Modeling the dose-response rate/associations between VO2max and self-reported Physical Activity Questionnaire in children and adolescents

Abstract

Background: This study sought to explore the dose-response rate/association between aerobic fitness (VO_2max) and self-reported physical activity (PA) and to assess whether this association varies by sex, age, and weight status.

Methods: VO_2max was assessed using the 20-m shuttle-run test. PA was assessed using the Physical Activity Questionnaire (PAQ) for Adolescents (aged >11 years, PAQ-A) or for Children (aged ≤11 years, PAQ-C). The associations between VO_2max and PAQ were analyzed using analysis of covariance (ANCOVA), adopting PAQ and PAQ² as covariates but allowing the intercepts and slope parameters of PAQ and PAQ² to vary with the categorical variables sex, age group, and weight status.

Results: ANCOVA identified a curvilinear association between VO_2max and PAQ, with positive linear PAQ terms that varied for both sex and weight status but with a negative PAQ² term of -0.39 (95% confidence interval (CI): -0.57 to -0.21) that was common for all groups in regard to age, sex, and weight status. These curvilinear (inverted U) associations suggest that the benefits of increasing PA (same dose) on VO_2max is greater when children report lower levels of PA compared to children who report higher levels of PA. These dose-response rates were also steeper for boys and were steeper for lean children compared to overweight/obese children.

Conclusion: Health practitioners should be aware that encouraging greater PA (same dose) in inactive and underweight children will result in greater gains in VO_2max (response) compared with their active and overweight/obese counterparts.

Keywords: Aerobic fitness; Curvilinear association; Sex; Slope parameters; Weight status.