Muscle Contraction
Figure 1.Myofibrils
The myofibrils are the contractile components that allow for strength and the performance
of work. When the fiber is stimulated to contract, the myofibrils experience a contractile
shortening and their circumference is increased. Myofibrils are comprised of the contractile
proteins, actin and myosin, which actually slide over each other during contractions. Heavy,
intense, low repetition resistance training has its primary effect on the actin and myosin. In fact,
the process by which damaged actin and myosin are repaired is commonly known as hypertrophy
“protein synthesis.” During heavy resistance training, the damage to the actin and myosin can
be too extensive for complete repair, or it can be insufficient to stimulate adaptation. Therefore,
the “controlled” damage and repair of them is the key to optimizing myofibril growth. This
process can be likened to the repair of skin after being injured, resulting in scar tissue which is
much stronger than the original tissue. Muscle is the same. The end result is a much larger and
stronger myofibril component.