To determine your training intensity first establish your maximum heart rate by taking 220 minus your age.

Next find your resting heart rate by checking your rate after
you’ve been resting for 15 to 20 seconds.

To determine your heart rate reserve-subtract your resting heart rate from the maximum rate.

To calculate your training intensity at 70 percent multiply the
heart rate reserve by 70 percent then add the resting heart rate
to these numbers. For the average person who is a couch potato
they could just take 220 minus their age and multiply that by
70-75 percent.