Matchstick Man - thanks for comments; good to see it is possible to progress to a sub 1.30 half on 3 runs a week; I run 3 times a week (one interval/speed mostly 4-5 miles, one threshold/tempo mostly 4-6 miles, one longer weekend usually 8-12 but also 14-22 miles when training/peaking for marathon) but on the whole haven't been doing as many miles as you; I will try and up my weekend run so it is more regularly 2hrs (13-14 miles - a bit slower than you?) or more, and I will also increase my mid week tempo/threshold run to more like 8 miles (do you think at target HM 1.40 pace?) to hopefully increase my LT? When I do my mid week tempo, i usually run at my 10k pace or a bit slower (45-50 min pace; my recent pb is 45.12); for my longish runs (10-12), I usually run at 9-9.30 min mile pace - slower than HM pace so too slow i guess?
Claire - for a half marathon, not sure what others might suggest, but i shouldn't worry overly about gels/drinks etc - they are far more important for a marathon when runners very often run out of glycogen (carbs) at 16-20 miles; for general half marathon prep, i would eat more carbs in the last few days (so at least you know you are starting off with good carb reserves - though a normal diet would probably be ok to be honest), and also be well hydrated and get plenty of rest/sleep; on race day, eating a good high-carb breakfast 2-3 hrs before is a good idea (eg. cereal, toast etc - so at least you have replenished your liver glycogen which gets depleted somewhat when you are sleeping) (though don't worry too much if you can't eat a big breakfast - i have a friend who can't and she is always fine on 13 miles+ runs!); if you like energy drinks, perhaps drink a 500ml one in the morning too (but leave time to go to the loo) (not essential though - water equally ok); during the run, drink at least half litre fluid, more like a litre - doesnt really matter if it is water or energy drink, though again it would not hurt to drink a 500ml energy drink and up to 500ml of water - up to you. As regards other carb foods (gels, blocks, jelly babies etc), i dont think you need them on a 13.1 mile run - but they wont do you any harm! Good luck! (don't do what i did and run too past in earlier part of race!)
from what i have read, muscle soreness after exercise is likely to be due to micro muscle tears - normal and should get less of a problem the more you train
lactic acid / lactate - usually is flushed out quite quickly (ie minutes)
lactate threshold is point at which your system cannot get rid of lactic acid quick enough, the result of which is fatigue - this can be dramatic (eg. complete jelly legs, dizzy, fainting, sick etc) if you have been running above your threshold for a fair amount of time
increasing lactate threshold (by various training regimes) is a good idea if you want to run more efficiently and faster for longer
i agree with the lactic acid / lactate build up view - did a flat, cold half in Feb and at mile 9 my legs went completely, dizzy, felt sick - had to walk; i had done loads of training, wasn't ill, had lots sleep, and diet was good (carb loaded etc) so cannot have been lack of glycogen (i have done alot of 8-12 mile runs and never took gels etc and never had a problem except for this race); all i can think of is that i was trying to maintain too fast a pace for me (my previous PB was 1.47 and i was running at 1.39-1.42 pace for the first 9 miles)
solution i think is to reduce pace (especially early on) or increase lactate threshold, or both