Life is like music; it must be composed by ear, feeling, and instinct, not by rule.

Monday, March 22, 2010

Exposure to Fatigue - A Good Thing

I've altered my training schedule pretty significantly over the past 3
weeks whereby I now do one medium intensity tempo run (about 7:15-7:45
pace) of about 3-5 miles during the middle of the week, a 10-14 mile
hard combo run (interval, tempo mix, varying paces from 6:00 - 8:30
pace) on Saturday, followed by a 10-14 mile easy run on Sunday (never
faster than 9:30 pace). This puts about 55% of my weekly mileage on
Saturday and Sunday. All the remainder of my weekly runs are easy
(never faster than a 9:00 pace) and I've cut back to 5 days of running
instead of 6 although I cover the same weekly mileage (35-45 miles per

What has been very interesting is that I've always used a "day off"
after a hard run and now I do my long easy run within 24 hours of my
long hard run. Initially I was concerned about running in a fatigued
state and, of course, the increased potential for injury. After 3
weeks, I'm actually getting stronger and adapting to the Saturday/
Sunday load.

What is also interesting is I've been spending time studying about the
pros/cons/good/bad/advantages/disadvantages to this approach and to
running while fatigued.

I found some really good information in this article:
There's a bunch of other good articles also.

Specifically, regarding the exposure to fatigue:

1. One of the most important factors that stimulate neuromuscular
adaptations resulting in greater
fatigue resistance is exposure to running fatigue. Scientists are
rapidly learning more about the
mechanisms of these adaptations. They’ve learned that a key player in
some of them is an
immune system signaling compound called interleukin-6 (IL-6). Two
factors associated with
running fatigue — muscle glycogen depletion and muscle damage — cause
circulating levels of
IL-6 to increase dramatically. In the short term, high concentrations
of IL-6 in the brain cause
exhaustion to occur. In the longer term, IL-6 coordinates many of the
body’s fitness adaptations,
ranging from increased fat burning to greater resistance to muscle

2. Another endurance-boosting neuromuscular adaptation that occurs in
response to exposure to
running fatigue is improvement in motor unit cycling. A motor unit is
a bundle of muscle fibers that
is fed by a single motor nerve. During running, only 20 to 30 percent
of the motor units in your
working muscles are active simultaneously. But it’s not the same 20 to
30 percent of motor units
that are active throughout a run. On the contrary, most of the motor
units in the working muscles
contribute to the running effort at various times over the course of a
run, but none are active all
the time. Instead, they take turns. While some are active, others
rest, awaiting their next turn.
This cycling of motor units allows you to run much farther than you
could if any of the motor units
in your working muscles were forced to remain constantly active.

The article also talks about how fatigue forces you to change your
stride and vary pace which has great advantages. By challenging your
neuromuscular system, you forces it to get creative and utilize
various patterns of muscle recruitment, "some of which will be more
efficient, others of which will
help you resist fatigue better."

I know a few of you recommended that you should run barefoot when
tired and fatigued and I think you are right (the idea that's harder
to run correctly when tired seems to be true). It's been on Sunday,
that I learn how best to run and I'm finding very efficient tweaks to
my running form. I'm also very alert given the fatigued state and the
concern of averting injury. It also forces me to spend more time
concentrating on form since I'm fatigued to run fast, which also helps
to reduce the change of injury. Conventional wisdom has been to
take a day off, after a hard run or only do a very short, easy run.
However, I'm finding the best long run is after a hard, intensity run.


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