Heavy Muscle was recorded and mixed by Phil Jones at The Dangler in Seattle, and mastered by Chris Mathews, Jr. The EP follows 2013 full-length Bremerton Zoo and 2011 EP Death Haunts, both also released on Twelve Gauge Records. Of Bremerton Zoo, UK blog Tight to the Nail opined: "The wild-eyed, antisocial, bloodied knuckles and beer-stained jeans flipside to the old school hardcore coin... Drawing influence from Black Flag with their anarchic and raw fuck-you-core, Power have created a vicious and unpredictable record."