This is a means of physical culture that has fallen by the wayside over the years, much like hand balancing. Muscle control involves flexing and relaxing
Control of Breathing - Lung and Airway Disorders - Merck Manuals Consumer Version
Strongman Profile: Maxick Teaches Us the Lost Art of Muscle Control - Breaking Muscle
What Causes Chest Muscle Strains and How to Treat It - PMIR
Scapular Dyskinesis: Conscious Muscle Control and Mass Movement Patterns – Adult and pediatric printable resources for speech and occupational therapists
Active Stretching by Neil Keleher [Leanpub PDF/iPad/Kindle]
Muscle Control - The Book Merchant Jenkins
Frictional Resistance
Original 1940s Book Muscle Control By Maxick – Mullard Antiques and Collectibles
Lumbar Motor Control Training - Physiopedia
Involuntary muscle - Definition and Examples - Biology Online Dictionary