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Law of Diminishing Returns

I remember learning about the Law of Diminishing Returns in a high school economics class. Want to know what it is?

In economics, diminishing returns (also called diminishing marginal returns) is the decrease in the marginal (per-unit) output of a production process as the amount of a single factor of production is increased, while the amounts of all other factors of production stay constant. (from Wikipedia)

And, as much as I would like it not to, it applies to my running as well.  And I know the exact point where I hit the diminishing returns.


35 miles per week.  I can run 6 days a week, add speed work or hill work and my legs and body are happy.  But, the week my miles get above 35, things start to fall apart.

And this is a problem when you are training for a marathon.

Have you read the book Born to Run?  I have, and as much as I would like to think I was born to run, I do not think I was born to run marathons. At this point my legs are on the verge of shin splints and knee problems. I am frustrated and upset.  And there are days I want to give up.

I went into this marathon training cycle fairly optimistic.  This is my second marathon and I wanted to crush my last marathon time.  I had a good base.  Legs felt great. I had PR'd in a half marathon right at the beginning of training. But now my average pace is getting slower and slower because my legs just cannot seem to handle the faster paces right now.  I am afraid that I will go into the second marathon no better off than I did in my first. I did not want to just finish another marathon. I wanted to run it well.  But, at this point, I am hoping I can get to the finish uninjured.

 Is this normal? Does every marathoner go through this? Am I doing something wrong? Am I just not meant to run marathons?


  1. I am so sorry...I haven't been following your training but is it possible that you are running too many of your runs at a faster pace and not enough slower miles? That is usually where I make the mistake and then pay for it. The vast majority of your volume should be at maintenance pace... about a min/mile or so slower than your marathon race pace. I know that I can only run 3 days a week and can only do speedwork 1x a week MAX or I start hurting. I think you could get by on 35 mi/week and still safely run a marathon. Wishing you the best! :)

  2. i realized after my half-marathon that running long distance was not an optimal form of exercise for my health.

    may God's will be done.

  3. i realized, after my half-marathon, that running long distance had an adverse affect on my health.

    it was tough to listen to my body when i so badly desired to finish my goal. it was another opportunity for me to humble myself.

    i will keep you in prayer. may God's will be done.

  4. Katie,
    I think you are so brave to have completed one, and maybe that's all you need to do?

    Just in training for our second half marathon, Phil and I have had the discussions that we are done after this. His back is always killing him, and my left knee swells up whenever I run more than 7 miles.

    We decided we are happy when we are active and make our "normal" run workouts 5 milers instead of constantly trying to increase mileage. Plus, I really miss my kickboxing and weight training classes when I am in running/training mode. I think I get a much more balanced body when I can switch up my workout everyday instead of all running all the time.

    You (and I mean we) are always so much harder on yourself than you need to be. I hope you can come to peace with your decision, whatever it may be.

  5. I don't know what training plan you are using, but are you attempting to build your mileage and your speed at the same time? If so, back off on the speed work for a bit and let your legs get used to the distance.

  6. I had this problem with my first two marathons. Got hurt right when the mileage got to about 35/week. Then I rethought my training. Went from 4 days/wk to 5 days/wk to spread out my mileage. Cut all speed work and made sure my pace was "easy." Started averaging 40-50 miles per week and stayed injury free. Dropped my marathon time from 5:06 to 4:12. I think that your plan is probably not working for your body.

  7. yes, i will say though as time has gone on my point of breakdown has gone up.. Be patient, ice and rest when you feel it. It's ok to run less one week if your body needs it. I have also noticed that I am more injury prone the week before my period. NOT KIDDING.. It's like my body falls apart, so I've learned its ok to run less that week.

  8. You are training so hard and whatever you decide will be good. Hang in there and know you have a lot of support...
    It also looks like you have a lot of good running advice as well.


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