I have been cycling for about 2.5 years. I train on a computrainer 80% of the time and have seen improvements. However, based on my swimming improvement and running improvement, it seems like I have hit a wall with cycling. I usually hang out around 175-185 watts for a longer effort (2-4 hours). I cannot fathom how people hold 300+ watts for this long.
Also, I cannot hit my heart rate targets before my legs give out....so if the workout calls for Z3 HR, I push as hard as I can so I can survive the distance...but my HR won't approach Z3 until the very end when I am grinding it out to the point of collapsing at the end of the workout.
From an RPE perspective....I am able to push past pain and push it to a 8-9 on a scale of 1-10 during these efforts. I feel like I am working very hard.