Which statement correctly describes how cardiac output changes in response to aerobic training? A) Resting cardiac output increases B) Submaximal cardiac output decreases C) Maximal cardiac output increases D) Maximal cardiac output stays the same

What this question is really asking

Aerobic (endurance) training changes how the heart pumps blood at rest, during steady (submaximal) exercise, and at maximal effort. The key is to remember that cardiac output depends on both heart rate and stroke volume.

Link cardiac output to heart rate and stroke volume

Cardiac output is: $$Q = HR \times SV$$ Training adaptations often include an increased stroke volume (more blood pumped per beat), especially at higher intensities.

What happens after aerobic training at different intensities

• Rest: Heart rate falls, stroke volume rises, so resting cardiac output usually stays about the same.
• Submaximal exercise (same absolute workload): Heart rate is lower and stroke volume is higher, so cardiac output is generally about the same (because oxygen demand at that workload is similar).
• Maximal exercise: $HR_{max}$ is usually unchanged or slightly lower, but $SV_{max}$ increases, so $Q_{max}$ increases.

Eliminating the wrong options

• A is wrong: resting $Q$ typically does not increase; it stays roughly constant.
• B is misleading: at a given workload, $Q$ is usually similar, not clearly decreased.
• D is wrong: $Q_{max}$ does not stay the same because $SV_{max}$ increases.

So, the correct choice is C: maximal cardiac output increases.