Kate Galliett is a fitness coach with a sound, evidence-based perspective on one of the most persistently confusing elements of exercise and fitness: flexibility. This brief article is worth the read. I wish people would stop talking about flexibility, which implies arbitrary (and often groundless) standards, such as can you do a split. Unless you are a gymnast, why would you need to do a split? Even more to the point, the ability to do a split likely has much more to do with genetics (limb length, muscle attachment points, etc.), which is trainable only in limited amounts, than a stretching strategy. Train to move as you need to move for your life or sport. This far more interesting and important framework develops when you talk about mobility and whether you move well enough to accomplish your exercise or athletic goals.
Studies have shown that static stretching before a workout actually DECREASES your strength and power during your workout.