Discussion (summarized by B. Schürch)

The BMR of a 3-year-old child is more than 50% of an adult's, yet its weight is only around 20% of an adult's; can all of this be explained in terms of organ growth? The question cannot be answered definitively, but the fact that, in young animals, muscle has a higher BMR per weight than in old animals would suggest that other factors play a role as well.

Changes in sleeping metabolic rate occur a few minutes before the change in sleep state (REM, non-REM); hormonal changes seem to be responsible for this phenomenon.

In Butte's studies, infants with a higher sleeping metabolic rate generally also had higher activity scores.

The SMR of an infant can be altered by 50% by ambient temperature; controlling ambient temperature is therefore important in the measurement of sleeping metabolic rate in infants.