Physical activity levels and child growth

What happens when physical activity levels in a community decrease drastically as a result of big transformation of a traditional agricultural economy to a mechanized society? Scientists at the CUNY Hunter College, New York, and University of Utah, Salt Lake City have come up with a conclusion that sizable increases in mean height, weight, and triceps skin fold thickness have taken place in growing children. Samuel S. Urlacher and Karen L. Kramer have reported their findings in Nature (2018) and remarked that such a transition occurred in Yucatec Maya agriculturalists over a span of 20 years. The situation witnessed declines in Physical Activity Levels (PAL) of growing children in post modernised society. How this has happened ? According to them roads were built, water supply and electricity were introduced; health clinics and modern schools were opened. All these amenities were introduced quickly at a large scale. As a result the children had enough free time, with a very little Physical Activity Levels (PAL). They saved hundreds of calories which were used in increasing the height, weight and skin folds during the process of growth and thus resulting in secular growth shifts during this period. Earlier studies indicated that physical activity is an important factor for a favourable growth of children. However, this study takes on the earlier studies and raises a conflicting point of view. Here the big question is how much of Physical Activity Levels (PAL) are required for favourable growth of children. The findings of this study, if proved true by a number of studies on similar grounds, would open new avenues in the field of child growth and development.