Another reason why its a no no
Experience in resistance training does not prevent reduction in muscle strength evoked by passive static stretching.
ABSTRACT: This study examined whether passive static stretching reduces the maximum muscle strength achieved by different body segments in untrained and resistance-trained subjects. Twenty adult men were assigned to one of two groups: untrained (UT, N = 9) and resistance-trained (RT, N = 11). The subjects performed six one-repetition maximum load (1RM) tests of the following exercises: horizontal bench press, lat pull-downs, barbell curls, and 45o leg press. The results achieved in the last two 1RM tests were used for statistical analysis. A passive static stretching program was incorporated prior to the sixth 1RM test. The body fat content was significantly higher in the UT group compared to the RT group (P < 0.0001). Moreover, the RT group showed significantly higher proportion of lean body mass compared to the UT group (P < 0.0001). Maximum muscle strength on all four exercises was significantly reduced in both groups after stretching (P < 0.01). Furthermore, the magnitude of muscle strength reduction was similar for the UT and RT groups. The exception was for barbell curls, in which the muscle strength depression was significantly higher in the UT group compared to RT group (P < 0.0001). In conclusion, the passive static stretching program was detrimental to upper and lower body maximal muscle strength performance in several body segments. The negative effects of stretching were similar for subjects participating in resistance training regimens.