3. THE HEART heart needs a fresh supply of oxygen, and as you just learned, the lungs provide it. Once the heart uses what it needs, it pumps the blood, the oxygen, and other nutrients out through the large left ventricle and through the circulatory system to all the organs, muscles, and tissues that need it.

6. How aerobically fit can we be? The average sedentary adult will reach a level of oxygen consumption close to 35 ml/kg/minute during a maximal treadmill test (where you're asked to walk as hard as you can). Translated, that means the person is consuming 35 millilitres' of oxygen for every kilogram of body weight per minute. That'll get you through the day,

26. 1. 220-age = Max HR. 2. Subtract resting heart rate from Max HR = Heart Rate Reserve (HRR). 3. Multiply HRR times percent you want to train at. 4. Add back resting heart rate. Assuming a resting heart rate of 70 bpm, 27 years old, and 70% training range: 220 - 27 = 193 193 - 70 = 123 123 x .70% = 86 86 + 70 = 156 Please note: There's been some recent research to suggest a new way of estimating maximum heart rate. The formula is the following: Multiply 0.7 times your age Subtract that number from 208. An example if you're 26 years old is: 0.7 x 26 = 18, then 208 - 18 = 190. You'd then take 190 and plug it in as usual to the formula above. This new formula makes a slightly bigger difference as you get older.