Your target heart rate during exercise depends on your age and the intensity of the activity. Here are some general guidelines from the search results:

• For moderate-intensity physical activity, your target heart rate should be about 50-70% of your maximum heart rate.
• For vigorous physical activity, your target heart rate should be about 70-85% of your maximum heart rate.
• To estimate your maximum heart rate, subtract your age from 220.
• For example, if you are 35 years old, your estimated maximum heart rate would be 185 beats per minute (bpm) .
• Your target heart rate during vigorous physical activity would be between 142 and 172 bpm.
• If you are just starting an exercise routine, you may want to start out at 60-70% of your target heart rate and gradually progress to 70-80% as you become more fit.
• You can measure your heart rate by finding your pulse and counting the number of beats in a minute.
• Fitness tracking devices or exercise machines can also calculate your target heart rate for you.

Its important to note that these are general guidelines, and your target heart rate may vary depending on your individual health and fitness level. Its always a good idea to consult with a healthcare professional before starting a new exercise routine.