Dissertation Defence: The Influence of Maturation and Sex on Sedentary Time, Physical Activity and Lower Limb Vascular Function in Children and Adolescents

Kate Sansum, supervised by Dr. Ali McManus, will defend their dissertation titled “The Influence of Maturation and Sex on Sedentary Time, Physical Activity and Lower Limb Vascular Function in Children and Adolescents” in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Kinesiology.

An abstract for Kate Sansum’s dissertation is included below.

Examinations are open to all members of the campus community as well as the general public. Please email ali.mcmanus@ubc.ca to receive the Zoom link for this exam.

Abstract

Research on the effects of maturation and sex on sedentary time, physical activity (PA), and lower limb vascular health is limited, but crucial for shaping guidelines for children and adolescents. This dissertation investigated how maturation and sex influence sedentary time, PA, and vascular function. Differences in sex and maturity for weekday and weekend sedentary time accumulation, and associations with cardiometabolic risk factors were explored. While children and adolescents exhibit different sedentary time patterns, no sex or maturity differences were identified. Sedentary bouts lasting over an hour were uncommon, particularly on weekdays. Sit-to-stand transitions were associated with lower systolic blood pressure and body fat percentage, indicating that frequent breaks in sitting may benefit cardiometabolic health. This dissertation also explored sex and maturity differences in superficial femoral artery function. Participants who had not reached peak height velocity (PHV) had higher vascular function than those who had passed PHV, with no sex differences observed. This difference diminished after allometric scaling, underscoring its significance in paediatric research. The relationships between stationary time, PA, stationary bout durations, and cardiorespiratory fitness with vascular function were also investigated. Light-intensity PA and total PA were inversely related to vascular function, whereas stationary time showed a positive association. These findings may reflect the problems with physical inactivity, with only 23% of participants meeting the PA guidelines. Given the sedentary bout patterns identified in study one, the final study assessed the impact of one hour of uninterrupted sitting on lower limb vascular function in pre-pubertal children, adolescents, and adults. Sitting significantly reduced vascular function, with no differences in the response between sex or maturity groups.