The terms flexibility and mobility are often used interchangeably, although in movement and sports science they refer to related but distinct concepts.
Flexibility primarily refers to muscles and is defined as the ability of muscles, tendons, and other soft tissues to lengthen passively, determining the range of motion available. Flexibility is influenced by muscle, tendon, and ligament elasticity and length, as well as the ability of muscles to relax and contract.
Mobility refers to joints. It is the ability of a joint to actively move through its full range of motion (ROM) without pain or restriction. Mobility depends not only on the flexibility of the tissues involved, but also on joint structure (capsule, ligaments, cartilage), age, sex, body temperature, strength, coordination, and balance for motor control.
Muscle flexibility is necessary but not sufficient to achieve full joint mobility.
The fascinating neuromuscular spindles
Within every voluntary striated muscle are sensory stretch receptors known as neuromuscular spindles. They detect the degree of muscle fiber elongation and transmit this information to the spinal cord and brain, playing a crucial role in motor control.
Through neuromuscular spindles, the body: perceives its position in space (proprioception), activates the stretch reflex (myotatic reflex), an involuntary contraction that resists sudden stretching.
In flexibility training, spindles activate the stretch reflex to prevent excessive muscle elongation and reduce injury risk. In mobility, they contribute to movement control, ensuring fluidity and coordination, maintaining proper muscle tone, and supporting posture.
Why train flexibility and mobility?
To increase receptor excitability thresholds, enhance neuromuscular response, improve strength and motor control, and refine movement quality and technical execution. Integrating strength and endurance training with dedicated mobility and flexibility protocols improves movement range and quality, enhances physical and athletic performance, and reduces injury risk.
Flexibility and mobility also promote proper posture, lymphatic drainage, fluid and harmonious movement patterns, and overall well-being.