Compound Interest and New Distances- Keeping Goals Positive & Realistic

In January 2012 I signed up for my first ultramarathon- the North Downs Way 50 miler which was scheduled to be held in August. I had already run two marathons and I had my third coming up in April where I wanted to run under 4 hours for the first time.

I remember in my registration pack I received a sticker of the digital finishing clock, where you could pull tabs off to show the time you wanted. It then stuck to your fridge for you to look at each day. I pulled the tabs on mine to not show my London goal, but my North Downs goal. I looked at 09:30 every day for 8 months in the build up to that race.

But why did I have 9 hours and 30 minutes in my head? Well, my previous best London Marathon was 4:30 in 2011. So I thought, well if I can run a marathon in 4:30 then add half an hour for the second 25 miles to another 4:30 (to factor in slowing down) and I will finish in 9:30. Simple.

What I hadn’t considered was the principal of compound interest. Only not in a good way, like with your pension.

The deadly compound interest.

The deadly compound interest.

To define compound interest I have pulled the below from Wikipedia:

Compound interest is interest added to the principal of a deposit or loan so that the added interest also earns interest from then on. This addition of interest to the principal is called compounding. A bank account, for example, may have its interest compounded every year: in this case, an account with £1000 initial principal and 20% interest per year would have a balance of £1200 at the end of the first year, £1440 at the end of the second year, £1728 at the end of the third year, and so on.

In a similar vein if you were playing 18 holes of golf and someone gave you £1 on the first hole and doubled the amount on every hole so it was £2 on hole 2, £4 on hole 3, £8 on hole 4 and so on, how much do you think you would have by hole 18? £200? £400? The answer is a staggering £131,072.

Now, from my limited experience running ultramarathons, each time I build up to a new distance is like compound interest, but not in a good way. Each and every mile after my previous longest distance felt like I was compounding the miles I had already run.

Back in August 2012, because I had no idea what I was in for- every mile over mile 26 was new to me, I ended up coming away from that run disappointed as I finished over two hours off my time goal but also missed the sub 11 hour qualification zone to go into the Western States lottery.

Instead of coming away elated that I had just done something epic- and running 50 miles across hills for the first time is epic- I came away deflated.

OK, this isn't me, but you don't want to finish your first race feeling like her. Photo:

OK, this isn’t me, but you don’t want to finish your first race feeling like her. Photo:

The same thing happened when I built up to my first 100 mile race. Again this was at the North Downs, but is still the only race I have ever dropped from of any distance. I had set myself a goal of sub 24 hours and when this was slipping away, my mind did as well. And you can’t run 100 miles if the mind isn’t with the legs on the journey.

But- once I knew these distances, I knew the pain and I bettered them. I returned to the North Downs 50 and took an hour and a half off my time. I then ran a personal best a year later at the South Downs 50 taking another hour and a half off my time. All because I knew what to expect. I knew the pain, I knew the food, I knew the strategy and I knew what the compound interest would do to me. It became familiar. The same applied to my two 100 mile races so far. My last 100 mile race in December was six hours faster than the first. Yes, the course was easier- but mainly I just knew what to expect from my body and the pain.

I wanted to write this post for a number of reasons. I know a lot of people are using the South Downs Way 50 on Saturday 4th April to run 50 miles for the first time and I want those people to feel elated when they finish, not disappointed like I did. Don’t set a time goal for a new distance, just finish it- it will be a PB anyway. And once you’ve run that distance and know what to expect, better that time at another race or return a year later.

And if you must set a goal, double your marathon time and then add a third as the bare minimum. i.e. if your P.B. to date is 4 hours at a road marathon, double this to 8. Multiply by 0.33 and add this 2.64 to the 8. 10:30 would then be the very best to shoot for, but even then this is a lofty goal. Just finish.

Only the very elite build up to a new distance with a competitive goal. One example is Stephanie Howe at Western States last year who not only won the race, but it was her first 100 miler. I have mid-pack stamped all over my forehead and that sort of thing doesn’t happen to people like me. Obviously I don’t mean the win, I mean setting a time goal for a new distance and achieving it. The real goal for most of us with a new distance should simply be getting it done.

And the compounding gets worse the longer the distance. If you want examples of this, read race reports such as Sam Robson’s from the 145 mile Grand Union Canal Race last year or Victor Ballesteros from the Tahoe 200 mile race. Every time the distance steps up, the compounding does too, so go easy on yourself and flip the pressure to positive as opposed to inevitably missing out on your time goals.

As Ultrasportslive.Tv use as their motto, “Every Finish Is Amazing”. Most people will never run an ultra and you may well forget your time in the future from your first race. But you’ll never forget crossing the finish line at a new distance.

Harvey Lewis Finishes Badwater. Now, that's a finish. Photo:

Harvey Lewis Finishes Badwater. Now, that’s a finish. Photo:


About fromsofatoultra

In August 2011 I heard the term 'Ultramarathon' for the first time and have been obsessed ever since. I am not a race winner but hope to inspire as I have been inspired- I am by no means a natural athlete and if I can do it, anyone can. Having completed my first ultra in August 2012 I have just got started...and I am here for the journey.
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1 Response to Compound Interest and New Distances- Keeping Goals Positive & Realistic

  1. Pingback: Ultramarathon Daily News, Thurs, Mar 26 - UltraRunnerPodcast: Ultramarathon News, Podcasts, and Product Reviews

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