Hi, my husband has three herniated disks in his back and is in severe pain, he can’t even walk, would he be able to use a Thera gun on his back over Shabbat?

The Thera Gun runs on batteries, and accordingly, in his situation, he can have a gentile give him this treatment on Shabbat. May he have a refuah shleima b'toch sha'ar cholei Yisrael!