Monitored heart rate can be an effective motivator. Without an electronic monitor, heart rate is easiest to locate at the carotid artery, on the side of the neck rather than the wrist. Gently pressing the area with index and middle fingers, count each beat for at least 15 seconds, and multiply the number of beats by a number so that it corresponds to one minute. (For x beats in 15 seconds, multiply x by 4.)
Working heart rate, which could be anywhere from 140 - 190 beats per minute, should be monitored to make sure that it stays at a safe level. After strenuous work, heart rate should soon recover to about 120 BPM or less. Below is a chart of the appropriate ranges of working heart rate corresponding to age and resting heart rate.
WORKING HEART RATE RANGE CHART
Resting Heart Rate Age
loe30 31-40 41-45 46-50 51-55 56-60 61-65 gt65
50-51 140-190 130-190 130-180 120-170 120-170 120-160 110-150 110-150
52-53 140-190 130-190 130-180 120-170 120-170 120-160 110-150 110-150
54-56 140-190 130-190 130-180 120-170 120-170 120-160 110-150 110-150
57-58 140-190 130-190 130-180 130-170 120-170 120-160 110-150 110-150
59-61 140-190 140-190 130-180 130-170 120-170 120-160 110-150 110-150
62-63 140-190 140-190 130-180 130-170 120-170 120-160 120-150 110-150
64-66 140-190 140-190 130-180 130-170 130-170 120-160 120-150 110-150
67-68 140-190 140-190 140-180 130-170 130-170 120-160 120-150 110-150
69-71 150-190 140-190 140-180 130-170 130-170 120-160 120-150 120-150
72-73 150-190 140-190 140-180 130-170 130-170 130-160 120-150 120-150
74-76 150-190 140-190 140-180 130-170 130-170 130-160 120-150 120-150
77-78 150-190 140-190 140-180 130-170 130-170 130-160 120-150 120-150
79-81 150-190 140-190 140-180 130-170 130-170 130-160 120-150 120-150
82-83 150-190 140-190 140-180 140-170 130-170 130-160 120-150 120-150
84-86 150-190 150-190 140-180 140-170 130-170 130-160 120-150 120-150
87-88 150-190 150-190 140-180 140-170 130-170 130-160 130-150 120-150
89-91 150-190 150-190 140-180 140-170 140-170 130-160 130-150 120-150
Source: http://www.jackis.com/Heart_Rates.htm#WHR%20Chart