finish” the other weekends. Initially the “long slow with fast finish” was for instance 21 km with 3 km at 10 km-pace at the end, and currently it’s 24 km with the last 9-12 km at HM-pace;
- the rest being gentle shorter runs in zone 2.
I track how much time is spent on “hard” running and how much is spent on “gentle”, and try to ensure that the average over a rolling 4 weeks period remains as close to 80%/20% as I can.
The big question is obviously: Does it work? Has it been worth it? The answer is Without a doubt. Yes.
I have managed to improve both my 10 km PB (by 3 minutes) and HM PB (by 16 minutes) and ticked off a couple of long-desired milestones, and I don’t think that would have been possible without the speed focus every week. Despite the increased speed, I have been injury free (which, given my bad Achilles tendon that has haunted me for a few years, is a very welcome improvement).
However, more important than race pace (given that it’s long, slow runs I love) is the improvement at the other end of the scale on the slower runs. For instance, on yesterday’s 5 km run I averaged 5:46 min/km with heart rate firmly in zone 2. That’s a full minute per km quicker than six months ago with a more relaxed heart rate. What’s not to love?
So I have become a convert and a believer in the principle. And although there’s quite a bit of fluff and filler in Fitzgerald’s book, I highly recommend it and the 80/20 principle.
Stop beating myself up
London Marathon 2018
