1) If your legs are giving out before your heart/lungs, pedal a lower gear at a higher cadence...
2) But it sounds like the real thing to do is to build up your legs. I would do the intervals mentioned above, alternating hammering and recovery.
3) Also I would go into the weight room and work on the muscles...
4) The other thing you might try, and don't laugh at this, is going to a spin class at the gym...
5) The last thing I can think of is, are you using the whole stroke? ... do you also pull back, pull up, push forward?
... On long rides sometimes I do four strokes concentrating on pushing down, four pull back, four pulling up, four pushing forward, etc. People also do single-leg pedaling drills for this purpose too. Then, when I am trying to ride fast and the legs are starting to hurt and can't push down hard enough, I remember (sometimes) to switch on the rest of the stroke and it feels like a turbocharger. Okay, a little turbocharger.....
Wow! To respond to your interesting points:
- I get the relationship between higher RPM and speed. I have not worked on it enough, but I start to float around 110 unless there's a lot of resistance (e.g., pushing on a descent to get over 40 MPH). On my last top speed effort I was able to reach 116 RPM. Last year at the end of the season I managed to reach 120. But that's demanding on my body and mind.
- My speed intervals (I've done maybe 6 sets over the past two years) have been disappointing. 3 minutes "go" (21-23 MPH average) with 3 minute recovery. 4 or 5 repeats on a pretty flat course. I didn't notice any lasting effect. (I did, however, feel my hill intervals seemed to help.) The low speed at max effort was depressing.
- I think my legs have a lot of power. I belonged to a gym for my first year. To get in good-enough shape to cycle. My leg strength was very good (I'd set the pins at around 80-90% of the machine limit). Also I was very good cranking from the start in the racing clinic.
- I did do several spin classes when I belonged to the gym. It seemed like it might have helped some. I would have won every class if they measured success by the quantity of sweat produced. But alas, no gym now.
- Pedal stroke - No, I don't pull up (in the racing clinic I asked and everybody else said they did). It doesn't seem to help me much. I have never read/heard about breaking the stroke into back and forward. And I have rarely done single pedaling. There are too many riders promoting this idea. I think I should listen.
And, per your subsequent response, I did not mean to imply that cranking it up to 22 (my peak in that mile) was easy. You say roughly double the watts? That sounds about right to me!
So, I will work on my pedal stroke, give intervals a serious try, and consider re-joining the gym. Losing weight is the most important issue, but that falls into a different category in my head. My focus in this thread was what to do beyond losing weight.
Thank you all for your responses.