hey mate, the taper is in essence you reducing your training volume over the period before your race. Depending on your fitness levels, how hard you have been training, and the race itself... depends on the taper. During this period, you dont want to do NOTHING.... but you want to be fully recovered come race day. For a mountain marathon, I would recommend a taper of 1-2 weeks, the first being your usual routine, but with a decreased volume, them race week being a few short runs and strength sessions. Keep one of those runs as some kind of interval, to keep your muscles fiting, and expecting to have to work... and then for the day before, total rest, apart from walking. I would also recommend that for the week before your race you drop your protein by about 30g per day, and increase your carbohydrates by 30g+. First few days of the week a low GI carb (like potato) and then as you get closer, switch to high GI carbs, like race cakes. We want that body flooded with carbohydrates. Also include some of those BEET IT Shots (1 a day all week, then 2 a day for the last 2-3 days), as the nitrates act as a lactate buffer and helps you work harder for longer in the race.