However, there are powerlifters
that possess muscularity compara-
ble to bodybuilders. There are also
bodybuilders who have equal or
greater strength than powerlifters.
So this still doesn’t mean there is
no relationship between strength
and size.
Muscle in Action:
Load and Contraction
Muscle has an all or nothing principle,
which means that during movement
or exercise muscle fibres are either
recruited maximally or not at all.
When lifting a weight, only the
required number of muscle fibres
to lift the weight will be recruited.
A light weight will only recruit a small
number of fibres. The remaining
non-functioning fibres will be moved
by the active fibres but will not play
any role in the lifting of the weight.
So, to recruit as many fibres as
possible, the resistance or weight
must be high or heavy enough.
All fibres are needed and more
importantly the execution of the
movement must be precise.
To achieve this contraction and
bring into play all muscle fibres they
need to be in a fully contracted
state and under significant load.
As an example of this when we
look at the squat, at the top of the
movement the muscles of the legs
can be fully contracted but there
no resistance as the weight rests
on the skeletal structure causing no
adaptive stress on the contracted
muscle. This is not to say the squat
is not an excellent movement for
growth stimulus as the loads can
be very heavy.
However a leg extension brings
all the quadriceps muscles into a
shortened contracted state, under
load. However this load is now a
great deal lighter that in the squat.
Clearly, as we all know there
is benefit in performing both
exercises. The squat creates high
load but without full contraction,
whereas the leg extension gives a
full contraction, but a lighter load.
This type of situation can be
observed throughout many exer-
cises and muscles of the body.
Muscle Fibre Types
To keep things simple, we will refer
to muscle fibre categories as slow
twitch, intermediate twitch, and fast
twitch. Slow twitch motor units
produce modest contractile force,
fatigue slowly, and recover quickly.
Because of their fast recovery
profile, these are the motor units
that might stand to benefit from
repeated exposure to stress and
fatigue. Fast twitch motor units
produce high contractile force,
fatigue quickly, and recover slowly.
Subjects who have predominantly
fast twitch fibres show marked
weakening after a single set to
failure and a long respite is required
before strength returns to its
baseline. Intermediate twitch motor
units fall between these two
extremes.
During a set to failure, with
enough resistance and correct
execution, slow twitch fibres are
recruited first. If fatigue occurs
more rapidly than the time it takes
for these slow twitch fibres to
recover, then intermediate and fast
twitch fibres will be recruited. If the
fast twitch fibres become fatigued
before any of the slower twitch
units can recover, force output will
eventually fall below the weight
being used to fatigue that muscle
and failure (the inability to move that
weight) will occur.
Recruitment is stimulating
all muscle fibres with low
momentum
Only with proper execution of
movement and adequate resistance
or weight can this recruitment take
place. Fatigue of each fibre type in
sequence, until none can produce
force (lift the resistance) cannot be
achieved if the weight is thrown,
bounced, jerks or paused in the
execution. As bodybuilder’s we are
aiming to maximally recruit muscle
and exhaust it to create stimulus
significant enough to cause an
adaptation. We are not just trying
to lift a weight. That is an external
focus, as bodybuilders we need
to shift to an internal focus.
By focusing on muscle contrac-
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