You don't redo a routine; you edit it. Open the routine, tap the input bar, and describe what to change.
Things you can say
Swap exercises: "Swap the burpees for mountain climbers."
Change length: "Make it 15 minutes shorter." / "Make it 45 minutes."
Change focus: "Add more core work." / "More mobility, less strength."
Change intensity: "Make it harder." / "Dial it back — easier version."
Add constraints: "No jumping." / "Bodyweight only, no equipment."
Structural changes: "Add a five-minute cool-down at the end."
Ask for explanations: "Why did you pick these exercises?"
What happens
The routine updates in place — you'll see it re-build with your change applied. The conversation remembers prior context, so you can keep refining across multiple edits.
Edit by voice too
The mic works here as well. Speak the change instead of typing it.
When edits feel "off"
If an edit produces a result that isn't quite right, try being more specific:
"Swap the burpees" → "Replace the burpees with something low-impact for the knees."
"Make it shorter" → "Make it 20 minutes total, cut some of the accessory work."
You can always revert by asking: "Undo that last change" — though it's often faster to just re-describe what you want.