Type of Contraction and Exercise Duration

The Thib System

Basic Principles Behind My Updated Training

We knew
we were looking at something special when we opened the huge
honkin’ file in our inbox. For us training wonks, articles
like this one that discuss the science behind training (along with
giving us incredibly useful information) are pure heaven.

was, this article, at over 7,000 words, was a bit too much heaven.
So, in order to spare your gray matter (and we’re not
talking about your underwear) and keep our servers from blowing up,
we’ve split this article into 4 parts.

This is
part 2. You can find part 1 here.

– The

Principle #3: Keep Your
Training Sessions Under 60 Minutes

Cortisol is a stress
hormone that’s released during bouts of training. Some is needed,
but too much cortisol, especially if it stays elevated after the
training session, can greatly decrease muscle growth and strength

Cortisol is catabolic,
meaning that it leads to the breakdown of stored substrates. During
exercise, this can be useful since it’ll breakdown stored glycogen
into glucose and stored fat into fatty acids to provide energy for
the working muscles. However, post-training it’ll continue to
breakdown glycogen which slows recovery. It also breaks down muscle
tissue into amino acids, making it harder to add muscle

<!– Molecule –>

Furthermore, since both
cortisol and Testosterone are both made from the same raw material
(pregnenolone), constantly elevated cortisol levels will eventually
lead to lower Testosterone levels.

Cortisol output during
training has been correlated with training volume; the more work
being done during a session, the more cortisol is produced. This is
especially true when metabolic-type training (high reps, short rest
intervals) is used.

To avoid overproducing
cortisol, you want to keep your sessions short, around an hour or

Another reason to avoid
long sessions is related to mental focus. Regardless of how much
you love training, at some point your focus will go in the crapper
during a long session. The work performed in that state will be
unproductive and could even lead to bad habits that’ll screw you in
the long run.

You can train more than one
hour per day, but split your daily volume into two workouts. In
fact, splitting your daily workload into several shorter sessions
is much more effective, as it leads to both lower cortisol
production and higher Testosterone levels. It’s been shown that
when two daily sessions are used, Testosterone production is higher
after the second workout than after the first.

When training twice a day,
it’s best to train the same body part(s) during both workouts. I
like to take this opportunity to train different types of
contractions or goals on both occasions. For example:

Option 1: Muscle Building

AM: Compound
PM: Isolation

Option 2: Strength and Size

AM: Heavy lifting (2 to 6
PM: Moderate loading (8 to
12 reps)

Option 3: Muscle Building
or Strength Emphasis (Depending on AM Load)

AM: Concentric/regular
PM: Eccentric

Option 4: Performance

AM: Explosive
PM: Heavy

Option 5: Powerlifting or
Olympic Lifting

AM: Competition
PM: Assistance

It’d be a mistake to
immediately jump to the maximum amount of training you can do with
two-a-days. There should be a progression toward that amount of


Session 1

Session 2


40 to 50 minutes

20 minutes


40 to 50 minutes

20 to 30 minutes


40 to 50 minutes

30 to 40 minutes


50 to 60 minutes



50 to 60 minutes

20 to 30 minutes


50 to 60 minutes

30 to 40 minutes


50 to 60 minutes

40 to 50 minutes


50 to 60 minutes


To judge if a
workout was productive, but not excessive, look for three

1. At the end of the workout you’re tired but
not drained.

2. You feel a pump in the trained muscle. The
intensity of the pump will obviously depend on the type of training
that you did, but you should feel the muscles that were

3. Two to three hours after the completion of
the session you should yearn for more training. If you’re still
tired or lack motivation to train after this amount of time,
chances are the session was excessive.

Principle #4: Contraction Type Depends on the

This goes hand-in-hand with the first
principle mentioned. There are basically three ways of executing a
movement when it comes to the speed of execution/type of

1. Constant tension movement: You never
release the contraction of the target muscle group during the
execution of the exercise. Basically, the muscle you’re trying to
stimulate must be kept maximally flexed for every inch of every rep
of every set. Never let it relax, not even between each rep!

