During which phase of resistance training is stroke volume significantly increased?

The correct choice regarding the phase of resistance training during which stroke volume significantly increases is the eccentric phase. During eccentric contractions, the muscle lengthens under tension, typically while controlling the weight as it is lowered. This type of muscle action leads to increased mechanical strain on the heart and the skeletal muscle, stimulating various physiological responses.

One important response is the enhanced filling of the heart during diastole. As muscles contract eccentrically, they create a "muscle pump" effect, which assists venous return to the heart. This increased return, coupled with a higher stretch of the cardiac muscle fibers, leads to an improved stroke volume, meaning the heart pumps a greater volume of blood with each beat.

In contrast, concentric contractions, where muscles shorten while working against resistance, do not typically cause the same degree of increase in stroke volume due to the increased intrathoracic pressure that can impede venous return. Similarly, during isometric contraction, where muscles generate force without changing length, the increased pressure can limit blood flow to the heart and does not promote significant stroke volume increase. The recovery phase, although important for restoring homeostasis, does not involve the active muscular contractions necessary to elicit a significant change in stroke volume during exercise.

Thus