There ha been some recent research on the benefits or otherwise of stretching be going running:
Stretching neither prevented or induced injury when compared to not stretching before running.Recreational and competitive running are two of the most popular athletic activities in the world. Great controversy exists as to whether runners should stretch before or after running or even stretch at all. The long established doctrine of stretching before running has been refuted by several authors, but no controlled study has supported their opinions. Stretch studies in connection with ballistic sports like weight lifting, gymnastics and wrestling suggest that a pre-participation stretch routine does not prevent injury in those sports. Those studies have been extrapolated to running and a popular notion has evolved that stretching before running is detrimental to both performance and health. Knowing whether this practice is helpful, harmful or indifferent would significantly contribute to the training habits of a great many athletes.
The authors conducted a prospective, randomized, two-arm, unmasked, comparative study of a pre-run stretch vs. no stretch in 2,729 volunteer runners. Volunteers were over the age of 13 and ran at least 10 miles per week. The study committed volunteers to three months of stretching or not stretching before running and collected blinded information via a secure website. Three stretches were described and demonstrated for the quadriceps, hamstrings, and calf muscle groups. The stretch time was three to five minutes immediately preceding running. Runners kept all other aspects of their routines the same for the three-month period. All results were self reported including compliance information. An injury was defined as a condition that prevented running for at least one week. All injuries were rigorously categorized.
A total of 1,398 (51%) out of 2,729 participants sufficiently complied with the randomized stretching assignments and completed the three-month study. This per-protocol cohort included 600 (43%) subjects randomized to the stretch group and 798 (57%) subjects randomized to the no stretch group. The raw injury rates were 16% in both groups. A total of 115 out of 220 injuries (52%) were diagnosed by a healthcare professional. Knee injuries accounted for 41/220 (19%), foot/ankle injuries 56/220 (25%), hip injuries 6/220 (3%), back injuries 10/220 (5%) and all other injuries including stress fractures, muscle tears of all types and groin pulls 105/220 (48%) of total injuries. There was a statistically significant difference in injury rate for runners who normally stretched and were randomized to the no stretch group: 40% increase in injuries (p=.05).
Over a three-month period there was no statistically significant difference in injury risk between the pre-run stretching and non-stretching groups. Stretching neither prevented or induced injury when compared to not stretching before running. Risk factors for injury during the three-month study were: BMI (the heavier the runner, the higher the risk of injury); age (increasing age, increasing injury risk); average miles per week (higher mileage, higher injury rate); history of chronic injury or injury within four months of initiating the study. Subjects who switched their normal pre-run routines were more likely to become injured than those randomized to the group adhering to their normal routine. The group most at risk were the runners who normally stretch and suddenly stopped stretching.
http://www3.aaos.org/education/anmeet/anmt2011/podium/podium.cfm?Pevent=648
http://www.runnersworld.com/article/0%2C7120%2Cs6-241-287--7001-0%2C00.html
