Figure 3.10 Types and locations of muscle architecture.
Clinical Connection 3.3
Strength training consists of exercises using high resistance with a low number of repetitions. Because increases in strength are specifi c to the type of activity performed, programs typically consist of both con- centric and eccentric work. Responses to this type of training include hypertrophy of muscle fi bers resulting from an increase in protein synthesis. The hypertro- phy results in an increase in the cross-sectional area of the muscle. The greatest changes in fi ber size are seen in type II muscle fi bers. Changes within the nervous system also contribute to this gain in strength.
Conversely, when a muscle is immobilized or unable to function, loss of strength occurs rapidly. This decrease in strength begins immediately with a 3% to 6% loss per day during the fi rst week of inac- tivity. By the second week, a person can experience a 40% to 50% reduction in strength. Along with loss of strength, muscles begin to atrophy. The decrease in muscle fi ber size and cross-sectional area of the muscle refl ects a decrease in protein synthesis of all muscle fi ber types.
