recent studies show that stretching pre exercise does not help with injury prevention.
From a study by the National Strength and Conditioning Assoc.
“…prior stretching could reduce the number of lifts and limit the total benefit that could have been achieved. Finally, if the hypothesized neural inhibition is occurring, then prior stretching would prevent a set pool of motor units from ever being activated, and thus, a certain portion of the muscle would never get trained.”
"Substantial evidence is now available to state that static stretching can impair strength and power performance, although the duration of the impairment, the exact stretching protocols, and the physiological mechanisms are not yet known. Given the lack of evidence in favor of static stretching during warm-up for injury prevention, it seems justifiable to exclude this component from the warm-up for strength and power activities. Progressive submaximal exercise intended to increase muscle temperature and practice trials of the ensuing activity should be retained.
Some coaches have replaced static stretching with dynamic activities. For example, Rutledge and Faccioni (24) outlined warm up activities for field hockey that consisted of running drills that isolated various joints and were performed with gradually increasing intensity. When an athlete performs run-throughs at progressively increasing intensities, the joints are taken to a new ROM; therefore, the muscles are being stretched dynamically. Whether such a dynamic warm-up has the same effect as static stretching for increasing ROM or influencing the injury risk is not clear, but is worthy of examination. Further experimentation is needed before the optimum warm up protocol can be identified."