Old n' Lazy said:
I just got back into cycling again this spring. I have been training about 8-9 hrs per week (for about 6 weeks) with one long 4 hr ride and two shorter 2-2.5 hr rides. THe 4 hr ride is at about 135bpm and the other two are around the same but with 30 minutes of intervals (40 sec "on" 20sec "off") or 20-25minutes of hard effort (165-170bpm). The last MTB race I showed up at was awful! I had no lungs, my legs felt fine but I was ragged breathing so bad I could hardly see. I was well rested entering the race. What needs to change in my training to get me competetive?
First you need to build core aerobic fitness and when that comes up a bit you need to top it off with some high end work, especially for mountain bike racing. Based on this:
The last MTB race I showed up at was awful! I had no lungs, my legs felt fine but I was ragged breathing so bad I could hardly see.
its clear that you were totally anaerobic during your race. Thats a clear indication that you need to either back off your race pace to something you can handle or build your aerobic fitness high enough to match your goals.
I take it your 135 bpm 4 hour ride is fairly comfortable(HR is only useful relative to your own fitness and your own heart but relative to the 165-170 bpm hard rides it sounds pretty comfortable). That sounds an awful lot like old school Long Slow Distance(LSD) training. That can work for some but usually takes a lot more training hours per week to see much improvement from LSD work.
I trained with an LSD base topped off with specific work for many years with inconsistent and overall fairly mediocre results. For the past year or so my core aerobic training is based on Sweet Spot (SST) work along with some longer Tempo(a bit easier but still more effort than traditional LSD) and Threshold(focused time trial pace efforts for 10 to 30 minutes) work. I train about half the hours I used to and my results are better and much more consistent.
The key is to work in the appropriate training levels for long enough durations to target specific energy delivery systems. If you want to improve your core aerobic fitness you need to do efforts(SST, Threshold, or Tempo) that are both steady enough and long enough to encourage adaptations to your aerobic energy delivery systems. LSD training based on fairly comfortable long rides will get you used to being in the saddle and can help train your muscles to store glycogen but they are relatively low stress and it takes an awful lot of that sort of training to see much improvement for a racer(they can be great for a recreational cyclist just getting into cycling but it sounds like you are beyond that point).
Your microintervals can work if the overall average stress (power would be a much better measurement than HR for this) places you in the appropriate training level(Tempo, SST, Threshold) for at least 10 minutes at a stretch and preferably longer. If the average stress(power) is too low and the peak stress is higher than those levels then you are really training anaerobic fitness, not your core aerobic engine. That can be great in the final stages of race preparation and really useful for those times where you really have to dig on a steep single track but it trains the wrong system for steady state speed and power or the ability to hold pace on a long climb.
You should search these forums for discussions about SST, Theshold and FTP and read these threads:
http://www.cyclingforums.com/t397725.html
http://www.cyclingforums.com/t314849.html
They are pretty inspiring and although they focus on road fitness the basic aerobic fitness is the same. As an off road rider you will want to work other systems as your fitness improves but there is no sense doing anaerobic work until you get your aerobic fitness up a bit.
I would recommend going from 3 days to 4 or 5 but cutting the durations so the weekly hours work out the same while bumping up the intensity of the long ride(cut to say 2.5-3 hours) and changing the shorter rides to long interval sessions like 2x20 at SST or 2x45 at Tempo(in 1.5 to 2 hour rides). Combine that with some good rest days and decent nutrition and you should see improvement.
Good luck,
Dave
edit-looks like our posts crossed in cyberspace, but yeah +1 on Wiredued's advice.