for convienience once a week does it, but since i love how my muscles look when i spot inject, id do one cc in each shoulder twice a week on the days i was going to be hitting my delts, chest, and tri's . but if u dont train like me or if i were to do the typical once a week body hits, i would hit delts on the day i normally hit them and then 2-4 days later to keep the fascia stretching