HeartFlex - affordable hand held exerciser - lightweight, simple to use, and effective. Like swimming, HeartFlex has one easy resistance level. Swimming and HeartFlexing become progressively more intense the longer they are performed and by increasing repetitions these activities successfully benefit everyone from beginning exerciser to elite athlete. Applications include improved muscle strength, endurance, weight loss, lower blood sugar levels, rehabilitation, and more. New technology - no springs or rubber bands.