I ran 18 miles last week [in preparation for an upcoming marathon]. I was scheduled for 20 miles this week, but, due to weather issues, pushed it to today. . . .I thought I was full of energy and ready to run today, and I’ve gotten to 8 and I’m burned out. I feel tired and worn out, and I’m freaking out because the marathon is so close. What do I do? Do I give my body some rest and shoot for 20 on Sunday? When I have a bad running day I get so discouraged thinking I’m doing a crappy job.
What’s happening to Corinne is that the timing of her long runs isn’t giving her enough time to recover and the results are very discouraging for her. As you see from her question, she ran 18 miles last week and then had been scheduled to run 20 this week. That means that she had planned to increase her mileage from something lower to 18 and then to 20 again on back-to-back long runs. The crash in energy is most likely due to a lack of recovery time between the two runs.
What’s really important here is the spacing (or recovery) between the longest workouts at the macro level. We talk a lot about the recovery needed on a daily basis between workouts — which we’d consider to be at the micro level” — but here we’re talking about the longer recovery cycle between our longest workouts. For a long workout of 18+ miles for most people, runners need to plan about two weeks between those runs for full recovery. When a runner attempts to very long runs in less time than that, we usually would expect what Corinne described — the runner feels great going in, but then bonks along the way. The body simply wasn’t ready to go again and decided to cut its losses.
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