What constitutes a "malevolent touch" by a prison guard as an actionable violation of the Eighth Amendment?

While malicious and sadistic uses of force always violate contemporary standards of decency, not every "malevolent touch" by a prison guard is actionable as an Eighth Amendment violation. Id. at 9. "The Eighth Amendment's prohibition of cruel and unusual punishment necessarily excludes from constitutional recognition de minimis uses of physical force, provided that the use of force is not of a sort repugnant to the conscience of mankind." Id. at 9-10 (internal quotation marks and citations omitted). What violates the Eighth Amendment is "the unnecessary and wanton infliction of pain," i.e., infliction of suffering that is "totally without penological justification." Rhodes v. Chapman, 452 U.S. 337, 346 (1981).