What is commonly associated with jet lag?

Jet lag is primarily associated with a disruption in the body's internal clock, or circadian rhythms, that occurs after traveling across multiple time zones. This disruption can lead to a variety of symptoms, including fatigue, difficulty concentrating, and disturbances in sleep patterns. Cardiac dysrhythmia can occur as a result of the stress that jet lag places on the body, influencing heart rate and rhythm due to changes in sleep, stress levels, and physiological responses during travel.

The other options imply positive effects or improvements that do not typically correlate with the experience of jet lag. Increased alertness and heightened energy are not commonly associated with jet lag; rather, individuals often experience a decrease in these states due to fatigue and disorientation. Similarly, improved metabolism is not a recognized effect of jet lag; instead, the body's metabolic processes can be negatively impacted by the stress and irregular sleep patterns associated with rapid travel across time zones.