Asthenia is best defined as:

Asthenia is best understood as a condition characterized by generalized muscle weakness. This term refers specifically to a reduction in strength or an overall lack of energy and vitality, which can impact a person's ability to perform regular physical activities.

In many instances, asthenia may be a symptom of an underlying medical issue or condition, such as muscle diseases or systemic disorders, leading to the inability to sustain physical efforts. It is distinct from terms that might describe other physical limitations or symptoms, such as stiffness or coordination challenges. By recognizing asthenia as generalized muscle weakness, healthcare providers can better assess a patient's condition and determine appropriate interventions or treatments. Understanding this definition is crucial for differentiating asthenia from other similar-sounding conditions or symptoms that affect movement or physical capabilities.