Impact of Combined Theory-Based Intervention on Psychological Effects and Physical Activity among Chinese Adolescents

The current study was intended to assess the effect of a facilitated behavioral intervention based on the extended theory of planned behavior (TPB) on psychological constructs and physical activity among adolescents over a period of eight weeks.

Students (n = 51, 12 ± 0.3 years of age) in the seventh grade at a junior middle school in China were randomly assigned to two groups: the intervention group (n = 24) and the control group (n = 27). Both groups were pre- and post-tested with the related psychological constructs of the extended TPB, along with behavioral measures of the Physical Activity Scale and ActiGraph accelerometer (model wGT3X-BT). The intervention group took part in 45 min classes once per week for 8 weeks, including five indoor theoretical courses and three outdoor basketball matches. The control group was not required to make any change to their normal school day. Also, 2 × 2 repeated measures analysis of variance (ANOVA) was conducted to compare the differences between the two groups, and then t-test was employed to compare the independent and paired differences.

Significant increases in pre-post subjective norms (SN) (p = 0.041, Cohen's d = 0.62), perceived behavior control (PBC) (p = 0.023, Cohen's d = 0.72), exercise intention (EI) (p = 0.043, Cohen's d = 0.61), and self-efficacy (SE) (p = 0.035, Cohen's d = 1.36) were observed in the intervention group. In addition, participants in the intervention group increased their exercise frequency (p < 0.001, Cohen's d = 1.25) and intensity (p = 0.028, Cohen's d = 0.68), especially their time spent on light intensity physical activity (light-PA%; p = 0.031, Cohen's d = 0.68), and their percentage of sedentary time (SB%) was also reduced (from 68% ± 10% to 58% ± 7%, p < 0.001, Cohen's d = 1.17). Furthermore, the intervention group showed significantly better performance in PBC (p = 0.032, Cohen's d = 0.62), EI (p < 0.001, Cohen's d = 1.32), SE (p < 0.001, Cohen's d = 1.15), SB% (p < 0.001, Cohen's d = 1.22), light-PA% (p < 0.001, Cohen's d = 1.12), and total physical activity (TPA) (p = 0.015, Cohen's d = 0.72) compared to the control group at the post-test. No significant pre post differences were observed for any psychological or behavioral variables in the control group, except for exercise frequency, but the values were still lower than those in the intervention group after the 8-week intervention (3.70 ± 0.72 versus 3.92 ± 0.83).

The combined theory-based intervention was effective at improving psychological constructs and physical activity among seventh-grade adolescents in 8 weeks.