Racing at all distances requires sustained endurance. Long repetitions at anaerobic threshold, or "cruise intervals" as Jack Daniels Ph.D. calls them, or tempo runs, improve your ability to maintain race pace training your muscles to work efficiently, forming less lactate.

Running Book...A Sample: Chapter David Holt

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Racing requires a constant fast pace. So far, you’ve developed endur¬
ance with steady running, and some speed with short strides. Now we
will combine them as a prelude to races of a mile to 10 kilometers.


I did a few stretches and exercises with the
emphasis on getting the shin muscles warm. Despite the guru’s ad¬
vice, my speedy stride and fartlek sessions had given me shin pains in
the first two weeks. Decreasing my stride length to land softer, as if
on eggshells, combined with toe lifts and ankle rotations, had cleared
the discomfort.
	As I eased into the run I reflected on last few weeks training.
	I’ve been here every fortnight for ten weeks now. Surely ten weeks
was enough to develop speed.

“How you’ll doin’ Davey boy,” he said as I reached the five minute
point of the run. “I likes the way you start your run ladde...nice and steady like.”
He paused as I converted the words. “Don’t ever give up yer
speed-meister-work matey. I’m not a one to insult that fine animal,
but as a runner, you be a sloth. But there’s a much work we can do
for you.”
	“Have you eaten Treasure Island per chance?”
	“Yes me boy...and a good read it was as I studied the south of this
fair country.”
	“Do you think your masters will benefit from the learning?”
	He opened his left eye, then raised his right shoulder as if a parrot
had just taken flight from it saying. “Precious little, David. But I have
my coaching to keep me sane. And I’m off to Africa tonight. The
Valley of Rift.”
	“The Rift Valley you mean.”
	“Absolutely. Now then, I watched you run some of your strides.
Your arms hardly flap at all these days. How do they feel?”
	“The strides were fun...leg speed is developing. The
quadriceps objected to coming up higher, but they’re used to it now.
The hamstrings and my butt were tender after I got carried away
doing the 200s. I won’t do that again.”
	“Try not to run more than a second faster than previous running sessions
for 200s. You have years to make progress. 
	“Are the shin exercises you do effective?”
	“Yes they are. Now. What’s next?”
	“Don’t be too eager my friend. You have to think of your bones.
Osteoblasts are busy depositing a matrix which is calcifying by the
day--making your bones stronger. Osteoclasts are shaping this new
bone. Don’t rush into still harder training. First promise you will take
things gradual like.”
	He seemed to realize I meant it sincerely...despite the fact that I all
but blurted out the child like, “I promise.”
	He paused as we came to the best overlook on the course. We
looked into the green valley--home to one and a half million hu¬
mans--then continued along the trail as he told me the following. 
“To date, you’ve been running at speeds which enable you to provide
all the oxygen requirements of your body as you run. So-called 
aerobic running--the muscles working with sufficient oxygen. 
	“However, when you run fast for long periods, the oxygen system
will not be able to keep up--part of the long repetition or race will be
run without oxygen being used to breakdown all the fuel into a usable
energy source. This is anaerobic running, or running without oxygen.
	“In practice, the aerobic system will provide as much energy as it
can--only the deficit will be made up by the anaerobic system. Both
systems operate at all times, but the anaerobic system becomes more
important for sudden intense efforts, such as running fast up a hill. In
a race, the anaerobic system will be supplementing the aerobic system,
even if providing only a few percent of the total energy needs.
	“Anaerobic running produces lactic acid. The acid accumulates in
the muscles and contributes to the heavy legs feeling--the wastes
contribute to your fatigue--a factor causing you to slow down. Tele¬
vision commentators often say things like-- ‘he’s running in treacle;
rigor mortis has set in; the monkey’s jumped on his back’ about
runners in that highly anaerobic event...the 400 meters.
	“To delay this anaerobic poisoning of the muscles, I had you
develop your heart and lungs with steady running...then further
stimulate them with the strides over short distances at a moderate
	“These two forms of running have developed your aerobic system
to good effect...though it’ll be years before you reach your maximum
potential. I can’t stress how important it is to go through the first two
parts of this manual. At ten weeks each, they’ve given you an excel¬
lent base from which to proceed.
	“So David, continue to be patient with yourself.”
	Then he addressed the potential readers of this journal, saying:
	“If you have not developed decent background fitness by running
at least a month each of Part One and Two’s training sessions, or you
don’t have a history of regular running, please wait before proceeding
with the sessions in this part.
	“Those who do have the background fitness, can proceed to de¬
velop the body’s ability to run introducing sessions
that create a build up of lactic acid. The acid is not dangerous, it is
merely a natural--though to you, a slowing--by-product of fast run¬
	Looking at me as I rounded a turn on that Sunday run, he said:
 	“Your first stage is to run moderately fast for three to four min¬
utes...and do so several times within a training session. The recovery
between efforts will be a walk at first.
	Later, when you’re used to the session, you can jog. However, the
jogging should last as long as the fast part. This type of running is
quite hard on your entire body--not just your muscles.”
	He moved in close to my side and whispered in my ear.
“Running fast creates extra stresses on the body.
It’s not only the muscles that feel the strain...Joints, ten¬
dons and ligaments experience additional work. You can
lesson the strain on these parts by aiming to run re¬ control. Just like in the strides of Part Two,
land soft rather than pounding. Run on soft surfaces such
as packed dirt or sand, grass, or synthetic tracks. Run
within your own body limits. Lesson the risk of injury by
holding back.”
He moved a few feet away, surveying the track ahead of us.
	“Parts of this trail would do nicely. Another good area to run these
repetitions would be the edge of a large recreation ground. Run two
thirds of it fast and jog the other third as the recovery. Or you might
use the length of a favorite piece of road--do avoid concrete’s six to ten times harder than asphalt. 
	“It helps to use permanent start and finish points to aid your
timing. Timing reps make it easier to monitor your progress. A large
tree or the corner of a building are effective points to use.
	“After warming up for at least a mile, do the usual stretching. Run
a few relaxed 50 to 100 meter strides. Then run the first of your
three minute repetitions. Don't run too fast, but you should be feeling quite
tired by the end. Your pulse will go higher than in your previous
speedwork--85 to 90 percent of your maximum is okay; with your
good overall fitness, it should soon return to 120 per minute. Once
it’s done so, you’re ready to run again.
	“Run a second repetition while thinking about your running style.
Try to keep a steady rhythm going...especially the second half. Let the
tension go from the shoulders, maybe drop the arms a little--but keep
them moving fast and allow your legs to carry you through. 
	“The leg muscles should feel a little heavy with the wastes of
anaerobic running, but after an active rest, you should persevere with
the third repetition. 
	“This time, start a little slower. As you reach halfway, pick your
knees up to extend the stride. Don’t extend it so much, and run so fast
that you collapse on the ground afterwards. Complete the session
with a significant amount to spare. The real work will come in later
sessions, when you aim to improve your times, and reduce the rest
period--but in alternate months.
	“The first time you run this session should be after a rest day. If
you’re very stiff afterwards, you’ve overdone it. As you found with
the 200s, any new type of training is hard to judge at first. In fact, if
you think you were too fast on the first repetition, consider calling it a
day. Perhaps do half a dozen short strides to unwind. 
	“A week later you can repeat the session...maybe judge your running pace
better. As with the 200s in Chapter 4, aim for your times to improve
during a session. Don’t run a fastest time by ten seconds first, to be
followed by slow efforts. 
	“After running the above session twice, you should find yourself a
second area where you can run fast for five to six minutes.”
	“Run two efforts of this five to six
minute route or loop. Try to run the first half at close to the speed of
your three minute route...then keep it going an extra two minutes.
You will need a longer recovery period--up to ten minutes is fine. Jog
or walk to stay warm for the second effort.”
	He gave me a sly look.
	“You might like to try a 9 to 10 minute loop, but to be honest, few
runners find them palatable. Most of them think 10 minute reps take
them too close to those high plains cities.”
	“Oh really,” I said.
	“Yes. Most runners feel a ten minute rep is too close to Purgatory,
and likely to place their sanity and enthusiasm in Jeopardy.”
	“So you think six minutes of running is the maximum?”
	“I think six minutes maxes out most runners. Though I entreat you
and your friends to run 10 minute efforts one day.
	“Another problem, you see, is that long repetitions are hard work
on the body and on the mind. For this reason, long reps should be
run only once a week. Alternating the area and the length of the
repetitions will give you variety.”
	He whispered in my ear again.
“It’s far better to get faster by two or three seconds per
repetition than to go slower for each one as the session
progresses. Going faster within the session makes you feel
in control.
	“Going slower for consecutive reps makes you feel bad and un¬
comfortable...demoralizing you for future sessions of this type. You’ll
dread the sessions; then you’ll avoid this type of training. You’re
likely to experience some sessions where you slow--just use your
head to keep these to a minimum.”

