If you're a runner following any type of training program you most likely have strength training (ST) days built into your weekly routine. At some point you may begin to wonder how much is enough, or too much, or even if/when you should cut ST out of the program as you get closer to your big race. Let us begin…
First, the principles of Periodization (the guiding hallmark of most training programs) state that the ST volume can be high when you have several months until your peak race, and that you should generally reduce the ST volume in the preceding weeks of your big event (you can use the term "taper" here, though I don't personally use that word in coaching). So, if we use the Marine Corps Marathon as an example (late Oct), you would pile on the ST and cross-training (XT) in the winter and spring, slightly reduce the volume and intensity of ST and XT in the summer as you increase your run volume/intensity, and then around Oct 1st you would consider drastically reducing your ST workouts so that you are better rested for your key run workouts. That's the short answer, and a general answer that applies to most non-elite runners (myself included).
One special consideration is whether you have a muscular weakness or imbalance that you're trying to correct through ST or physical therapy. If so, it's best to follow the therapist's recommendations. In that case, you may need to follow through with the ST closer to race day, although certainly nothing too intense at that point.
Another major consideration is your schedule: How much time in the day/week do you have for training/exercise? If push comes to shove, then 90% of the time you're better off doing a run workout versus ST. This is one of the main services of DC Running Coach, the time management and mental approach to training. Ideally, you could do as many ST workouts in the week that your schedule and body can handle, but when things pop up that disrupt your weekly routine then always keep running the priority.
Finally, if you're running a fall marathon you can keep working hard in ST and XT (though ST should get more priority than other XT) until about 4 weeks out. Keep the ST run-specific. A good personal trainer or coach should be able to show you what the run-specific strengthening exercises are, as well as how many sets/reps to do for these functional exercises. If you're into Crossfit and group ST classes, consider pushing them aside in the summer/fall in lieu of more run-specific training. Get back to the non-specific ST after you've recovered from the marathon. This is another principle of Periodization, specificity of training.
This blog could go on an on, as I'm a staunch supporter of ST for all runners! If you have questions/comments, drop me a line and we can chat about your goals and training.
Here is a related blog about core training, Pilates and yoga and another blog about off-season training.