spot injects do nothing to help growth in the site injected, period, if that's what you're referring to. the one Anabolic Androgenic Steroids (AAS) where there is some debate is test suspension. that one is arguable. other than that ONE, i have yet to see a single good argument to show spot injecting for local size increase really works to any great degree.
like they said, site injecting is used to give frequently injected sites a rest and time to heal before scar tissue is formed.