Which age group has the fastest average heart rate compared to other age stages specified?

Infants have the fastest average heart rate compared to other age groups due to several physiological reasons. In the early stages of life, particularly during infancy, the body's metabolic demands are higher, which results in an elevated heart rate. This is necessary to support growth, development, and the higher oxygen needs of an infant's tissues and organs.

As children grow and develop into adolescents and young adults, their heart rates generally decrease as their bodies become more efficient at circulating blood and meeting metabolic needs. Adults typically have the slowest resting heart rates among these age groups, as their cardiovascular systems are fully developed and more efficient. Thus, the average heart rate of infants stands out as being significantly higher than that of preschoolers, adolescents, and adults, reflecting their developmental stage and metabolic requirements.