If you have a lagging muscle group, the cause is more likely
neural than physiological. By "lagging" I mean a muscle group that
just doesn't seem to grow as fast as the others even though you're
training it just as hard as the rest of your body. What are the
reasons for limited muscle growth?

A) Hormonal factors: If your natural anabolic hormones
(Testosterone, growth hormone, IGF-1) are on the low side, your
insulin response is suboptimal (insulin resistance) and your
catabolic hormones are chronically elevated, then it'll be next to
impossible to add muscle mass.

B) Nutritional factors: If you don't ingest enough nutrients to
fuel muscle growth then chances are you won't be able to build new
muscle tissue. Digestive problems also fall into this category. If
you eat a lot but can't absorb all the nutrients, then it's as if
you didn't give your body enough of them to begin with.

C) Metabolic factors: Some people do have a revved up
metabolism. This is sometimes due to hyperthyroidism. When
someone's metabolic rate is high, then he might require even more
food than he should need "in theory." If you don't eat enough for
your metabolism, then you won't gain muscle.

D) Improper training: If you neglect a certain muscle group by
not training it hard enough or without enough volume, then its
growth will be slower.

E) Muscle fiber dominance: The more fast-twitch dominant a
muscle is, the better it can grow. So if a muscle group doesn't
have a large proportion of fast-twitch fibers, or if your nervous
system isn't effective at activating these fast-twitch fibers, then
muscle growth will be slower.

Reasons A to C can't explain a lagging muscle group; they can explain lack of overall growth. But if you can develop
all your muscles except for one or two stubborn groups then the
problem isn't general, so it can't be hormonal, nutritional, or
metabolic.

Reason D could explain it. If you're doing little to no biceps
work and they aren't growing as fast as the rest of your body, then
the training you perform for that muscle group might need to be
reevaluated. But if you're training your lagging muscle group just
as hard as the rest of the body, then the problem might be
elsewhere.

If a muscle is almost devoid of fast-twitch fibers, then it'll
be more growth-resistant. However, it's pretty rare to find someone
whose major muscle groups have fewer than 30% fast-twitch fibers.
And according to the work of professor Tihanyi, a muscle that's 30%
fast-twitch can become as strong and grow as much as a muscle
that's 70% fast-twitch, if trained properly.

So the real reason for the absence of growth might not be so
much the lack of fast-twitch fibers in the muscle, but rather the
relative incapacity of the nervous system to recruit the FT fibers
that are actually present in the muscle group.

Basically, to make a muscle grow you must be good at activating
that muscle! There can be two levels of activation:

Level 1: You have problems recruiting a muscle because it's your
weakest link in a chain. For example, if pecs are a weak point when
training chest, you recruit more delts and/or triceps. As a result,
the delts and triceps grow and get stronger while the pecs are left
relatively un-stimulated.

In all fairness, the pectorals are recruited, but since
the delts and triceps will do most of the work, the pecs aren't
under maximal loading. As a result, you don't recruit the
fast-twitch fibers. Over time your nervous system becomes good at
recruiting the delts and triceps but less efficient at doing the
same for the chest. In that particular case, the more "chest" work
you do, the bigger your problem becomes!

You don't need more training volume (at least not right now);
you need to work smarter to teach your nervous system how to
activate the chest. Once your nervous system is good at recruiting
the pectorals, then you can move back to regular chest work and
it'll grow optimally.

Level 2: You can recruit a muscle just fine but you have trouble
tapping into those high-threshold motor units. Once again, doing
more work (volume) isn't the answer. High-threshold motor units/FT
fibers are recruited mostly when the tension is high. Tension is
maximized either by using heavy loads or explosive movements.

Adding more volume will just create fatigue and will result in
an even greater reliance on the slow-twitch fibers. What's worse is
that over time the fast-twitch fibers that you're able to recruit
could take on slow-twitch properties.

So what can you do? The two strategies are:

Strategy 1: If you have problems recruiting a muscle because
it's getting overpowered by others when you perform an exercise,
you should use either the pre-fatigue or post-fatigue method. This
means supersetting an isolation exercise for the muscle you have
problems recruiting with your main training movement.

The isolation exercise is either placed before (pre-fatigue) or
after (post-fatigue). Normally I prefer to use the post-fatigue
technique, but an activation problem is one of the cases where I
actually prefer to use the pre-fatigue method. In that situation,
the isolation exercise serves two purposes:

1. It can improve your capacity to activate the target muscle
during the main movement via enhanced feedback. By enhanced
feedback I mean that the isolation movement will create a localized
fatigue and pump that will result in your feeling that muscle group
more during the performance of the main movement. Since you can
feel that muscle working during your set, it's easier to develop a
good mind-muscle link.

2. By creating a certain amount of fatigue with the isolation
movement, you make sure that this muscle will be fully stimulated
even though it normally doesn't receive maximum stimulation during
the multi-joint exercise.

Post-fatigue (performing the isolation exercise after the main
movement) does allow you to fully stimulate the target muscle if it
hasn't been thoroughly worked with the main, multi-joint exercise.
However, you don't get the enhanced feedback effect. That's why
when you have problems recruiting a certain muscle, pre-fatigue is
a better option: it'll allow you to develop the capacity to recruit
that hard-to-target muscle group.

Pre-fatigue isn't as effective as post-fatigue at stimulating
maximal growth because you can't use as much weight on the
multi-joint movement (because you pre-fatigued a muscle group
involved in the lift). That's why you should see pre-fatigue as a
"learning tool."

It allows you to become better at recruiting the muscle you want
to build. Before being able to fully stimulate growth in a muscle,
you must first be able to recruit it optimally! That's the reason
why pre-fatigue, which on paper is an inferior muscle-building
method, can become very effective for a specific
purpose.

Strategy 2: If you can recruit a muscle just fine but it's still
stubborn, it can mean that you have problems maximally activating
the fast-twitch fibers. Here are a few tips to help you change
that:

• Always try to lift the weight with as much acceleration as
possible. If the weight is heavy, or fatigue sets in during the
last few reps of a set, then the actual speed/acceleration might
not be very high. But neurally, the intent to accelerate is the
key. This will maximize force production at a given weight which
will facilitate FT fiber recruitment.

• Control the weight during the eccentric (lowering) portion and
opt for exercises where the target muscle is put in a stretched
position. When a muscle is stretched prior to contracting, more
fast-twitch fibers will be recruited and it increases force
production at high rates of acceleration (which also increases FT
recruitment).

• You can combine maximal functional or maximal isometrics with
regular lifting movements. You can recruit up to 10% more muscle
fibers during a maximal isometric action as during a maximal
concentric movement. Performing a maximal isometric action
immediately before a regular lifting set will also allow you to
recruit more FT fibers during the regular lifting
set.

For example:

A1. Functional isometric bench press

Use a bar weight that is around 50-60% of your maximum and push it
against the pins as hard as humanly possible for 6
seconds.

Rest 60-90 seconds

A2. Bench press

3-5 reps (heavy load)

120 seconds of rest

Perform complex 4-5 times

* Heavier weights can also be used since the more force you have
to produce, the more FT fibers you'll recruit. You don't have to
shoot for a 1RM; anything in the 4-6 reps range will do, especially
if you focus on contracting the muscle as hard as possible during
the set.

Conclusion

Hopefully I've given you enough new tricks to motivate you and your stubborn muscles. Now get thee to the
gym!