I found this on an OPO site
http://oceaniapowerlifting.org/phpBB/viewtopic.php?t=48
With this growing interest in stretching it is important to establish the best way to incorporate it into our workouts. The “best way” means that we find a way to use it that brings us closer to achieving our goals. It has always been my aim to use research to get to the factual bottom of things. I think we are seeing some new relevant research we can use.
Recently a new study was published in The Journal of Strength and Conditioning Research (2) As the title of the study so aptly states, acute muscle stretching inhibits muscle strength-endurance performance. In this study two separate experiments were conducted. In experiment 1, the hamstring strength-endurance exercise (Nautilus leg curl machine) was measured by exercise performed at 60 and 40% of body weight following either a no-stretching or stretching regimen. In experiment 2, using a test-retest protocol, a hamstring strength-endurance exercise was performed at 50% body weight on 4 different days, with 2 tests following a no-stretching regimen and 2 tests following a stretching regimen. Their findings indicated that there is a significant and repeatable decrease in hamstring strength-endurance performance using leg curls following an acute stretching treatment.
Now this is not the first study demonstrating the deleterious effects of pre-exercise stretching on strength and power. Research has shown an inhibitory effect of pre-exercise stretching on maximal strength (3,4,5,6,7,8,9,10), vertical jump performance (11,12,13,14,15), and sprinting (16,17). Despite all this evidence, people, including exercise professionals and coaches still think pre-exercise stretching is critical. Old habits die hard, especially in the word of coaching.
So my point in pointing out all this evidence that if you want to incorporate stretching into your routine for the purpose of increasing a growth stimulus, there would obviously be a good and not so good time to do it. I hear a lot of people saying that they are adding stretches after each set. This would not be the best time to use loaded stretching in that it may compromise your strength and prevent you from getting in as much volume at a given weight as you need. The best time to do your stretching would be after the last set for any given muscle group. And as always, use caution when stretching vulnerable joints such as shoulders.
References:
1. Thacker SB, Gilchrist J, Stroup DF, Kimsey CD Jr. The impact of stretching on sports injury risk: a systematic review of the literature. Med Sci Sports Exerc. 2004 Mar;36(3):371-8.
2. Nelson AG, Kokkonen J, Arnall DA. Acute muscle stretching inhibits muscle strength endurance performance. J Strength Cond Res. 2005 May;19(2):338-43.
3. Avela, J., H. Kyrolainen, and P.V. Komi. Altered reflex sensitivity after repeated and prolonged passive muscle stretching. J. Appl. Physiol. 86:1283–1291. 1999.
4. Behm, D.G., D.C. Button, and J.C. Butt. Factors affecting force loss with prolonged stretching. Can. J. Appl. Physiol. 26:261–272. 2001.
5. Evetovich, T.K., N.J. Nauman, D.S. Conley, and J.B. Todd. Effect of static stretching of the biceps brachii on torque, electromyography, and mechanomyography during concentric isokinetic muscle actions. J. Strength Cond. Res. 17:484–488. 2003.
6. Fowles, J.R., D.G. Sale, and J.D. MacDougall. Reduced strength after passive stretch of the human plantarflexors. J. Appl. Physiol. 89:1179–1188. 2000.
7. Kokkonen, J., A.G. Nelson, and A. Cornwell. Acute muscle stretching inhibits maximal strength performance. Res. Q. Exerc. Sport. 69:411–415. 1998.
8. Nelson, A.G., J.D. Allen, A. Cornwell, and J. Kokkonen. Inhibition of maximal voluntary isometric torque production by acute stretching is joint-angle specific. Res. Q. Exerc. Sport. 72:68–70. 2001.
9. Nelson, A.G., I.K. Guillory, A. Cornwell, and J. Kokkonen. Inhibition of maximal voluntary isokinetic torque production following stretching is velocity specific. J. Strength Cond. Res. 15:241–246. 2001.
10. Nelson, A.G., and J. Kokkonen. Acute ballistic muscle stretching inhibits maximal strength performance. Res. Q. Exerc. Sport. 72:415–419. 2001.
11. Church, J.B., M.S. Wiggins, F.M. Moore, and R. Crist. Effect of warm-up and flexibility treatments on vertical jump performance. J. Strength Cond. Res. 15:332–336. 2001.
12. Cornwell, A., A.G. Nelson, G.D. Heise, and B. Sidaway. The acute effects of passive muscle stretching on vertical jump performance. J. Hum. Movement Stud. 40:307–324. 2001.
13. McNeal, J.R., and W.A. Sands. Acute static stretching reduces lower extremity power in trained children. Pediatr. Exerc. Sci. 15:139–145. 2003.
14. Young, W., and S. Elliott. Acute effects of static stretching, proprioceptive neuromuscular facilitation stretching, and maximum voluntary contractions on explosive force production and jumping performance. Res. Q. Exerc. Sport. 72:273–279. 2001.
15. Young, W.B., and D.G. Behm. Effects of running, static stretching and practice jumps on explosive force production and jumping performance. J. Sports Med. Phys. Fitness. 43:21–27. 2003.
16. Nelson, A.G., N.M. Driscoll, D.K. Landin, M.A. Young, and I.C. Schexnayder. Acute effects of passive muscle stretching on sprint performance. J. Sports Sci. In press.
17. Siatras, T., G. Papadopoulos, D. Mameletzi, V. Gerodimos, and S. Kellis. Static and dynamic acute stretching effect on gymnasts' speed in vaulting. Pediatr. Exerc. Sci. 15:383–391. 2003