What was the workout? If you're doing base, I wouldn't expect your heart rate to ever get much out of the aerobic range. Stick with it and see what happens when you finish this block and redo your ftp test. Usually it takes a couple to get those right as well

It was Goddard. I guess you’re right, I’m just used to chugging away at 150-160bpm for hours on end during the winter! Averaging 129 just feels too easy! It’s only a 6 week plan so I guess I’ll see what improvements I’ve made in 4 and a half weeks!

It is entirely possible your ftp is set too low, that's an issue I've had a lot of friends new to the whole power testing thing tell me they had.
Also, lookong at that workout i wouldn't be surprised to see a low average hr, just from How much of it is easy riding

I've had the same issue, with some of the sessions leaving me feeling like I didn't do much. I posted this exact query on the Trainer Road thread and Nick told me it could be due to my inexperience with FTP testing as well as the general inaccuracy of HR training.

I've done 3 FTP tests this year, going from ~240ish to 279 (as of 2 weeks ago). I suspect most of these gains are from testing better as well as fitness. Since the most recent ones, I'm noticing my HR is more in line with what I'd expect from the base workout sessions.

That’s interesting to know, my power is really low, recent FTP test showed 173, I put it to 190 and that felt fine for recent workout. How often did you repeat the test? I’m 67kg so light but still a low watts/kg, this is the problem, I have no idea what my power was even when I was fit! I can hold around 19mph for an hour with about 1500m climbing but that’s all I know at the moment! Wasn’t too worried about the number, more just looking for a training aid. How often did you recheck your ftp?

I believe they recommend retesting at the beginning of the next training block. The 3 I've done this year have been prior to starting a new training plan on TR. I've 2 weeks into the Middle Distance base plan and so will need to retest in 6 weeks when it comes to starting the build phase

There's no point following a plan, just to follow a plan.
If the current plan is based on %FTP and you think your FTP is very inaccurate, I'd shelf the plan until I had that figured out. If you know how you typically perform based on HR then maybe use that for pacing initially and do some 2x20min sessions to get a feel for what sort of pace you can sustain on the trainer. If the power figure you sustain for 2x20min intervals is close to or above your tested "FTP" without you being severely uncomfortable then your FTP value is almost certainly not correct and needs to be increased. It's not a wasted session. A hard 2x20 is never a waste of time ;)
Regardless, the values you get from your 2x20 will be a useful starting point when you do the FTP test again. Aim a little harder than you managed to sustain for hard 2x20 intervals and see how you get on.

There is a middle ground between long steady sessions and a prescribed plan. There's no reason you can't put together your own plan to fit your preferences and needs. From my experience on the trainer, threashold and VO2max intervals, maybe mixed in with some races on Zwift are far more productive, and more satisfying, than spinning while watching a film (which I find very hard to do with any decent power output).

Having had a look at Goddard, it's probably not the best workout to be looking at average HR; it's intervals of one form or another pretty much from start to finish! From the description it looks as though that workout is primarily designed to focus on form rather than stimulating physiological adaptation, so (1) it may not been the most taxing and (2) the usefulness of average HR in a workout like that is pretty much nil. I'd carry on with the plan and see how things progress, or switch to a plan that has more of the kind of workouts that you want to do.

Having said that, I'd say retest as soon as you can fit it in e.g. after your next rest day, when you're reasonably fresh. Use your adjusted FTP value as a new target, so 190W divided by 95% = 200W target power for the 20-min test interval. There's definitely an art to FTP testing, that 20 min interval should damn-near kill you, so if you reach halfway and still feeling good, push it on.

Note that for some completely inexplicable reason, the TrainerRoad "20 min FTP Test" workout has the intensity of the test interval set way too low (something like 102% of current FTP), so if you use this to pace your effort you'll come up short of your current FTP value. I've asked them why this is and they never gave me a good explanation, they just stated that they wanted to change the whole way that testing is done, which incidentally was over a year ago and still nothing has changed.

the test interval is just a guideline. only use it really for the warm up phase of it and for the 20 minute test, go balls out. seems like you may be like me and feel like you need to have that be accurate, then add intensity to it. but if you're going 102%, your FTP will actually drop some.

I've done TrainerRoad plans for the past 3 winters. Of course you could just test again but, if you want to wing it, here is my unscientific personal thoughts on guessing at your FTP while doing a TR plan. When I felt my FTP was accurate, the easy workouts were easy and the hard workouts were hard but I could make them. It was not like any particular workout was devastatingly hard but I was really glad when the rest weeks came. I don't have too much experience with setting my FTP low because I generally lie to myself, but the times I felt my FTP was set too high, it showed up later in a block when I started having to bailing out on intervals or even taking an unscheduled day off before I got to the schedule rest week. My view would be that if you are not getting progressively more fatigued as the weeks go on, your FTP is probably too low.

Goddard's IF tends a little high because of those 130% efforts. While those 30" repeats eventually catch up with you, they're not that hard. I'd be interesting in how your HR reacted during the last two intervals in sweet spot. That's the tough part of this workout.

FWIW - looking at Goddard, that is a great workout but it is not a workout that would drive your HR up to a high steady level. It has some short hard efforts but you are supposed to be doing single leg drills for a decent portion of the workout . . . . That alone should tell you that HR is not the focus. Last time i did that workout my average HR was only 126. But IF was .76 and I had a decent NP and got some great form work in with the one legged drills. And, looking back on where Goddard fell in my base plan last year, it was number 4 of 5 on the effort/TSS level for that week's workouts and I turned in my lowest average HR for the week.

The key thing to remember about a training plan is that not every workout is going to be the same either in effort or goals or your chosen performance metric (e.g. HR). Pay attention to the plan over time and don't sweat the individual workouts.

The whole way TR plans are structured are exactly to add in the variety you describe. So following a plan is as simple as following a plan.

PS. there is a TR mega-thread here: http://forum.slowtwitch.com/...trainerroad#p3560133
where you are better off asking you specific questions and getting answers from both the forum and TR themselves.