Running, biking and other aerobic activity are great for your heart, but they are not enough! The latest news from exercise physiologists says, aerobic training is being oversold at the expense of muscle building. One sports physiologist with the U.S. Olympic Committee, says a lot of superb runners can't even carry their luggage across the airport, because they have so little upper body strength. Weight training is essential to maintain muscle strength, particularly as you get older. Our bodies contain approximately 650 muscles. 65% of those muscles are above the hips, an area virtually untouched by most aerobic exercise. Studies show that most people lose 30-40% of their strength and 10-12% of their muscle mass by age 65. This loss can be prevented by weight resistance training. So, yes, pumping iron really is worth the effort!