Longest weekly run / total weekly mileage percentage

Depends on what your goals and fitness are.

Most place it somewhere between 25% and 50%.

I've found around 30-40% to work nicely.  50% seems way too high to me, unless you are training for a marathon using a beginner program with lower mileage. 

From my experience, total volume is a better goal rather than long run distance.

If you are just running or focused on running, I like to keep it under 30%; not always possible but that is what I shoot for.

Shane

x2

I just posted a very similar question here:

http://www.beginnertriathlete.com/discussion/forums/thread-view.asp?tid=128100&posts=10&start=1

When approaching my long runs for a marathon build (18-20mi), I'd like to be in the 35-40% of weekly miles (~50mpw).  I think this should be fine for a period of time (6-10 weeks) prior to the marathon taper.  I also get into high % of total mileage when in my HIM build (3 runs per week, including a 12-14mi weekly long runs put me in the 40-45% range).

Consulting with several running coaches, doing long runs 35%+ of your weekly mileage throughout the year is a recipe for injury.  I believe limiting this practice to specific phases of your program can be done with caution.  Also consider total training load (volume and intensity of running) and how your body is adjusting.

Happy training!

I'll chip in... and skew the results. 

I usually wind up around 50%... sometimes as high as 80%.

Are you also biking or doing other workouts, or is running your main or only form of working out during this period.  I think that could make a difference.

But yeah, 30-40% is pretty normal, though 50% or even a little higher isn't crazy.  Depends on where you're at and what you are hoping to achieve.

As a general rule, the higher your total volume, the lower percentage of it will be your long run.  (I guess this is probably obvious.)  At least, that's the way it generally goes for straight marathon training.  I'm not sure how adding swim and bike into the mix changes things.  I'd be curious to hear from experience triathletes on that point.

You don't count.