electrical muscle stimulator

there are devices availble in the physitherapy market known as ems or electronic muscle stimulator. 20 channel machine available in amazon . the output at present is limited to 10 mA - 30 m A. i want to increase it to 60 mA. Presently it is biphasic sqaure wave form. i want to make it monophasic with frequency in range of 1000 to 5000 hz