Swap for a move that trains the same muscle in the same pattern, like leg press for squat or dumbbell press for barbell bench.
The quick answer
Replace it with an exercise that hits the same primary muscle through the same movement pattern. Can't back squat, use leg press or a goblet squat; no pull up bar, use lat pulldown or inverted rows; barbell bench bothers your shoulder, try a slight incline dumbbell press. Match the rep range and progress it the same way you would the original.
How to think about it
Match muscle and pattern
Identify what the lift trains and how. Barbell rows and dumbbell rows, both horizontal pulls for the back, are interchangeable. Overhead press and machine shoulder press both load the front delts. Keep the pattern and you keep the training effect.
Common substitutes
Barbell squat becomes leg press, hack squat, or split squat. Deadlift becomes Romanian deadlift or hip thrust. Dips become close grip press. Pull ups become lat pulldown. Pick the version your equipment and joints allow.
Keep progressing
Once swapped, treat it like any working lift: same rep target, add load or reps over time. SUUPR lets you sub an exercise in a routine and carries your logging forward so progression stays intact.
Do this
Name the target muscleDecide the main muscle the original trains before picking a replacement.
Keep the patternChoose a push for a push, a hinge for a hinge, so the movement quality matches.
Match the rep rangeIf the original was 5s, keep the sub in a similar range rather than switching to high rep.
Test it lightRun the new exercise light first to check it feels right on your joints.