Which of the following can cause the valsalva effect?

The Valsalva effect is primarily caused by holding one's breath during exertion. When an individual holds their breath while exerting force, such as during lifting weights, intra-abdominal pressure increases significantly. This increased pressure can affect heart rate and blood flow, leading to a temporary rise in blood pressure followed by a drop when the breath is released. The physiological basis for this reaction involves the thoracic cavity's pressure changes, which influence venous return and cardiac output.

The other options provided do not typically induce the Valsalva effect. Dynamic stretching is focused on preparing muscles for activity and does not involve breath-holding. Long-duration aerobic training generally encourages steady breathing patterns to optimize oxygen delivery and energy production, and exercising immediately after a meal might lead to discomfort but does not inherently create the conditions for the Valsalva maneuver.