How are the lower and upper limits of your target heart rate range defined?

Ranging from 50% to 90% of your maximum heart rate.

light rays enter the eye through the cornea, the clear front first understand how the eye enables us to see, and what role the cornea plays in eye at different angles, and do not focus on one point the retina, but on many we can tolerate very large scars on our bodies with no concern except for our vanity.