Final answer:
The Valsalva maneuver can cause decreased ventricular contraction strength, which may lead to a drop in cardiac output and blood pressure during the concentric phase of a resistance training repetition.
Step-by-step explanation:
The Valsalva maneuver may elicit several physiological responses during the concentric phase of a resistance training repetition. This maneuver, involving voluntary contraction of the diaphragm and abdominal wall muscles with a closed glottis, increases intra-abdominal pressure. The physiological responses include a potential decrease in ventricular contraction strength, leading to a brief reduction in cardiac output and arterial blood pressure. Additionally, vascular smooth muscle may respond to this increased pressure by stretching. This does not result in the dilation of muscular arteries by endothelins, as endothelins typically function to constrict blood vessels, not dilate them.