As I progress through the year I have noticed a change in my limitations. For example, early in the year during our weeknight hammerfest my heart rate would max and I would become very short of breath. This would lead to getting dropped. Now I can hang longer and have better times. On the ride (and during a race) my breathing remains comfortable and HR manageable, but my legs just become fatigued and/or don't have the strength to either hang with the fast group or continue after bridging a gap. This drives me crazy because I feel comfortable otherwise. What is the best way to improve in this area?
It's highly unlikely you are strength limited, however you are most likely power limited - sustainable aerobic power limited.
Without knowing much about you, it's hard to be specific about what you specifically should do, but in general it involves riding more (e.g. 15 minutes extra per week for a few months) and most importantly, including quality efforts in your training diet, especially those that focus on improving your sustainable aerobic power, and anything else specific to your ride/race demands.
That is achieved with a balance of ride time at various intensities, but especially with regular hard, sustained and sometimes repeated efforts from 5 to 90-minutes duration in and around your threshold power level (i.e. +/- 15% of threshold), or the effort level you could maximally sustain for about 40-60 minutes. Do a solid session once or twice per week, and combine with general quality aerobic work on the other 3-5 days.
Gaining an understanding of intensity of effort really helps.
That will have a far greater impact than any gym work will.
Good application of the fundamental principles of:
- Clear goals (know why you are doing the training)
- Sustainable progressive overload (with load being a function of duration and intensity, as well as frequency of training)
- Specificity (consider and replicate the specific demands where possible, not just physical but technical, tactical and psychological as well)
- Recovery as required
will take you a long way in this sport.