About 7-8 years ago, I guess you could have called me a well-conditioned athlete. I was speedwalking 4.25 miles every day. Back then, my resting rate was around 54. Now that I'm older( and lazier ) I usually check in at around 75. The doctor said it's nothing to worry about. Each person is different and even if you're just nervous about something, it will increase.
The average resting heart rate for an adult is between 60 and 100 beats per minute, while well-conditioned athletes can achieve between 40 and 60 beats per minute. The maximum pulse rate is 220 minus your age, and the target for a healthy pulse rate during, or just after, exercise, is 60-80 per cent of this.
Therefore, if you are aged 50, you should aim to build up fitness gradually until you reach a target pulse rate during exercise of between 102-136 bpm (beats per minute).
If you are aged 55, your target should be between 99-132 bpm, age 60 = 96-128 bpm, age 65 = 93-124bpm, age 70 = 90-120 bpm, and age 75 = 87-116 bpm.