The regular chanting of Lord's name with full concentration and other such activities as fondly thinking about Him, intensely listening to His pastimes purify our body by causing four physical impacts- a devotee may feel excessive sweat through which body toxins come out; often a sudden quirk is felt which cleans up our intricate nervous system; a divine thrill opens the clogged pores of the body and eyes start shedding tears.
Besides, there are advanced states of voice break (swar- bhang), throat block (kantha-avrodh), swoon (moorchha) and trance (smadhi).
In yogic terms, we should try reaching that stage through chanting wherein our breath begins to pass through Sushumna nadi. As per Goapl sahastra naam, breathing through Sushumna implies direct union with Lord Krishna and medically, our body hormones may even undergo a change in this process.