Again a good question to my website (http://www.bobbymcgee.com/) on the run/walk method for running & triathlon success.
"Hi Bobby, I'm a Level 1 Coach and recently watched your webinar 'Run/Walk Your Way To Faster Racing Times' (. I am very interested in the program and am thinking I will try it. I'm training for a 70.3 in June. I had a question - when you follow this program, do you suggest that every training run should be a run/walk? I run 3x/week. And, would that change if I ran 5x/week instead or 3x? In your webinar you suggest that someone may decide during a race to run the last 5K of a long run. If that's the case, wouldn't it be good to have some of your training runs be pure runs (no run/walk). Thanks!"
Thanks for your interest & query. If you only run 3 times per week, I believe, especially if you intend to race run/walk, which I highly recommend, that if you run walk EVERY session, you will be able to run at least one extra run per week, which will positively impact your run ability. However as a direct answer to your question I usually recommend that all runs over 45min should be walk run. Many, many age groupers would be best served running shorter, but more frequent runs & run/walking ALL of them. The pros I work with only do this on their long runs. If you ran similar volumes, but ran 5 times per week, you should see an incremental increase in your run fitness.
I understand your question regarding finishing the last 5km in a race without a walk break, but this is if you realize you are home free & could get home faster if you ran the whole way & even if you had miscalculated, at this late stage there is no harm done & you can simply take a walk break to restore yourself (reset) & then run on. If training, as you are, for a longer race it is not a bad idea to walk/run the majority of your run & then try to run the last 3-4 miles without walk breaks. This will increase your functional strength, but will increase recovery time & there is a greater risk of injury. A better bet is to simply pick up the walk/run pace in over the last few miles/km in some long runs – in this way you improve your specific fitness, teach your legs to be able to finish strongly & the risks of injury & delayed recovery are minimized.
Good luck & best wishes for a great race!