The terms mobility and flexibility are often used interchangeably in discussions about fitness and movement health, but they represent distinct concepts foundational to physical performance. Flexibility is a component of overall movement capacity, but it does not fully describe the functional ability to move a joint through its available space. Understanding the difference between these two attributes is important because they require separate training approaches. This clarification is essential for anyone looking to improve movement health, reduce injury risk, or enhance athletic performance.
Understanding Flexibility
Flexibility is defined as the passive range of motion (ROM) available at a joint. This passive state refers to the extent a joint can be moved with the assistance of an external force, such as gravity, a partner, or a strap, without the individual’s own muscle effort to hold the position. The degree of flexibility is primarily determined by the extensibility of the soft tissues surrounding the joint, including the muscles, tendons, and ligaments.
The nervous system regulates the muscle’s tolerance to a stretch, playing a significant role in this passive range. Sensory receptors within the muscle trigger a protective mechanism called the stretch reflex to prevent overstretching. Holding a deep, static stretch signals the nervous system that the extended position is safe, effectively increasing stretch tolerance over time. Assessing flexibility might involve using a strap to pull a leg toward the chest, which reveals the maximum passive length of the hamstring muscle.
Understanding Mobility
Mobility, in contrast to flexibility, is the active, controlled range of motion that a person can achieve using their own muscle strength. It describes the joint’s ability to move freely and easily through its full range without external assistance. Mobility requires not only adequate tissue length (flexibility) but also joint health, muscular strength, and motor control throughout the entire range.
This capacity is often referred to as usable range of motion because it reflects the body’s ability to stabilize and produce force at the end ranges of movement. If a person can touch their toes with assistance (flexibility) but cannot lift their leg as high using only their hip muscles, their mobility is limited. The nervous system is heavily involved, coordinating the contraction of muscles that move the joint while simultaneously relaxing the opposing muscles.
Specific Training Approaches
Training methods are differentiated based on whether the goal is to increase passive range (flexibility) or active, controlled range (mobility). Flexibility training focuses on lengthening tissues and increasing stretch tolerance. Static stretching involves holding a position at the point of mild tension for a prolonged period, typically 20 to 60 seconds, which helps calm the nervous system and encourages muscle elongation.
Another method is Proprioceptive Neuromuscular Facilitation (PNF) stretching, which uses alternating muscle contractions and relaxations to signal the nervous system to allow a deeper stretch. These passive techniques are generally best performed after a workout when muscles are warm and the goal is recovery and tissue lengthening.
Mobility training, conversely, is built on active control and strength within the available range of motion. Dynamic stretching, which uses controlled movements like leg swings or arm circles, is a common mobility exercise often used as a warm-up. More specialized mobility drills include Controlled Articular Rotations (CARs), where a joint is actively rotated through its largest pain-free range of motion, helping to improve joint capsule health and motor control. Loaded stretching incorporates resistance, such as weights or bands, to build strength in the newly acquired end ranges of motion, turning passive flexibility into usable, active mobility.