While the terms flexibility and mobility are often used interchangeably, they describe two fundamentally different physical capabilities related to movement. Flexibility describes the length of the body’s soft tissues, whereas mobility is a measure of how well a joint can be moved and controlled through a given range. A person may possess a high degree of flexibility and still have poor functional mobility, illustrating that the two concepts are not the same. Understanding the distinction between these two attributes is important for anyone looking to improve their physical performance and reduce the likelihood of injury.
Flexibility: The Measure of Passive Range
Flexibility is defined as the ability of soft tissues to elongate, determining the maximum range of motion achievable at a joint. This attribute is specific to the muscles, tendons, and ligaments surrounding a joint. Flexibility is measured by the passive range of motion (PROM), which is the extent a joint can be moved with the assistance of an external force.
An external force could be gravity, a partner, or using one’s own hand to pull a limb further into a stretch. Static stretching, where a position is held for an extended period, is the most common method for improving this passive range. The goal is to increase the extensibility of the muscle-tendon unit, allowing the joint to reach positions it could not otherwise. This lengthening is largely due to the nervous system allowing the muscle to tolerate a greater stretch, rather than a permanent change in the actual length of the muscle fibers.
Mobility: Active Control and Joint Health
Mobility is a complex physical quality involving the ability to actively move a joint through its full range of motion with coordination and strength. This is characterized as active range of motion (AROM), requiring surrounding muscles to contract and stabilize the joint without external assistance. Mobility involves the health of the joint capsule, the integrity of the ligaments, and the nervous system’s capability to coordinate movement.
For a joint to be mobile, opposing muscles must have sufficient flexibility, and initiating muscles must have the strength to pull the joint into that new range. This ability to control the movement separates mobility from simple flexibility. When a person has high flexibility but low strength and control in the end ranges of motion, they are considered unstable and may be at a higher risk of soft tissue injury.
Training and Application: Bridging the Gap
Training methods for flexibility and mobility differ significantly because they address distinct physical components. Flexibility training typically uses static stretching to target the lengthening of specific muscle groups after activity. This includes long-hold stretches lasting 30 seconds or more, aimed at increasing the passive range.
Mobility training is dynamic and focuses on integrating strength and control throughout the entire range of motion. Exercises like Controlled Articular Rotations (CARs) move a joint slowly and intentionally to improve the health of the joint capsule and reinforce active end-range strength. Loaded stretching, which involves applying light tension at the end of a range, is another method used to build strength in that newly accessible range.
The distinction between the two capacities is significant for functional fitness. While flexibility is a necessary foundation, mobility is more important for daily life and performance because it includes the element of control. Mobility requires the combination of flexibility, strength, and motor control to execute movements like standing up from a deep squat safely and efficiently. Focusing on mobility ensures the body’s entire movement system works together to execute movement with precision, minimizing compensatory patterns that lead to strain or injury.