“To race fast you must train fast; but this fast running must feel
relaxed. Maintain your form--be economical--like you were in Part
Two. Try to gain a sense of relaxation at what will soon be
race pace. 
	“Every time you do this session, you further train your muscle
fibers to buffer the capacity for operating in the presence of lactic
acid. You also push back the anaerobic threshold. The seven minute
miles which were at your threshold a few weeks ago, will soon be
under your threshold.
	“Some people say soreness after these sessions is due to lactic acid
remaining in the muscles.”
	“Whereas, the soreness is from micro muscle fiber tears...which
will heal and result in stronger muscles if given sufficient rest. You
could lie on the grass for half an hour after the last rep (something
you might be tempted to do if you’ve run them too fast) and all the
lactic acid would be gone...absorbed by the system. However, it’s still
better to do a cooldown to bring a steady supply of blood to the
muscles. Walking is fine if you’re too pooped to run easy--any gentle
activity will reduce the potential for stiffness.
	“As you learn how to pace yourself, the times for these weekly
reps will decrease substantially at first. The next level of improvement
will come after your buffering system has adapted--the decrease in
your times may not be as profound, but it will confirm you’re getting
training benefit from the reps. Restrain yourself from racing
them...and move onto the next chapter.”

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David Holt's second running book: 10K & 5K Running, Training and Racing.
Buy 10K & 5K Running, Training & Racing Today! ">10K & 5K Running, Training & Racing, 180 pages, $17.95, by David Holt (plus 3,000 meters, 8K, 12K and 10 mile training advice and schedules for 20-100 miles per week) at
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Recreational running: 5k racing on low mileage, 15-25 week preparation for race
5k training & racing: ONE...Running for distance
10k training...part 2: hill running
Half marathon training...Anaerobic threshold running
Long intervals at 2 mile or 5k pace to complete your training. You won't need many of these sessions, but do visit this page
Running Long reps and rest when peaking for 10Ks
marathon training for the elite or "serious" runner
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