What health effect is particularly associated with exposure to microwave radiation?

Exposure to microwave radiation is primarily associated with increased heart rate due to the way microwaves interact with biological tissues. Microwaves can generate heat within the body, which can lead to physiological responses, including variations in heart rate as the body reacts to the warmth. When microwave energy is absorbed, especially at certain power densities, it can lead to thermal effects that reflect the body's response to excess heat, thereby causing an increase in heart rate as the body attempts to manage the elevated temperatures and maintain homeostasis. Understanding this relationship is crucial for assessing potential health risks related to microwave exposure, particularly in occupational settings where exposure levels might be higher.

The other options do not correlate with the known effects of microwave radiation exposure. For instance, enhanced vision, decreased metabolic rate, and improved digestion are not established health outcomes related to microwave radiation.