Which vessel's waveforms would be expected to show a marked change with a clenched fist maneuver?

The brachial artery is the correct answer because it is directly influenced by changes in peripheral resistance and blood flow dynamics during maneuvers that involve the upper extremities, such as a clenched fist. When a patient clenches their fist, it increases the demand for blood supply to the muscles of the forearm and hand, leading to a temporary increase in blood flow through the brachial artery. This increased flow can cause changes in the waveform characteristics seen on Doppler ultrasound, reflecting the increased activity and the body’s adjustments to meet the metabolic demands of the contracting muscles.

The radial artery, while also supplying the forearm, may not exhibit as marked a change in waveform due to its more distal location in the vascular system. The popliteal and femoral arteries serve the lower extremities, where a clenched fist maneuver will likely have minimal impact on their waveforms compared to those in the upper extremities. Consequently, these vessels would not demonstrate the same pronounced changes in waveform seen in the brachial artery during this specific maneuver.