Since August 2017 I've been following a new training plan based on the 80:20 concept. I wanted to test it properly before commenting too much about here. To test it I targeted the St Neots half marathon which has a proven reputation for being a quick course. It's where I ran my two fastest half marathons with my PB of 1:41:58 being set 8 years ago. Since then I've run almost 40 half marathons but never really got close. Perhaps the best effort was spring 2017 during London marathon training when I really bust a gut to run 1:46 but it came at a cost, bringing back my achilles tendon problems. I also struggled hugely toward the end and had massively sore legs afterwards. However, on Sunday 19th November 2017, I smashed my 8 year old PB by over 3.5 minutes, setting a new best of 1:38:23
The difference is I've followed a science based approach to training using the 80:20 concept. Eighty percent of training is done at an easy intensity and the other 20% is hard. It reduces fatigue, reduces injury risk and gets you fitter and faster. The best bit was that I've also enjoyed my running much more than in recent years. I could go into detail but there's plenty of information on the subject. The concept is based around 'training effort' and the best measure of that is heart rate training. If your GPS watch provides HR data it helps enormously but you also require discipline to stick to prescribed work outs. If you don't follow the intensity closely, you'll not gain that much from it. What I found really works well is to download your workouts from a training plan, or program the prescribed workout using Garmin Connect. Then you let your Garmin watch monitor your heart rate to keep you in the correct zones and tell you when to change your effort. There are other ways to judge training effort but HR is easiest in my opinion.
I've no doubt you can find lots of 80:20 info and plans on the internet but I read a book by Matt Fitzgerald which provided a fascinating history to the evolution of the training concept plus the science which supports it
I also purchased one of his training plans from the trainingpeaks website from which I downloaded specific workouts to follow.
It works, end of, and I'm pretty sure it will work for anyone who STICKS to the plan, that means absolutely beasting yourself when the plan requires it during the hard interval sessions but running slowly the rest of the time. Give it a go for a training cycle.