Final answer:
The liver, pancreas, spleen, and kidneys are not directly involved in voluntary movement but support bodily functions that indirectly contribute to muscle health and function. Voluntary muscles, controlled by individual will, are mainly skeletal muscles that are part of the motor system.
Step-by-step explanation:
The organs listed are all important for various bodily functions, but they do not have direct roles in voluntary movement. Voluntary muscles are those that can be controlled by an individual's will, such as skeletal muscles that facilitate movement like walking or lifting. These muscles are primarily involved in locomotion and maintaining posture and are controlled by the motor system, including the motor cortex, cerebellum, and basal ganglia.
The liver, pancreas, spleen, and kidneys are accessory organs or are part of other systems like the urinary system (for kidneys) that do not directly control voluntary movement. Instead, organs like the liver and pancreas play vital roles in digestion and metabolism, while the spleen is involved in filtering blood and the kidneys in removing waste and balancing bodily fluids. These organs may indirectly affect muscle function by maintaining overall health and ensuring that the muscles receive the nutrients and oxygen they need to function properly.