Basic principles regarding strength, flexibility, and stability exercises.

Strength, flexibility, and stability are physiologic parameters associated with health-related physical fitness. Each of these domains affects health in general, the risk of injury, how an injury is treated, and performance in activities of daily living and sports. These domains are affected by individual phenotype, age, deconditioning, occupational activity, and formal exercise. Deficits or loss of strength, flexibility, and stability can be prevented or reduced with exercise programs. Normal muscle strength has been associated with general health benefits, increased life expectancy, psychological benefits, prevention of illness, and reduction of disability in older adults. Static flexibility programs have been shown to improve joint range of motion and tolerance to stretch but do not appear to reduce the risk of musculoskeletal injury and may impair muscle performance immediately after a static stretch. Dynamic flexibility, on the other hand, may enhance power and improve sports-specific performance. Stability training leads to improved balance and neuromuscular control, may prevent injury to the knee and ankle joints, and can be used for treatment of patients with low back pain.