The goal of this type of contraction is to
prevent blood from entering the muscle during the set. This creates
a hypoxic state because oxygen can’t enter the muscle. It also
prevents metabolic waste (lactate, hydrogen ions, etc.) from being
taken out of the muscle during the set. Both of these factors
increase the release of local growth factors like IGF-1, MGF, and
growth hormone which will help stimulate growth.

By the way, the use of isometric contractions
also falls into this category.

2. Accelerative concentric, controlled
In this type of contraction, you’re trying to accelerate
during the actual lifting portion of the movement and lower the
weight under control. You go to the exercise’s full range of
motion, but you briefly pause (around one second) between the
stretch position and the following lifting action. This short pause
will negate the contribution of the stretch-shortening cycle to the
force production.

You see, three things can contribute to
producing force when you’re lifting a weight: the actual
contraction of the muscle, the activation of the reflex known as
the stretch-shortening cycle (also called the myotatic stretch
reflex), and the fact that muscle tissue is elastic, much like a
rubber band.

When trying to maximize the amount of actual
work the muscle itself must perform, you want to minimize the
action of both the stretch reflex and the elastic contribution of
the muscle’s structure. By doing a simple one-second pause before
lifting the weight, you can accomplish that and thus maximize the
amount of force that the muscle must produce.

<!– Triceps –>

When you’re lifting the weight, try to contract the muscle as
fast as you can. This doesn’t mean focusing on lifting the bar as
fast as you can. Rather, it means that you should attempt to tense
the muscle as hard as possible right from the start of the lifting
motion. This will maximize the recruitment of the highly trainable
fast-twitch fibers.

Finally, when you lower the weight, do so
under control. The eccentric portion of the movement is where most
of the muscle damage occurs (micro-tears of the muscle fibers) and
is a powerful growth stimulus.

3. Using the stretch reflex: With this type of
lifting, you want to involve the stretch reflex and elastic
component of the muscle. Thus, you want to lift the load as fast as
possible. This explosive lifting will improve the capacity, over
time, of the nervous system to recruit the fast-twitch fibers.

It isn’t effective by itself to stimulate
maximum growth in those fibers because you can’t fatigue them
sufficiently (the time of contraction and duration of the muscle
tension per rep is too low). But by lifting this way on some
movements, you’ll become better and better at activating the
fast-twitch fibers. When you’re more efficient at doing that, every
single other exercise becomes more effective.

So, when do you use each technique?

Every time you do an isolation exercise, use
constant tension. Every time! The goal of an isolation exercise is
to completely focus the stress on the target muscle. You want a
maximal local effect, and to do that you need constant tension.
Without constant tension, isolation exercises are pointless. This
is actually one of the main reasons why isolation movements get a
bad rap. People don’t know how to do them properly, and as a
result, they end up not being effective at stimulating growth. But
when done using constant tension, they’re very effective at it.

Don’t try to use constant tension lifting with
compound movements. Not that it’s impossible, but it’s a waste of
time. The goal of a compound movement is to overload several
muscles. By nature, you can’t isolate a muscle during a multi-joint
exercise, and attempting to do so will make the exercise much less
effective than it should be.

<!– dips –>

With regular compound movements, you want to
use the second technique: accelerative lifting, short pause in the
stretch position, and a controlled eccentric. This will magnify the
hypertrophic effect of the big movements by overloading the
involved muscles as much as possible.

Finally, the explosive lifting is best kept
for exercises such as the Olympic lifts, plyometrics, and various
jumping drills and throws. While these movements won’t directly
build mass, they’ll improve your capacity to stimulate growth by
improving your neural efficiency to recruit muscle fibers.

isn’t the end of the line. There are still plenty of principles to
cover. Part 3 of Thib’s opus magnum will explore ideal
training frequency and proper rest intervals.

Christian Thibaudeau specializes in building bodies that perform as well as they look. He is one of the most sought-after coaches by the world's top athletes and bodybuilders. Check out the Christian Thibaudeau Coaching Forum.