The one choice metabolic system for both laboratory and field testing The K5 is the 4th generation of the most popular wearable metabolic system, a breakthrough in the field of exercise physiology and human performance assessment. The K5 is the most innovative and versatile metabolic system ever created. It reaps the benefits of more than 25 years of experience with metabolic systems. The extensive list of new and unique characteristics of the K5 expands the scope of metabolic testing from clinical exercise testing to performance assessment.