FOREWORD During the past 10 years, a tremendous explosion of knowledgehas occurred in the exercise and sport sciences. New theories in thecoaching and training of athletes have emerged, technological break-throughs have allowed a better understanding of how people performand adapt to the stress of exercise, and we now have a better under-standing as to how exercise can improve both the quality and quantityof life. In addition, the population of the United States has becomemore conscious of physical fitness and has started exercising on theirown, with little or no knowledge of what to do or how to go about it.Consequently, many commercial enterprises have evolved to satisfy this basic consumer need. Although many of these enterprises have provided valuable consumer services, there are many others that have not had the consumer's best interests at heart and have taken advantage of the general lack of knowledge of the average consumer. In 1973, the American College of Sports Medicine, at the suggestion of their former President, Dr. Howard G. Knuttgen, planned a series of volumes to help bridge the widening gap between the latest re- search in the exercise and sport sciences and the consumer. The purpose of this Series was to bring to the level of the average consumer, the facts and basic information related to exercise in general, and individual sports specifically, in an interesting and unbiased manner. Dr. David L. Costill, currently President of the American College of Sports Medicine, was asked to initiate this Series.vii