This post is itself a bit of a stretch, as I am continuously injured and there are at least a dozen people who regularly read this blog who deal with injuries as part of their profession and know a lot more than I do.
There's a bit of controversy about stretching for runners. Some runners never stretch, do quite well and think stretching is a waste of time. "You never see racehorses stretch!" is my favorite comment along this line. (I like to point out that racehorses also retire when they're 4. I was pretty limber at that age, too.) The truth of the matter is: some runners don't need to stretch. If you never get injured, you don't need to do a stretching routine. There's actually a correlation between stretching and injury that sparks the controversy: runners who stretch are MORE likely to get injured! There are two reasons for this (and here's yet another colon): 1) Runners who get injured take up stretching as a method of preventing another injury, so the cause/effect relationship is backward and 2) Stretching an injured muscle makes things worse.
Incorrect stretching also leads to injury. Jerking motions, trying to push a stretch, can lead to injury. "Overstretching," or doing too many stretches too long can also lead to problems; it is typical of athletes to want to progress to advanced stretches once they can manage easier ones, but one really isn't training to be a contortionist. Hyperfexibility can be a problem - as a child, I had hypermobile joints ("double-jointedness") and could flex my knees backward about 10 degrees (I can still contort joints in my arms and hands); I suffered from knee injuries until running had developed the surrounding musculature enough to stabilize the joints.
And now I have problems with overly tight hamstrings. [Sigh.]
I'm forever stating that the best way for runners to train is to run. The best way to deal with weak ankles that are continuously sprained is to run on uneven terrain; if you can't run on trails, then you have to resort to stretching and strengthening exercises. The best way to develop leg strength is to run hills; resistance training is a distant second choice. The best way to keep joint mobility is to do sprints; stretching is a second-best alternative.
Time to cover the basic causes of injuries. First, there's bad shoes: I won't cover black toenails, bunions, corns, calluses, blisters, hammer toes, etc. Second, there's bad technique: beginning runners usually develop shin splints, which go away once they learn (usually unconsciously) to run using a pawing motion of the feet, rather than holding the ankle in one position. Then there's accidents, which can lead to serious injuries of ligaments and bones and which require treatment too specific to go into here.
Then there's the two most common causes: overuse and doing something new; the two go together. Running slowly causes one's muscles to adapt by shortening to make the repeated motions more efficient. If you do all your training at a slow pace and then try to race, you force your joints through a greater range of motion than usual and muscle tears then become more likely. That's why I stress running fast on a regular basis.
One of the more common reasons for trail runners to get injured is the near-fall (here come's another colon): stumbling over a tree root or rock causes one to make eccentric motions to retain balance - some rather comical! - and these motions force small muscles to work extremely hard for a second. It's not unusual for a trail runner to have sore muscles the next day in unexpected places (I once pulled a triceps while running). Muscles of the torso (I hate "core") become important for balance and control.
Lastly, there's structural problems. The most common is a leg length discrepancy; more people have one leg at least an eighth of an inch longer than the other than have legs exactly the same length. People who have no structural problems run fluidly, gracefully, and they rarely, if ever, get injured; these are the people who don't need to stretch. You may not know what you look like when you run, but you can tell your running friends apart by their running styles; chances are your style isn't perfect - nor should it be! One's body adapts to structural irregularities by changing running style from "perfect." The downside is that it makes injuries more probable.
The basics of a stretching routine
I'm not going to give a list of exercises to do. I do about 35-40 different ones and not as consistently as I should. There are plenty of resources that will help in finding stretches to do; look for ones that are considered useful in dealing with the most common runner's injuries: achilles tendonitis; "runner's knee," iliotibial band syndrome, plantar fasciitis, ankle sprain, calf strain, hamstring strain, groin strain and lower back pain (sciatica, piriformis strain, hip flexor strain). Come up with a routine and do the same exercises in the same order so you remember them all; cover all the bases. If a stretch doesn't seem to do anything, don't abandon it or try to find something more challenging, just don't spend much time on it and move on to the next one; I am always surprised when an exercise suddenly seems difficult and that is precisely the sign that one needs to be wary of an injury beginning.
I suggest the following as a very minimal catch-all (wait for it...another colon): before going to sleep at night, move each joint through its full range of motion, starting with the toes and working up to the back. It's at this time of day that one is most flexible, so one is least likely to hurt oneself by stretching. Also, this flexing and relaxing of muscles is calming and helps prepare one for sleep.
[And I promise to stop obsessing about my overuse of colons!]
6 hours ago