I note you recommend the MAF method up until a point where you plateau. Then what...? then do you bring in some speed work...?

The short and sweet answer, which we typically give to the average enthusiast is: yes, train MAF until you plateau, or until you have been improving for 3-6 months. Then you add some speedwork.

Most people respond well when their volume of anaerobic training is 15-20% of their total training while 80% is at or under MAF. The basic idea is to make space for hard training but also to train slow to promote recovery, increase endurance (which also means "tolerance to greater training volume"), and to keep the body healthy.

In a more sophisticated sense, the real goal here isn't to blindly precede all anaerobic training with months of MAF, but rather to keep the body healthy. We usually recommend the former (months of MAF) because the percentage of athletes and enthusiasts who exist just before the point of breakdown is immense. So, in order to produce a training structure, the important thing is to keep a person healthy and developing endurance with a preponderance of aerobic training (80-85%) while figuring out how much anaerobic training they can tolerate without dramatically increasing their stress levels.

In certain cases, a polarized training strategy that I might use is:  challenge aerobically well-trained people with anaerobic training for 2 consecutive days, until the stress increases slightly (but staying well away from any damage), and then back off with up to a week (or more) of strictly aerobic-only MAF training. Allowing a complete recovery is the best way for the body to grow and learn from periods of high-intensity training.

We like polarized strategies at MAF, because they contrast training stimuli from each other. This allows the body to grow from each of them individually. If the intensities and durations of workouts blend too much with each other, the body gains less from any one of them, and gains less overall. In a nutshell, this is why after a long period of MAF training, people start to see fewer aerobic gains until they eventually plateau. That is the best time to consider implementing a polarized training plan with 80-85% aerobic and 15-20% anaerobic training.