Sorry to say but it’s probably a lose here for trainer road. You’re talking less than $1 per workout.
Think of a low volume plan with roughly 12 workouts a month which works to like $12. Why would you pay for the subscription?
I think you’d have to charge something like $6-8 per hr or per workout. This would make folks if they are dedicated users to pay for the sub after like 3 workouts.