Training for a faster pace

Question
Greetings from a fellow expert (Microsoft Excel area)!

I'm a recreational runner and I enjoy doing a several 5K competative runs a year.  

I run 5K on a treadmill at least once a week (usually twice).  I also try to run 5K outdoors over various terrain about once or twice a month (I use a Garmin GPS watch to track my distance, pace, and heartrate).

On a treadmill I can run a speed between 8.5 and 9.0 MPH and a 5K in about 21:00 to 22:00 minutes.

Lately, during the summer temperatures between 90 and 100, my outdoor 5K has been about 23:00 to 24:00 minutes.  I attribute that to the heat.

Anyway, I've been stuck at this level for about a year...and I've decided I would like to push below 20 minutes (mainly, if possible, for a 5K coming up in a cooler October - I always seem to place 4th because the other 3 guys in my age group always run between 19:00 and 21:00).  

I'm usually not competitive on my runs...but by gosh...I'd like to win a token medal for a change ;).

What are your suggestions?
1) Should I work more weights on my legs (currently I do very little weight training on my legs).
2) Should I run splits (which I've never done).
3) Should I run shorter distances at a higher speed (I can run 1 mile in less than 6 minutes if I put my mind to it - and then I'm pretty much spent).

Thanks for any advice you can provide!  I know there are lots of websites that provide generic answers, but I'd like to get a personalized one for a change - I really appreciate it!

Answer
To quickly answer some of your questions, as you laid them out 1, 2, 3.

1: I don't think the solution is more work for the legs, as the legs get PLENTY of stress from fast running.  Rather, focus on total body training, such as breaking it down into 5 main actions: squat, lunge, push, pull, bend, & twist.  Squat/Lunge for lower body, Push/Pull for upper body, Bend/Twist for midsection.  Choose one exercise for each action & stick with that for a while.  I go through this in my free e-guide, The Mini-Max Method, found on my site, http://speeddialcoach.com

2. Splits are okay, but don't do them everyday.  1-2 times a week is plenty.  I like splitting up a workout into 400 & 800m distances.

3. This one ties into #2: try doing quarters (400m) in your race pace, or since you use your Garmin GPS, set the readout to kilometer readouts, and go by a min/km pace reading.  For a 20:00 5K, you'd need to stay at a 4:00/km pace or better.  I noticed with using GPS data in the kilometer format, training for a 5K became much easier, because you're not doing any more converting/conversions of miles to metric stuff all the darn time.  If you race in meters, train by meters, and keep the training simpler.  I've noticed my GPS training e-book, Endure!, has sold in many other countries because they go by kilometers instead of miles in their training logs.  I think that is half of our country's problem: we train by miles for a kilometer-measured race.  We get too focused on measuring our progress in miles when we should be measuring/training by our metric measurements we are tested at.

I hope this helps you out a little, feel free to ask more questions as you wish.

Rick Karboviak