The results of this study demonstrate that 6 different 30-second static stretches of the throwing shoulder did not have a significant effect on pitching performance in collegiate baseball players. This finding supports the original hypothesis. Pitching velocity measures were not significantly altered when static stretching was included after the baseball team's active warm-up. In the SS condition, pitchers were significantly more accurate than position players. Although position players tended to have higher accuracy scores after the NS condition compared with SS, these differences did not reach statistical significance.
Some studies have shown that pre-event static stretching significantly decreased performance in activities such as sprinting (10,12,13,21) and vertical jump (3,11,29,30,34). These decreases in strength and power performance have often been attributed to increased MTU compliance or changes in neuromuscular properties. Due to time constraints, no data were collected in the present study to address these mechanisms. Because pitching performance was not significantly affected in this study, it may be assumed that any changes in MTU compliance or neuromuscular properties brought on by acute static stretching were not significant enough to affect pitching performance. The rest period between the warm-up and performance testing may have also been a major factor. The rest period in the present study was designed to replicate the amount of time baseball players typically have between the end of the warm-up and beginning of the game. Torres et al. (27) suggested that physiological responses to acute static stretching may dissipate after a rest period of 5 minutes. The present study included a rest period of 5-10 minutes, similar to the rest period allowed by Torres et al. (27). Further research is needed to determine the amount of time needed for acute static stretching-induced physiological responses to fade.
The volume and intensity of static stretching applied to a muscle group can have a significant effect on performance. Several studies have demonstrated that a static stretching volume of only 30 seconds is sufficient for producing a significant increase in joint ROM without significantly decreasing power or strength performance (23,36,37). Not only does a static stretching volume of 1 minute or more significantly decrease strength and power performance but also does not appear to significantly improve joint ROM beyond what is accomplished with 30 seconds of stretching. Although the total volume of static stretching performed in the present study was longer than 30 seconds, each of the 6 static stretches were only performed once. This volume may still be considered relatively low because many muscles are involved and several different actions occur at the shoulder joint during the overhand throwing motion (31).
Studies involving throwing or kicking movements have shown that acute static stretching did not significantly affect performance in a medicine ball toss (10,11,20,27) or football punt (35). Young et al. (35) concluded that short-term changes in flexibility brought on by static stretching would not significantly alter the performance of a skill that involved complex neuromuscular patterns of a number of muscle groups. After finding that acute static stretching did not significantly change overhand tennis serve performance, Knudson et al. (16) suggested that high-speed movements may not be significantly affected by pre-event static stretching. The results of the present study appear to support these positions.
Several limitations existed in the present study. First, only 10 fastball pitches were recorded in each testing condition. Starting pitchers may throw over 100 pitches during an actual baseball game and not all of them will be fastballs. It may be difficult to extrapolate the results of this study to a game situation. Additionally, throwing velocity and accuracy are not the only factors that determine pitching performance. Another limitation of the study was the low sample number. Because performance testing was completed during team practice to simulate a normal pre-game warm-up, fewer subjects were available to participate in the study. Larger sample sizes may have increased the probability of finding statistical significances, especially in accuracy measures. An attempt was made to determine how worthwhile the results of the present study were by using Cohen's ES as recommended by Hopkins (14) when interpreting results of athletic performance research. Small ESs in the results of the present study confirm a lack of a practical effect to go along with the lack of statistical significance seen in throwing velocity in all subjects and accuracy in pitchers. Although throwing accuracy in position players did not reach statistical significance (p = 0.07), a strong ES (ES = 0.94) indicates that a practical effect likely exists when position players throw for accuracy after acute static stretching of the upper body. It may have been useful to measure joint ROM in this study, but previous research (23,36,37) suggests that applying 1 stretch for 30 seconds produces a significant increase in joint ROM. Because each stretch was performed to the point of mild discomfort, the stimulus should have been adequate to produce an acute change in joint ROM.
Last, the static stretching protocol in this study may not have stressed the upper-body muscles enough to significantly affect throwing. The static stretching exercises used in the present study were applied only to the throwing shoulder, but the baseball pitching motion involves movement of the entire body. Wilk et al. (31) explained that the overhand throwing motion involves a kinetic chain, where energy is transferred from the legs and trunk to the throwing arm to execute the movement. Different results may have been found if static stretches were applied to the lower body and the throwing shoulder because most of the force production during the pitching motion would occur earlier in the kinetic chain. The aim of the present study was to analyze the effects of acute static stretching on upper-body muscles, so the leg muscles were not stretched. Time constraints also limited the amount of stretching that could be performed. Because previous research has indicated that acute static stretching can impair performance of the lower-body muscles, future studies are needed to determine if acute static stretching of the lower body has a significant impact on baseball pitching performance. It should be noted, though, that Knudson et al. (16) found static stretching of the legs along with the upper body did not significantly affect tennis serve velocity or accuracy.
No previous research has measured the effects of acute static stretching of the upper body on baseball pitching performance. Although most studies have focused on muscles of the lower body, only one study (16) used an overhand throwing motion (a tennis serve) to measure performance after static stretching. A short duration of static stretching may be performed during a warm-up because this does not appear to significantly affect throwing performance. A rest period of at least 5 minutes may help eliminate any possible negative effects of acute static stretching. The results of the present study, which are supported by previous research (16,35), suggest that acute static stretching of the upper body does not significantly affect pitching performance of collegiate baseball players.
Six 30-second static stretches of the throwing shoulder performed after an active warm-up had no significant effects on baseball pitching velocity or accuracy. A relatively short duration of upper-body static stretching followed by a rest period of at least 5 minutes may be included in a warm-up before a throwing activity without fear of decreasing velocity or accuracy. This study also indicates that acute static stretching of the upper body does not improve velocity or accuracy. If warm-up time is limited, abstaining from static stretching should not be detrimental to pitching performance. An active warm-up that includes at least 10-15 minutes of throwing appears to be an adequate amount of preparation for a collegiate baseball pitcher.
Thanks to coach Chris Schwarz and the UW-L baseball team for their cooperation and participation in this study and to Hannah Gaveske and Laura Capp for assisting with the stretching protocol. The results of the present study do not constitute endorsement of the JUGS cordless radar gun by the authors or the National Strength and Conditioning Association.
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