During a fixed-power, total-body aerobic program, which variable is most likely lower during lower-extremity exercise than during upper-extremity exercise?

• A. Heart rate will be lower during upper extremity exercise as compared to lower extremity exercise.
• B. Stroke volume will be lower during lower extremity exercise as compared to upper extremity exercise.
• C. Systolic blood pressure will be lower during upper extremity exercise as compared to lower extremity exercise.
• D. Rate pressure product will be lower during lower extremity exercise as compared to upper extremity exercise.

Answer: (D)

When you compare fixed-power, total-body aerobic work between legs and arms, the cardiovascular response differs because leg work uses a much larger muscle mass and tends to produce less cardiac strain at the same power output. The rate-pressure product, which equals heart rate times systolic blood pressure and reflects myocardial oxygen demand, is typically lower for leg exercise than for arm exercise. This happens because arm work tends to raise both heart rate and systolic blood pressure more than leg work, due to higher peripheral resistance and the smaller muscle mass involved.

So the variable most likely lower during lower-extremity exercise than during upper-extremity exercise is the rate-pressure product. The other options don’t fit the common pattern: heart rate is usually higher with arm work, stroke volume is typically greater with leg work, and systolic blood pressure tends to be higher with arm work.