The text summarizes various findings from studies comparing heart rate, % heart rate, and PO between males and females during exercise. It mentions that females generally have higher heart rates and % heart rates than males for similar %PO, and that males have slower heart rates and quicker recovery times than females. It also highlights a study showing a more gradual decline of peak heart rate with age in women. Additionally, it mentions the similar maximum heart rate between males and females, but a lower cardiac index at maximum exercise in females. The text also mentions the effects of different exercise intensities on heart rate, including a condition where the heart rate rises abruptly. Finally, it briefly mentions an older study that examined heart rate data from physically active men after exercise.