Add or change strength exercises mid workout
Very often weights or a machine are being used and we need to swap the planned exercise for something similar. Like the BB bench is busy, so we can do DB bench press instead. Or we want to add something we didn't program previously.
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Shawn commented
You can do this on the PC/Desktop side of things, but I'd love to see it in mobile as that's where the athletes seem to interface with it the most. I run into this situation a lot and often give my athletes some options in the instructions, but there's no practical way to implement it on mobile (yet). It also opens up more flexible programming on the coaching side as you can give options to your athletes to keep them from getting bored.