Hey everyone. I was going to start a thread on this exact topic . Good to see.
I like Erg Mode for some structured workouts. The use case is: “I want a % FTP that translates to a particular amount of work over a given time interval”. Remembering that power = torque * rpm we end up with torque = rpm / power. If we agree that torque is the “resistance I feel at the pedals”, then resistance is constantly changing based on my pedalling speed. Faster pedalling = less torque and slower pedalling = more torque. Erg mode is great for many things - especially coaches who want to specify a power number and let the bike get the rider to do the correct amount of work.
Sprint Interval Training is a different goal: “Given a specific gear or resistance level, what’s the maximum power I can achieve and/or hold over a given time interval?” For any given gear, power = torque * rpm. If we agree that a gear translates to a measure of resistance applied to the pedals (optimally based om rider weight) then the power metric we are looking for is obtained by resistance * rpm. The higher the rpm, the happier I am .
I think Free-ride mode is the starting point. Instead of requiring me to manually select a virtual gear and watch the power reading, TrainerDay could set a virtual gear during each block based on %FTP or watts. I can increase or decrease resistance with the -/+ 100% control. I still watch the power readings but I don’t need to worry about resistance. I don’t do Zwift but I think this is a good description of their slope mode. I can’t find resistance training in any other smart bike software. My NordicTrack S22i spin bike had a programmable resistance mode that changed only resistance. I used it all the time.
Erg mode is good. Free-ride sprints are still the best for me, even if I have to manually set my resistance.