Mr. Steele, I train at the local racquet and health club and Teddy the head trainer told me that “straining while training” is “passe” and that going to failure is a surefire way to incur injury. He suggested some Pilates and showed me a few Swiss ball movements using weights - one exercise in particular caught my attention: he sat on the big blue ball, one leg on the floor with the other leg extended in front of him, he proceeded to do one arm dumbbell presses. He said this type movement, purposefully off balance while lifting what he called, “reasonable poundage” (a 10-pound dumbbell) was superb for building core strength. Teddy is a big believer in building core strength and while he is not what you’d call physically impressive, he has a six pack (It doesn’t hurt that he looks like Tom Cruise!) and a large female following…his core strength classes are mobbed with ladies. I was wondering if you and Teddy see eye to eye on core strength training and its many benefits.

Sheri, Cambridge Mass

Fats also play an important role in energy production during prolonged exercise, but there are two problems with fat as an exercise fuel. First, it requires oxygen to be converted to energy. That means fat metabolism is limited by the rate of oxygen delivery to the muscles. Second, your muscles can store very little fat inside them, so before they can be burned by the muscle for energy, they must be transported in from somewhere else. That means fatty acid utilization is also limited by the delivery of fatty acids to muscles. And fatty acid release is a slow, complicated process that occurs only when carb stores become depleted.