Thats your heart rate. The Karvonen formula is often used for this purpose and calculates results as a function of heart rate reserve HRR and maximum heart rate HRmax. This shows that moderate-intensity physical activity for a 50-year-old person will require that the heart rate remains between 109 and 129 bpm during physical activity.
Firstly you can measure your Pulse Rate by holding two fingers over the wrist neck or upper arm and counting the number of beats over a set period of time at least 15 to 20 seconds.
To get the most accurate reading you may want to repeat a few times and use the average of the three values. Enter the number of beats into the Heart Rate Calculator as well as the time over which you recorded your Pulse Rate. Stay seated and as motionless as possible for 5-10 minutes allowing your body to rest. Place your stopwatch or timer in a location that is easily visible.