I always have a hard time hitting the prescribed target watts on longer sweet spot and threshold workouts. I am consistently about 10% below target.
(about a year into TR, hoping in time, I can hit all of the prescribed targets based on my ramp test results. I assume that the ramp test is over estimating my FTP right now, particularly for longer efforts, however, I am hoping in time if I can further develop all of my zones, I will be able to hit my targets as calculated from the ramp test? and my ftp will no longer be overestimating)
However, I did 2 outside workouts this week (Washington +2 and Mount Baldy +1, 5x7 minutes and 4x10 minutes respectively) which are the first 2 real workouts I have tried outside. I was climbing the same hill on both workouts and I found it manageable to be at the top end of the range for all intervals. My cadence was in the mid to higher 70’s.
I don’t think I could have been as compliant with the workout if I had done in on the trainer.
I did Galena this morning (3x20) my cadence was in the high 80’s to 90 rpm, and I knocked down the intensity to 90%.
I am curious if there is a relationship between cadence and output.
Also, how would the training adaptations be different if workouts done at a lower cadence but hitting the prescribed targets watts (vs higher cadence but lower watts).
I hope that makes sense.
Does anyone else find this for themselves?
The question is why? Higher cadences usually puts more aerobic strain on your body, lower are more anaerobic and put more strain on the muscles. If you like riding with lower cadences - do the workouts with 70s not 80-90s.
The Townsend Workout (90minute Adaption week) discusses the differences and benefits of high/low cadence, speed, force, power, aerobic vs anaerobic.
A cadence of 70 is low by any standard, a real grinding pace.
High power is associated more with say, track sprinters, ie, anaerobic power. But if you want to ride endurance distances, then there are real benefits of training your body to be more comfortable in the 85-95 range. As an example of the ability to change, all triathletes have little choice but to make that change, as ones running cadence is in that range.
Are you doing the indoor workouts in erg or resistance mode? If you are using erg mode, have you played around with different flywheel speed by truing small ring / big cogs vs big ring / small cogs?
Erg mode w/ small ring / big cog and the low flywheel speed might feel like climbing outside with the low inertia. High flywheel speed would feel more like high inertia riding on flat roads and be more difficult to keep the power up.
Re: cadence. I think it is worth experimenting with different cadences, but if upper 70s works for you, go for it. I know a regional, high-level triathlete and he averages 75 in most rides. I believe observations of high-level cyclists was that as their power output went up, so did cadence. Not saying I’m high-level, but I do find as my power output goes up I prefer a higher cadence due to the lower force required on each pedal stroke. I also find that erg mode really punishes me if I don’t keep the cadence up. Does your preferred cadence change between sweet spot / threshold / vo2?
A very ‘blunt’ way to look at it is that higher cadence gives the work to your lungs, lower cadence gives the work to your legs. As a coach I like all of my athletes to be efficient across a wide range of cadences (especially road racers). I have found in both myself (I am 47) and masters riders that I coach, that as the years go on the preferred cadence seems to start to drop. I expect that is due to a declining V02 as we age and a higher level of comfort with ‘sending’ the workload from the lungs to the legs (as I said at the start, a ‘blunt’ view, but I hope you get my point).
Lots of people find it easier to make more power outdoors, and lots of people find it easier to make more power while climbing, which typically means pedaling more slowly. I therefore don’t think what you have described is either unique or really worth paying much attention to.
You should, though, probably adjust your power targets based on the conditions (i.e., indoors vs. outdoors), just like you would dial back your expectations on a really hot, humid day.
You say you always fail to hit targets and that you suspect that your FTP is overestimated…well isn’t the answer right there? Knock your FTP down 5W and see how things change.
There’s something about long sweet spot intervals that causes me to fail if I let my cadence fall. So far to avoid the spiral of death, I switch from ERG mode to Resistance mode for later intervals (I usually do the first two with ERG on). And/or around the hour mark drop the intensity target for ERG. It makes me think my FTP is a tad high; then I do a higher intensity but shorter VO2 max/ anaerobic interval session and it seems relatively easy 
Do you set your ftp with the ramp test? Your vo2max power is likely higher than the 120% ftp that the TR algorithm assumes it is. If you’re good at vo2max, it probable overestimates your ftp, and underestimates your vo2max range. Drop your ftp for the sweetspot/threshold workouts, and add intensity to the short intervals.
I’ll need to update my FTP. At the moment I am going on my last 20min test back the 30th April and I have scaled that down to my current body weight. A ramp test I done a couple of weeks ago suggests it’s in the right ball park (the ramp test was 5w less than 0.95 x 20min (adjusted for weight)). Intervals.icu suggests in the last 42days its fallen to 4.91w/kg which is perfectly plausible given my current lack of training and stress.
My TR trial has run out and I’m taking a break sorting out a few things (hopefully they are 99% sorted) but when I resume I’ll try what you suggest. Good call 
Must be a bitch falling to 4.9W/kg…I feel your pain…
I think it’s each to their own with cadence. I often get concerned mine is too high. I average 105-110 in any interval of SST and above inside.
I’m more like 100 outside
I hope you don’t. Its due mostly to weight loss as the result of bowel cancer and chemo :-o
Massively ill conceived post, sorry, can never have expected that as a reply. Hope you’re back to where you were ASAP.
I try to keep my cadence in the 90ish range but once the power target gets to within 90% of FTP then I have to drop to low 80’s.
Pedal stroke is more efficient at lower RPM as well.
On my rollers i can use my gearing to give my cardio and muscular systems some alternating respite on harder workouts, is that how resistance mode works on a smart trainer?
I think we can train to maintain higher RPM but it does take time, I feel mine is improving slowly.
Also, power is power inside or out, Your FTP is no different so I would focus on hitting the power targets primarily at your chosen cadence.
Some sweet spot and threshold workout texts have different cadence work. Tallac +4 for me last week, had endurance spin ups, and low cadence work. Pretty sure Stromlo +4 or Picket Guard also had standing work.
Ultimately, if I have to grind out an interval, seated or standing, I will, as that’s what I’d do in the real world on a climb!