I've been hearing lots of contradictory message about stretching in relation to sports.
Some says that it's no use to stretch muscle before practicing physical activities while others always do it.
I do understand the benefits for after-effort stretching as a mean to alleviate muscle pain or cramps. I'm a regular runner and baseball player, should I encourage myself to stretch before practice?
There are three main types of stretching that the general layman will be familiar with. There are a couple of others, but they are extreme techniques, and generally not used by the everyday athlete.
Ballistic is old fashioned, and has been contraindicated for quite a while. One of the big risks is activating the stretch reflex in the tendon (This is what causes your knee to jerk when the doctor whacks you with the hammer), and this causes your muscle to try and tighten (shorten) at the same time you are actively lengthening it. This can produce tears, avulsions or tendon ruptures.
Dynamic is recommended before activity, especially if you are doing an activity that requires great extremes of motion (Such as martial arts or gymnastics). This is simply doing the motions of the sport starting with slow, short movements and gradually increasing the range and power. Skips into bounds before running is one example of this. As evidenced by this study, dynamic stretching before activity showed greater gains in jump power, where ballistic and static stretching did not show the same gains.
Static should be done after activity if it is done. Several studies have shown that static stretching before activity (especially in power based activities) actually decreases performance. The main purpose of static stretching is to increase range of motion (ROM) in the area being stretched. This study shows a decreased resistance to passive resistive torque (How far the joint can move before resistance begins), i.e. gains in flexibility with static where ballistic did not show the improvement. Ballistic did, however, reduce stiffness in the studied tendon (Achilles).
There is currently no evidence that stretching will alleviate muscle pain, and while it is popular to do, not much evidence that it helps alleviate cramps, either. Static stretching (contrary to popular belief) has also not been proven to reduce injury rates (As shown by this review article of the literature) or assist with such things as delayed onset muscle soreness (DOMS), "flush" lactate out of the muscles, or anything. If it helps relax you, or if you need extreme ranges of motion for a specific sport, it can help, but other than that, there isn't much evidence for it to support performance increases.
Also, since you mention that you play baseball, there is some evidence (Although I can't find the study at the moment) that preswing warmups should be done with a lightweight bat rather than a weighted bat, as it helps increase the following swing speeds.
Addition: While reading through references, I did find some notations that ballistic stretching post exercise could possibly produce greater gains in flexibility, at the cost of a higher injury risk.
Here is my answer from yesterday on Biology.SE. There is probably some overlap but I have linked articles with data available with my answer that may be of interest. As a note, the question on Bio was about warm showering to prepare for a sporting event. I am leaving the post as is since the information is still relevant and useful.
I am going to address only the stretching portion of the question since some misinformation is out there. When you say stretching, I hope you mean dynamic as opposed to static stretching especially if you are about to compete in a sport. If you are referring to static stretching, taking a shower may be a better option then, but if you mean dynamic stretching, a shower will not provide a greater benefit.
For peak performance, athletes or weekend warriors should use dynamic stretching prior to an event.
In previous research it has been recommended to use dynamic stretching as the primary method of stretching pre-event warm-up before high speed, and power activities (Little & Williams, 2004). The findings of this study agree with that recommendation for agility activities as well. This study supported the use of dynamic stretching in eliciting the greatest performance in agility movements by decreased T-Drill time. The findings of the current study are consistent with those of Fletcher and Jones (2004), and Young and Behm (2003) who determined that dynamic stretching elicits the best performance in power and high-speed activities [1].
However, static stretching does not improve performance and can actually lead to injury.
The current study found static stretching to have a negative effect on agility, and acceleration (Fletcher & Jones, 2004; Nelson et al., 2005). As acceleration is a component of agility, these findings support those of Fletcher and Jones (2004) and Nelson et al. (2005). Agility also involves components of braking, and change of direction. Static stretching prior to agility activities was found to have a negative effect on agility performance [1].
To read up on dynamic and static stretching as well as other types of stretching, I would recommend MIT's Types of Stretching page.
Additionally, the references to my reference one provides many more useful articles to look into.
Although stretching is not the only answer, you should certainly do some pre-exercising. In a state of inaction, your muscles contract and tighten, and also lose heat. This makes them brittle and inert. Going straight into heavy exercise can cause significant damage, and so in going from inactive to fully active, you should ideally 'warm-up' with a more moderate set of exercises. This can include stretching, and should address all the muscle groups your main activity uses.
Here are some references that agree with me:
With running you can combine the warm-up into the run by starting off by almost walking.
