I was afraid of that. I have been careful to avoid saying that slope mode is bad. For me, a slope specification in my workout is simply inconvenient. There are simple workarounds, like you mention above, to convert slope requests into usable power metrics. Therefore, Slope specification is fine. If bike vendors don’t offer the APIs needed to build complete structured workouts, I am not surprised. It is fair to say that 90% of smart bike and smart trainer sales are targeted at Zwift users. Slope mode can be offered as proof. I’ll never be fully aligned with this since I have absolutely zero interest in Zwift. I am perfectly aware that makes me the outlier .
Let’s take a step back and consider “When is a slope mode structured workout better than an erg mode workout?” I can summarize in one word: Acceleration. Any riding - and especially racing - involves countless accelerations. Hills, sprints and breakaways all require somewhat intense accelerations. Riders with power meters on their road bikes know what these look like:
Massive increase in power. Even old guys like me go from 200 watts to 800 watts in a sprint.
Insane rate of change. Watch the track racers in the Olympics. These riders go from 0 to 2kw in half a pedal stroke.
When I move indoors, I want to train for acceleration. I will never do a 2 hour ride indoors, so LSD training will have to wait for me to get back outdoors. Short, hard efforts with rapid transitions is the training plan I want. They now call it HIIT. We called it “weekly team sprints” in the 1980s. It remains the best training tool I have ever used - even now 40 years later.
Erg mode is really “anti-acceleration” mode. Every attempt to accelerate is met with a corresponding decrease in resistance. You can only imagine how ex-sprinters like me curse erg mode. Just when the workout is getting interesting, the bike turns to mush.
I will use slope mode in preference to erg mode almost exclusively. I will keep rider weight and FTP constant so I can have maximum control over workouts. I already do this with FTP in erg mode. I never change FTP. Why? I don’t want rest interval power to change when I increase the peak intervals. Also, I like to vary the length of the recovery intervals based on fitness and load factors. This means I hand edit training plans almost everyday. I will likely do the same with slope training. I can’t wait to get started.