environmentalist. 1  a person who accepts the theory that environment is of overriding importance in determining individual characteristics. 2  a person working to solve environmental problems, as air and water pollution, the exhaustion of natural resources, and uncontrolled population growth.
1 Muscle helps you with aerobic exercise. The stronger you are, the better you will be at any aerobic activity.  Weight training improves your body's muscle-to-fat ratio (you end up with less body fat and more muscle), which improves both your health and your fitness level.
In order to benefit from aerobic exercise, you need to work hard enough to increase your heart rate. Or your reason could be that aerobic exercise makes you smarter. If you ask me, #3 should be aerobic metabolisms. Spend more time outside the aerobic zone without worrying that I'm damaging muscle tissue.