This function only returns one value to all records

This function only returns one value to all records

Hi,

I built this function to update a field in form with the text name of the lookup field in that same form.  This works... except that for every record, it is updating the same lookup field name to all fields, instead of the correct lookup field for that record.  So instead of getting the correct Single Workout Name for each record, I get the same one for ALL records.  I am missing a part of the code that pulls from the same record and update that same record.  

I am not sure what I am missing.  Can someone help?

void test2()
{
exercise = Add_Exercise_M1W3[ID != 0];
SingleWorkoutToText = Add_Single_Workouts[ID == exercise.Single_Workout];
for each  r in Add_Exercise_M1W3
{
r.Single_Workout_to_Text=SingleWorkoutToText.Single_Workout_Name;
}
}