Aerobic Deficiency Syndrome (ADS) is one of the most common athletic issues we see in those people who work with us for coaching and training. It’s not a disease, so don’t worry about that. It’s a term first coined by Dr. Phil Maffetone in the 1980s. It’s a reversible condition that results from doing too much anaerobic or high-intensity exercise. People who exhibit it often have high-level anaerobic capacities from years of working out at these higher intensities. They feel athletic, fit, fast, and strong. But their aerobic base is completely underdeveloped—even non-existent.