Table Structure: 2 Related Entities Share the Same Entity
Try it like this:
general table:
general_id/user_id/set_id/workout_id/Reps/Weight
In your select query you can then do something like this:
SELECT concat(u.name, ' , u.last_name) as user,
       s.set,
       w.workout,
       g.reps,
       g.weight
FROM general_tbl g JOIN user u ON u.id_user = g.id_user 
                   JOIN set s ON s.id_set = g.id_set
                   JOIN workout w ON w.id_workout = g.id_workout