School of Human Sciences, The University of Western Australia, Crawley, Western Australia, Australia.
Am J Hum Biol. 2019 Jul;31(4):e23247. doi: 10.1002/ajhb.23247. Epub 2019 Apr 21.
The human juvenile period evolved as a period of learning and physical development in a family environment that subsidizes the costs of these processes. Children allocate energy to physical activity, maintenance, and growth. How energy is allocated has consequences for adult body size and other life-history traits. In subsistence agriculture populations, where child contributions to the household economy are common and energy availability is low, trade-offs in energy expenditure between activity and growth may help explain poor growth.
Using accelerometry, we measured physical activity over 2 years in 88 free-living children aged 5-19 years in two ecologically varying communities in rural Timor-Leste. We model characteristics related to variation in activity, and subsequently, activity is modeled against growth, illness, and aspects of household and local ecology using linear mixed models.
Physical activity in Timorese children is characterized by high levels of moderate ( = 8.8 h/day), no sustained vigorous, and little sedentary activity ( = 4.6 h/day). Children in the mountainous community show a slight trade-off between activity and growth (P = .077). Males down-regulate both growth and activity relative to females. Variation in household characteristics does not predict child activity. Both activity and growth are lower in the mountainous community than in the flat, coastal community.
Household demands on child behavior may constrain children's ability to moderate activity relative to nutritional status. Activity in this population is high relative to other subsistence populations, possibly because children face the dual pressures of contributing to household subsistence and attending school.
人类的青少年时期是在家庭环境中学习和身体发育的时期，家庭为这些过程提供资金支持。儿童将精力分配到体力活动、维持和生长上。能量的分配方式对成人的体型和其他生活史特征有影响。在以农业为生的人群中，儿童为家庭经济做出贡献是很常见的，而且能量供应也很低，因此在活动和生长之间的能量支出权衡可能有助于解释生长不良的原因。
我们使用加速度计在东帝汶农村的两个生态环境不同的社区中，对 88 名 5-19 岁的自由生活儿童进行了为期 2 年的身体活动测量。我们对与活动变化相关的特征进行建模，然后使用线性混合模型将活动与生长、疾病以及家庭和当地生态的各个方面进行建模。
帝汶儿童的身体活动以高水平的中度活动为特征（ = 8.8 小时/天），没有持续的剧烈活动，也没有久坐活动（ = 4.6 小时/天）。山区社区的儿童在活动和生长之间表现出轻微的权衡（P = 0.077）。男性相对于女性，在生长和活动方面都有所下调。家庭特征的变化不能预测儿童的活动。山区社区的活动和生长都低于沿海平原社区。
家庭对儿童行为的要求可能限制了他们根据营养状况来调节活动的能力。该人群的活动水平相对其他以农业为生的人群较高，这可能是因为儿童面临着为家庭生计做出贡献和上学的双重压力。
