tonía

Tonía is a term derived from the Greek tonos, meaning tension or tone. In medical and biological usage, it refers to the baseline level of tension or resistance to passive movement in muscles and other tissues. It is a fundamental aspect of motor control and posture, maintained by the nervous system.

In humans and many animals, tonía exists even at rest and is continuously regulated by motor nerve activity, reflexes, and the intrinsic properties of muscles. It provides readiness for action and helps stabilize joints, enabling smooth motor execution.

Clinical evaluation of tonía includes observation of resistance to passive movement, posture, and reflex tone. Quantitative methods such as surface electromyography (EMG) can aid in characterizing tone levels. Abnormal tonía is commonly described as hypotonia (reduced muscle tone) or hypertonia (increased muscle tone). Hypotonia can present as floppy limbs and diminished resistance to movement and may accompany developmental or neuromuscular conditions; hypertonia can cause stiffness and restricted range of motion and is seen in various neurological disorders.

In newborns, tonía is an important indicator of neuromotor integrity and can inform assessments of developmental progress. In adults, changes in tonía may follow injury, disease, or aging, affecting balance and motor performance.

Outside medicine, tonía can appear in discussions of tonal quality in acoustics or phonology or in music, where the term refers to tone in a broader sense. In those contexts, more specific terms such as tono, entonación, or tono musical are typically used.