Hormonal and Metabolic Responses to a Resistance Exercise Protocol in Lean Children, Obese Children, and Lean Adults

During childhood, varying exercise modalities are recommended to stimulate normal growth, development, and health. This project investigated hormonal and metabolic responses triggered by a resistance exercise protocol in lean children (age: 9.3 +/- 1.4 y, body fat: 18.3 +/- 4.9%), obese children (age: 9.6 +/- 1.3 y, body fat: 40.3 +/- 5.2%) and lean adults (age: 23.3 +/- 2.4 y, body fat: 12.7 +/- 2.9%). The protocol consisted of stepping onto a raised platform (height = 20% of stature) while wearing a weighted vest (resistance = 50% of lean body mass). Participants completed 6 sets of 10 repetitions per leg with a 1-min rest period between sets. Blood samples were obtained at rest preexercise, immediately postexercise and 2 times throughout the 1-hr recovery to analyze possible changes in hormones and metabolites. Children-adult differences included a larger exercise-induced norepinephrine increase in adults vs. children and a decrease in glucagon in children but not adults. Similarities between adults and children were observed for GH-IGF-1 axis responses. Metabolically, children presented with lower glycolytic and increased fat metabolism after exercise than adults did. Obesity in childhood negatively influenced GH, insulin, and glucose concentrations. While adults occasionally differed from children, amount of activated lean mass, not maturation, likely drove these dissimilarities.