Flexibility is defined as the measure of a joints movement through a normal range of motion. A flexible joint has the ability to move through a greater range of motion so you’re much less likely to become injured in the course of your everyday activities and sports.
Flexibility training, or stretching, improves posture. Poor postural habits can cause your muscles and the connective tissue that surrounds them to mold into the positions you maintain throughout your day, (like the rounded shoulders that develop from spending too many hours in front of a computer). Stretching these short tight muscles helps realign the soft tissue structures, so it’s a lot easier maintain good posture.
Probably the greatest benefit is the effect stretching has on the low back. By increasing the flexibility of your hamstrings, hip flexors, quadriceps, and other muscles that attach to the pelvis, you reduce the tension on the lumbar spine, so you’re much less prone to suffer from low back pain.
One more point of interest is that researchers claim stretching immediately before exercise doesn’t prevent injury; but stretching after training reduces muscle soreness, so stretch following your workouts, when your muscles are warmed up.