The article discusses the difference between "tightness" and "mobility," often referred to as "tightness" as a mobility issue, as opposed to a physical limitation. Flexibility is more often a mobility one, as it allows a muscle to lengthen and move through a range of motion without actively controlling the movement. Mobility is what allows you to lower into a squat without heels lifting, press a weight overhead without arching your back, or rotate your torso without compensating elsewhere. However, this mobility is more relevant to how your body functions. Stretching can improve tolerance to a position but doesn't necessarily teach your body how to control it. Mobility also plays a central role in muscle health, performance, and long-term resilience. The article also notes that while mobility is a full-body quality, there are several areas where limitations show up, particularly in people who spend a lot of time sitting or working at a desk.