Atonia is a medical term that refers to a state of muscle weakness or lack of tone in the body. The antonyms for atonia are words that represent the opposite condition. Some possible antonyms include tonicity, strength, vigor, vitality, firmness, and tension. Tonicity is the ability of muscles to contract and maintain a steady level of tension. Strength refers to physical power, endurance, and capability. Vigor and vitality denote energy, robustness, and vitality. Firmness refers to the quality of being strong, solid, and unyielding. Tension is the feeling of tightness, rigidity, or stress. By understanding the antonyms of atonia, we can better appreciate the importance of muscle tone and its role in bodily movement and health.