Tomorrow I have Log In to TrainerRoad planned. Last week I had Guard and it didn’t really work well in ERG mode, so maybe this week I’ll try in resistance mode. Last workout I tried switching from ERG to resistance but found out I quickly ran out of gears, so which gear and chainring do I start in when starting a workout in resistance mode (shimano semi-compact and 11s 12-25 cassette)
edit: incidentally the work intervals of both these workouts are 2:06 not 2:00 and rests 3:54 not 4:00 as in the description text
For starting, you can check out the support section on Resistance mode.
Key here is finding a Resistant percentage setting that is appropriate for you. The trainer in use, gearing on your bike and even your FTP relative to your trainer capabilities will all lead to a potential different setting.
I find that Resistance around 20-40% can work well for many trainer and gearing setups. But experiment as needed of that is not enough Resistance in use.