Elite Physique The New Science of Building a Better Body

Building Muscle Versus Burning Fat
59
force, which can then improve
your speed, strength, and power.
Similarly, smaller muscles are less
impressive visually, and more
often than not reduce your performance.
We usually think of those
changes in muscle size taking
place in the myofibrils. These
are the contractile elements, the
ones that generate force. But the
volume of noncontractile elements—glycogen
and semifluid
plasma—can also change. That
means two forms of hypertrophy
are theoretically possible (see
figure 4.2):
• Myofibrillar hypertrophy:
growth of the myofibrils,
which increases a muscle’s
force potential
• Sarcoplasmic hypertrophy:
increased volume of glycogen
and semifluid plasma,
which doesn’t necessarily
increase force potential
Muscle
Capillary
Muscle protein
synthesis
Amino acids
Amino acids
Muscle protein
Muscle protein
breakdown
Amino acids
Amino acids
FIGURE 4.1 Muscle protein synthesis and
breakdown. E8315/Waterbury/F04.01/670189/mh-R1
So what triggers muscle growth in the gym? Scientists have several theories
to explain how resistance training drives hypertrophy. Research by Brad Schoenfeld
(2010) suggests three possible mechanisms:
• Mechanical tension: the stress within a muscle and its supporting tissues
when it works against resistance
• Metabolic stress: the buildup of lactate, protons (H+), and inorganic phosphates
during exercise
• Muscle damage: disruption of the muscle fibers in response to intense or
high-volume exercise
Sarcoplasm
Myofibril
Original
muscle fiber
Myofibrillar
hypertrophy
Sarcoplasmic
hypertrophy
FIGURE 4.2 Myofibrillar versus sarcoplasmic hypertrophy.
E8315/Waterbury/F04.02/670190/mh-R2