Which of the following factors is NOT typically improved by cardiovascular training?

Cardiovascular training primarily focuses on enhancing the efficiency of the heart, lungs, and circulatory system. This type of training leads to various physiological benefits, such as improved aerobic capacity, better sleep quality, lower blood pressure, and increased energy levels due to more efficient oxygen delivery to the muscles and better overall fitness.

Enhanced flexibility is not typically a direct result of cardiovascular training. Flexibility is more commonly improved through activities specifically designed to enhance the range of motion in joints and muscles, such as stretching exercises or yoga. While some cardiovascular activities may involve movements that could slightly improve flexibility—like dynamic stretching during a warm-up—these benefits are not the primary focus or outcome of cardiovascular exercise. Thus, the correct answer highlights that enhanced flexibility is not a typical improvement associated with cardiovascular training.