Technique and Training
It has been estimated that more than half of one's success in sprint swimming is dependent upon upper body strength. At distances from 50 to 500 yards freestyle, the individual who has the greatest strength during the pull is able to overcome more of the drag created by his/her body.
Health and Nutrition
Dr. David Costill discusses the portion of his research on athletes that deals with the optimum body shape and composition for swimmers.

The USMS website contains articles about sports medicine, health, and nutrition. This information is not intended to be a substitute for professional or medical advice on personal health matters. For personal medical advice, or if you are concerned about a medical condition or injury, see your healthcare provider for evaluation and care. The USMS website also contains articles about swim training and technique, including drills and workouts. All swimmers should be evaluated by a healthcare professional prior to beginning swim training. In addition, consult with a trained coach when introducing new technique or drills to your swim training program.