What is a characteristic of the muscle effects caused by ketamine?

The muscle effects caused by ketamine are characterized by increased muscle tone, particularly in the initial stages after administration. Ketamine is known to produce a dissociative anesthetic state that can induce a form of catalepsy, which can lead to increased rigidity and augmented muscle tone. This phenomenon is particularly evident when ketamine is used at certain doses, leading to a state where the patient may experience heightened muscle activity or rigidity instead of relaxation.

In contrast, the other options describe effects that do not align with the pharmacological profile of ketamine. For instance, decreased muscle tone or muscle paralysis would reflect a relaxation or loss of function in the muscle tissue, which is contrary to the increased muscular activity induced by ketamine. Furthermore, controlled muscle contractions suggest a level of voluntary or modulated muscular control, which does not accurately represent the characteristic effects of ketamine.

Thus, the correct characteristic associated with ketamine is the increased muscle tone experienced in the treatment setting.