To set your intensity level, you need to __________. A. use your maximum heart rate, which is determined by subtracting age from
220 B. exercise for a minimum of 60 minutes each session C. increase your resting heart rate by increasing the weights you lift each week D. determine what it is by subtracting your age from 2,000 calories
The cells in the heart need a constant supply of nutrients / oxygen and to get rid of their waste products ans that why it needs its own special circulatory system.
