Muscle tone refers to the partial contraction present in a muscle at rest and the resistance to stretch when passive. It exists on a continuum from flaccidity with no muscle fiber firing to hypertonicity with high levels of fiber firing. Tone is dynamic and influenced by both intrinsic muscle properties and reflexes. It can describe a single muscle, group of muscles, limb, or entire body and is generally subjective to measure. Factors like emotions, health, and arousal can impact one's usual tone range.