Allow timed sets for an exercise (ie. 1 minute of planks or squats)
If an exercise is time based give me the option to enter time rather than defaulting to reps. For example, plank asks for reps but it makes more sense to enter that I did plank for 60 seconds.
Tim Oyediran commented
For Front plank allow reps count in addition
A timer or stop watch so when. My trainer says do an exercise for 30 secs and then rest for a min. I can do without exiting the app