I think most people have heard it...you don't ever stretch before working out, it weakens you, studies proved it....didn't they?
Well here's the thing, it's called REsearch for a reason, it means you always need to REcheck & search again to see exactly which factors are doing what & why & what happens in real world situations.
I'll briefly shoot through how we got to where we are right now. A while ago, some researchers took some people put them through some stretches (2 minutes or so of extended stretching per body part then doing an exercise like a lift or a vertical jump), the results showed 100% that you got a reduction in power output if you stretched first. End of story right? ...right? ...well no, if you are training how many of you honestly stretch for 2 minutes per body part, then immediately go to crank out your top weight? ...not me...& I'm guessing not you, in any sport or event or training situation you might start with some foam rolling, then stretch (maybe 20-30 seconds per body part), then dynamic warm-up, then hit the weight working up to the top power output over a few sets. So some bright spark actually decided to test it out as it would be in a real training session (they didn't do the foam roller work, but did either:
1/ A static stretch then a netball specific warm-up, then vertical jump & 20m sprint
2/ dynamic warm-up then a netball specific warm-up, then vertical jump & 20m sprint

They both did the sprint, vertical jump after the static & dynamic warm-up, then again after the netball specific warm-up. What was found was that directly after the stretch there was significant drop in performance directly after the static stretch compared to the dynamic warm-up, but after the netball specific warm-up there was NO DIFFERENCE IN PERFORMANCE! Hence they are saying you get a drop immediately after you static stretch, but if you warm-up after there will be no difference in performance! So you could get the benefit of static stretching pre-workout if you do a bit of a warm-up after the stretch. Again this finding will need to be checked & rechecked a few times, but it's a pretty amazing about turn in what we thought we knew about stretching & it's effect on training, none of the smart guys of the time thought to test stretching in a real world setting until now & when they did it appeared to show they were completely wrong about what happens.
You can read the study for yourself here - I'll paste the abstract below as it's quite short.
It's made me consider actually re-arranging my training to include a pre-exercise stretch just to see how it affects results, if it appears not to then it might well be a safer way to approach training as you'd be stretched, warmed-up & as injury-proofed as possible if it doesn't affect power output it can only really help you stay injury-free I think? I must admit I caught flat-footed reading this study - I really thought the pre-workout static stretch issue was done & dusted & no one even thought about doing it, before this I was pretty certain you lost strength period, but I'll certainly give it a go & see for myself what the results are I'll probably go with a:

1/ skip or similar 3-5 minutes
2/ foam rolling
3/ Static stretch
4/ specific warm-up (maybe work on mobilisation of any issues)
5/ Workout
6/ Work on any issues as a cool down

Although they may change in practice, we'll have to see?

Quote:

http://www.ncbi.nlm.nih.gov/pubmed/18768355 J Sci Med Sport. 2009 Nov;12(6):657-61. Epub 2008 Sep 3. Negative effect of static stretching restored when combined with a sport specific warm-up component. Taylor KL, Sheppard JM, Lee H, Plummer N. Department of Physiology, Australian Institute of Sport, Australia. kristie.taylor@ausport.gov.au Abstract There is substantial evidence that static stretching may inhibit performance in strength and power activities. However, most of this research has involved stretching routines dissimilar to those practiced by athletes. The purpose of this study was to evaluate whether the decline in performance normally associated with static stretching pervades when the static stretching is conducted prior to a sport specific warm-up. Thirteen netball players completed two experimental warm-up conditions. Day 1 warm-up involved a submaximal run followed by 15 min of static stretching and a netball specific skill warm-up. Day 2 followed the same design; however, the static stretching was replaced with a 15 min dynamic warm-up routine to allow for a direct comparison between the static stretching and dynamic warm-up effects. Participants performed a countermovement vertical jump and 20m sprint after the first warm-up intervention (static or dynamic) and also after the netball specific skill warm-up. The static stretching condition resulted in significantly worse performance than the dynamic warm-up in vertical jump height (-4.2%, 0.40 ES) and 20m sprint time (1.4%, 0.34 ES) (p<0.05). However, no significant differences in either performance variable were evident when the skill-based warm-up was preceded by static stretching or a dynamic warm-up routine. This suggests that the practice of a subsequent high-intensity skill based warm-up restored the differences between the two warm-up interventions. Hence, if static stretching is to be included in the warm-up period, it is recommended that a period of high-intensity sport-specific skills based activity is included prior to the on-court/field performance.