From my experience of doing year 12 PE at school only like one or maybe two replies are useful...
Firstly... Why choose downhill??! Your not going to get extra marks for choosing a harder sport.... Best off doing something like AFL, Rugby, Soccor, Netball or something along those lines, soooooo easy to get a good and thorough training program on paper..
Anywho... Firstly you need to figure out what energy systems are most dominant in Downhill... Obviously ATP-PC system will not be a dominant system except for the first 7-10sec of the sprint off the line.. The Lactic Acid system will be dominant for a majority of the time (like a 2-3min course) though the Aerobic system will also play huge role also with energy production..
As Downhill is not like a 100m sprinter, it is harder to focus on what area of energy systems to train as different tracks will alter percentages of what energy systems are dominatly used..
Overall though, you'll find that the Lactic Acid system and Aerobic system will both coincide as the most dominant systems on many Australian tracks (bar Thredbo and other long long tracks where aerobic will be the most dominant)..
I say both will be both dominant semi equally as in fast technical sections and pedally straights you'll be utilizing most of your ATP production from the Lactate system while in easy going sitting down parts of the track where your 'just taking it easy', the aerobic system will be providing the majority of the ATP to the working muscles, while also helping remove accumulated Lactate and Metobolites from the blood...
Okay... So keep in mind the energy system interplay and so forth...
Anywho... You need to analise the run and find out what muscles will be used through out the race, and which will be used the most..
Once you have figured out energy systems used throughout the run and what muscle(s) group(s) are used mostly you can start deciding on tests on which you will get your Downhiller that you will be designing the training regiem for...
You should have learnt that in order to induvidualise your training program to whoever you are designing it for, you have to test them on specific tests relevant to their sport (downhill)... Once you have chosen these specific tests, you can get the person to complete the tests while you record the results..
From these results you will be able to determine what areas need considerable work to bring the induvidual up to standard and which areas are already or above standard and dont need so much attention...
From these results you then can start building your program and induvidualise it to the downhiller as much as possible.. Not everyone will have the same training program suit them..
Now, what to include into the training program?? (also depends on whether it is pre / in or post season also....)
Certainly need a weights program incorporated while also including aerobic and anaerobic excerise and movements incorporated also that will be relevant to downhill... Consider Fartlek, Short / Long intereval, weights including power movements..
As you wouldnt give a program to a swimmer with heaps of running involved nor a runner with heaps of swimming... Same as you wouldnt say to a downhiller go do 600km of road riding each week... Needs to be specific!!!
(god i'm starting to get tired and missing heaps........)
Also remember as the designer of the program why you are including what you are and what the objective is and how it is relevant and specific to downhill...
Also take into account Lactate Inflexion Point (LIP, as this will help the downhiller compete at higher heart rates with out accumalting Lactate), VO2 Max (as the more oxygen the rider can inspire and expire will help with more glycogen being broken down for working muscles quicker while also aiding in removing Metabolites quicker and faster also), muscle movements also (inflexion / extension and so forth..), what energy systems are most dominant and when and why and so forth...
So much stuff you have to consider when trying to design an iduvidualised training program for someone...
This is really brief... i could go on for pages and pages but you get the idea..
This will only give you an idea of what you need to consider.. You still have to research a hell of alot..
I still advise you should switch to something easier which you'll be able to research a bit better..
Patto