Abstract
Background Adolescents living with obesity (AlwO) can have limited
exercise capacity. Exercise capacity can be predicted by a 2-factor
model comprising lung function and leg muscle function, but no study has
looked at cycling leg muscle function and its contribution to cycling
exercise capacity in AlwO. Methods 22 nonobese adolescents and 22 AlwO
(BMI>95 percentile) were studied. Anthropometry, body
composition (DEXA), spirometry, 30-sec isokinetic work capacity, and
maximal exercise (cycle ergometry) were measured. Results AlwO had
greater lean leg mass (LLM) (14.8±4.1 vs 21.0±4.3 kg, Con vs AlwO
p<0.001). Lung function did not differ, although FEV
1 trended higher in AlwO (101.0±13.1 vs 107.9±12.7
percent predicted, p=0.08). Leg 30-second work output did not differ in
absolute terms or per allometrically scaled LLM. Peak oxygen consumption
did not differ between the groups in absolute terms or as percent
predicted values (78.5±15.4 vs 82.1±16.5 percent predicted), but was
lower in AlwO when expressed per scaled kg of LLM. Peak oxygen
consumption related to both lung function and 30-second work capacity,
with no observed group effect. 30-second leg work capacity related to
the scaled muscle mass, with a small group effect. There was some
correlation between leg work capacity and time spent in moderate to
vigorous physical activity in AlwO (r s=0.39, p=0.07).
Conclusion AlwO have larger LLM and preserved exercise capacity, when
expressed as percentage of predicted, but not per allometrically scaled
LLM. Increasing time spent in moderate to vigorous activity may benefit
AlwO.