I'm going to voice a dissenting opinion...

You don't need more work at LT threshold or above, you need more work on basic aerobic fitness. Here's how I think of it:

The amount of effort that you can put out for an extended amount of time is your aerobic base. You develop the aerobic base by lots of riding below your lactate threshold - quite a bit in fact. Carmichael's approach sets 85% (83% if you're older) of your 3-mile field test average, which is pretty low. I think Friel's approach will end up with a similar range through a different approach.

Think of a chart that shows your HR over time. If you draw a line across at that "endurance" HR, that's the rate that you could keep up for a long time (limited on food and water, mostly).

On top of that, you can do short bursts of effort. Think of those as little spikes in the graph that run for short periods, corresponding to hills, pulls at the front of a paceline, catching up on a break, etc. The methods listed by others in this post are good at developing that short-term power, dealing better with lactic acid, and recovering quickly from such efforts.

But they don't help improve your aerobic base.

The other people you're riding with probably have both a higher aerobic base and a better ability to deal with the extra power demands. On the hills, most of their power is coming from that base, *and* they are able to recover better. You are dying on the hills, and that's why it takes so long to recover. (just a note - some of the people you ride with may be dying as much as you are, but they have some time to recover before you get to the top)

My advice?

First, don't get discouraged. It takes a long time to build an aerobic base - months/years.

Second, I think you should temper your workouts. Group rides can be really intense and it's easy to work harder than you should. Try to ride the hills so they don't absolutely kill you even if the group has to wait, and that should leave you more energy to hold onto the paceline. And don't do them too much.

You can't really determine heart rates based on formulas. You want to base your ranges on where your lactate threshold is, but that differs based on your fitness. Not to mention the fact that different people have different sized hearts. I think that Friel's book has a way to set training ranges, and I know that "The ultimate ride" does. Look at that, and figure out what your endurance/base heart rate range is, and try to spend about 95% of your riding in that range. That will not only give you the best aerobic benefit, it will give you the most weight loss benefit.

Having said all that, without a test, I'd guess that your overall average should be in the 120s, and you shouldn't spend much time above about 140 - not more than about 5% of the ride time.

Some more information here on the Carmichael field test. I've found it to be pretty useful.

http://www.bikeforums.net/archive/in.../t-171587.html