Recommended 24-h movement behavior patterns and equivalent impacts on mental health among Chinese adolescents: a...

To investigate an optimal 24-h movement behavior recommendation framework to promote mental health and evaluate its equivalent impacts on these psychological outcomes.

A sample of 319 junior high school students (mean age: 13.73 years, 52.6% male) from Chengdu, China, were included in the study. Their 24-h movement behaviors, comprising light physical activity (LPA), moderate-to-vigorous physical activity (MVPA), sedentary behavior (SB), and sleep (SLP), were objectively measured using accelerometers combined with sleep logs. Psychological wellbeing and anxiety were assessed using the Adolescent Wellbeing Scale and the Chinese version of the Multidimensional Anxiety Scale for Children (MASC-C), respectively. Compositional linear regression, the optimal time-use zone analysis, time reallocation analysis, and equivalent impact curves were applied to systematically examine the relationships between 24-h movement behaviors and mental health outcome.

The overall 24-h movement behavior composition was significantly associated with both psychological wellbeing and anxiety scores. Relative to the remaining behaviors, LPA (β = 6.109, P = 0.028) and SLP (β = 18.610, P = 0.004) were positively associated with psychological wellbeing, whereas SB (β = -24.476, P < 0.001) was negatively associated with psychological wellbeing. For anxiety, SB (β = 32.000, P < 0.001) was positively associated with anxiety scores, whereas MVPA (β = -6.353, P = 0.029) and SLP (β = -25.827, P = 0.009) were negatively associated with anxiety scores. To optimize overall mental health, the recommended durations and ranges for 24-h movement behaviors were 316 min/day (270-420 min/day) for LPA, 68 min/day (50-110 min/day) for MVPA, 510 min/day (460-550 min/day) for SB, and 545 min/day (470-610 min/day) for SLP. Under the one-to-three isoproportional substitution model, three compositional time-reallocation patterns were estimated to correspond to a predicted 0.1-standard deviation (SD) higher psychological wellbeing score: a relative increase in LPA (+ 56.5 min/day), a relative decrease in SB (-26.2 min/day), or a relative increase in SLP (+ 31.8 min/day). Under the one-to-one isotemporal substitution model, a comparable predicted difference was observed when reallocating 27.9 min/day of SB to LPA or 24.7 min/day of SB to SLP. For anxiety, the corresponding one-to-three isoproportional substitution patterns associated with a predicted 0.1-SD lower anxiety score were a relative increase in MVPA (+ 19.4 min/day), a relative decrease in SB (-28.5 min/day), or a relative increase in SLP (+ 32.6 min/day). Similarly, under the one-to-one isotemporal substitution model, a comparable predicted reduction was estimated when reallocating 26.1 min/day of SB to SLP.

For junior high school students, the recommended daily durations of 24-h movement behaviors for overall mental health were316 min of LPA, 68 min of MVPA, and 545 min of SLP, while SB should be limited to no more than 550 min per day. Beyond these specific durations, comparable predicted mental health profiles may correspond to multiple behavioral time-reallocation patterns. In particular, relative reductions in SB showed the strongest magnitude of association with favorable mental health outcomes.