I have a friend who irks me by introducing me as "old school." I'm always looking for something new, though it tends to make me vacillate between different training ideas.
The Edinburgh protocol
Actually, it might be Glasgow or Aberdeen - I should look it up. Though it's gone by several names, doing sprints to improve distance running has been around forever and it's had a variety of reasons behind it. James, then Canova, then Hudson, had people doing short hill sprints, which is almost entirely dependent upon creatine phosphate and is useful for sprinters, but I was never sure of it for distance runners. Then there was Tabata and 8x20 sec.(10 sec. recovery) all-out, which pushes from creatine all the way through lactate tolerance, but always caused me injury. Researchers in Scotland got it down to 3x20 sec. all-out, which hits the upper end of lactate tolerance and found that doing it 3 times per week for 12 weeks improved maximal oxygen uptake. That I can do. It's too early to tell if it's helping me any.
The late-Foster/Furman/Hanson bros. world
Supposedly, I've reached that point in my running career where high volume is not going to help much any more. It's possible to get by on three days of running per week, supplemented by cross-training, running very hard twice per week. Jack Foster ran a 2:20 marathon at age 50 that way (though he ran 2:11 at age 40 on higher mileage). Recent plans have been advocated of running fewer days and, looking at what is essential to marathoning and to what I don't do well, the follwing looks like a plan:
Tuesday: two hours, with 3x1.5 to 2 miles @ 1/2 marathon (threshold) pace
Thursday: two hours of hills
Saturday: 2.5-3 hours, with the last 4-8 at marathon pace
Sunday: two hours speed hiking/fast walking
That whole low carb thing
Though it doesn't appeal to me, I'm willing to put anything to the test - assuming it makes sense. Getting 45-65% of one's calories from carbohydrates is considered normal. 40% is where Zone, then paleo went; that's possible if one's careful. Then things went weird and people were advocating exceptionally low carb diets - and some were having running success with them. I kept looking at what they were eating and it made me ill, but still, I considered it.
Most people don't get enough vitamins D, E and folate, or enough zinc or calcium. These low carb diets could get those nutrients in sufficient quantity, so I started looking at it again. There is evidence for a healthy diet containing: 4 oz fatty fish, 2 oz. baking chocolate, 5 oz. red wine, 2 cups green vegetables (especially leafy greens and cruciferous), 1/2 tsp (3 cloves) garlic... not many carbs there!
Unfortunately, weird diets lead to weird deficiencies and I suddenly had to think about thiamin, of all things. If you eat grains or legumes, you get enough thiamin, but these have too many carbs. The alternatives: yeast extract (which is industrial waste, and most vitamin pills are derived from this same sludge) which tastes horrible to me, pork loin or sirloin or tenderloin in too large quantities, kidneys (which I refuse to eat) and supplements.
I've looked over what people are eating on low-carb diets and it's either nutritionally deficient, revolting in taste or just a bunch of potions and pills. Until I can find a way to test this that I can live with, this remains a thought experiment.