Which statement best describes physiologic hypertrophy due to endurance exercise?

Which statement best describes physiologic hypertrophy due to endurance exercise?

• A. Has extensive fibrosis
• B. Shows an increase in myocyte length, more than width
• C. Occurs more in the right heart than the left
• D. Has less abundant capillary growth

Answer: (B)

Endurance exercise induces physiologic hypertrophy of the heart that is characterized by eccentric remodeling: the chambers enlarge and the cardiac myocytes lengthen more than they widen. This happens because the heart adds sarcomeres in series, so myocytes become longer. The result is greater chamber size and stroke volume with preserved or enhanced function, and there’s typically increased capillary density to meet the higher metabolic demand. Fibrosis is not a feature of this physiologic adaptation. Therefore, the statement describing an increase in myocyte length, more than width, best captures physiologic hypertrophy from endurance exercise. The other ideas don’t fit: extensive fibrosis is more typical of pathologic hypertrophy; capillary growth is actually increased, not reduced; and endurance adaptations affect the left and right ventricles together rather than being limited to one side.

Endurance exercise induces physiologic hypertrophy of the heart that is characterized by eccentric remodeling: the chambers enlarge and the cardiac myocytes lengthen more than they widen. This happens because the heart adds sarcomeres in series, so myocytes become longer. The result is greater chamber size and stroke volume with preserved or enhanced function, and there’s typically increased capillary density to meet the higher metabolic demand. Fibrosis is not a feature of this physiologic adaptation.

Therefore, the statement describing an increase in myocyte length, more than width, best captures physiologic hypertrophy from endurance exercise. The other ideas don’t fit: extensive fibrosis is more typical of pathologic hypertrophy; capillary growth is actually increased, not reduced; and endurance adaptations affect the left and right ventricles together rather than being limited to one side.