Changes in time-segment specific physical activity between ages 10 and 14 years: A longitudinal observational study.

Area of Science:

• Pediatric Exercise Science
• Adolescent Health Behaviors
• Physical Activity Epidemiology

Background:

• Physical activity (PA) levels typically decline during adolescence.
• Understanding time-segment specific changes in PA is crucial for developing targeted interventions.
• Previous research has not fully elucidated PA changes across diverse daily contexts during this developmental period.

Purpose of the Study:

• To describe changes in moderate-to-vigorous PA (MVPA) and total PA (TPA) across specific time segments during adolescence.
• To compare PA changes between different time segments (weekdays vs. weekends, in-school vs. out-of-school, etc.).
• To examine the association between changes in time-segment specific PA and overall PA decline.

Main Methods:

• A longitudinal observational study followed 769 children (42% boys) for 4 years, measuring PA via accelerometry at ages 10, 11, and 14.
• Mixed-effects linear regression models analyzed changes in MVPA and TPA across weekdays, weekends, in-school, out-of-school, lesson times, and lunch times.
• Time-segment specific changes were compared using interaction terms, and associations with overall PA changes were assessed.

Main Results:

• MVPA and TPA generally declined across all measured time segments, with the exception of lesson-time MVPA.
• Greater annual declines in MVPA and TPA (for boys) were observed on weekends compared to weekdays, and out-of-school compared to in-school periods.
• Significant declines were also noted during lunch-time compared to lesson-time, and out-of-school compared to in-school periods for TPA.

Conclusions:

• Physical activity (PA) maintenance interventions during adolescence should consider all time segments.
• Weekends and out-of-school periods represent particularly critical times for intervention due to substantial PA declines.
• Targeting these specific periods may be more effective in mitigating overall PA reduction throughout adolescence.