Dispelling Common Myths
All the tissue fibers within a motor unit will contract together because the entire motor unit
is stimulated to contract by the same neuron, regardless of the angle of resistance (innervations).
Movements should be selected that allow the target muscles to be stressed by the heaviest
amount of weight possible, calling on the involvement of the greatest number of motor units
possible (desired method of motor unit recruitment). Extremely heavy compound movements are
said to have the greatest degree of leverage and should always be used in preference to partial
isolation movements. It is important to once again realize that strict isolation is an anatomical
impossibility since one muscle group cannot function on its own. All muscle tissue fibers run the
entire length of the muscle group, from its origin to its insertion, and receive growth stimulation
uniformly throughout their entire length. With this in mind, once again, it is physiologically
impossible to shape a muscle. Muscle tissue structure and shape are strictly genetic.
Cardiac and Smooth Muscles
Cardiac muscle refers to the heart itself. Smooth muscles include digestive, respiratory
and vascular tissues. The digestive and respiratory tissues provide for the movement of nutrients
and wastes for their uptake and excretion respectively, and will not be discussed in great detail
here. Vascular tissue, or blood vessels, function in a variety of ways in response to exercise,
adrenal hormone stimulation, and sympathetic nervous system stimulation will be discussed.
Cardiac Muscle Function & Resistance Exercise
The cardiac muscle is similar in many ways to skeletal muscle. They are both striated
and house the same cellular components in varying proportion. The heart muscle will adapt to
resistance exercise in much the same way that skeletal muscles do. If the heart is forced to
pump against an increased amount of resistance for prolonged periods, such as is common in
resistance exercise, the cardiac tissue or heart muscle will most likely adapt by increasing in size
and strength.