The effects of an after-school intervention program on physical activity level, sedentary time, and cardiovascular risk factors in adolescents

Abstract Aim: To ascertain the effects of an after-school intervention on physical activity levels and cardiovascular risk factors in adolescents from Campinas, Brazil. Methods: This was an intervention study with 71 adolescents that was carried out in two schools, randomly assigned to a control group (CG:n=45) or an intervention group (IG:n=26). We performed evaluations of body composition, sexual maturation, blood pressure, level of physical activity, sedentary time (ST), and eating habits, as well as biochemical variables by a portable analyzer. The IG participated in two weekly sessions of physical activities and controlled physical exercises for 14 weeks. The sessions lasted 60’, and were divided into warm-up (5-10’), main part (40-50’), and recovery (5-10’). Results: 30.8% of the IG and 24.4% of the CG were classified as overweight/obese. Additionally, the IG showed significantly lower ST (total: p=0.037; daily: p=0.009) after the intervention, as well as in the post-period (total ST: p=0.043; daily ST: p=0.007). The IG showed a reduction in glycemia (p=0.025). Conclusion: The intervention program generated positive changes in glycemia levels and ST. These results suggest that interventions involving physical exercise should be promoted in the school environment, as physical activity is an important component of a healthy lifestyle.摘要：本研究旨在明确巴西坎皮纳斯市青少年课后干预措施对其身体活动水平与心血管危险因素的影响。 研究方法：本研究为纳入71名青少年的干预性研究，在两所学校开展，受试者被随机分为对照组（control group, CG：n=45）与干预组（intervention group, IG：n=26）。研究人员对受试者的身体成分、性成熟状态、血压、身体活动水平、久坐时长（sedentary time, ST）与饮食习惯，以及通过便携式分析仪检测的生化指标开展了评估。干预组每周进行两次身体活动与控制性体能训练，持续14周，单次训练时长为60分钟，分为热身（5~10分钟）、主训练环节（40~50分钟）与放松恢复（5~10分钟）三个部分。 研究结果：干预组与对照组中分别有30.8%与24.4%的受试者被归类为超重/肥胖。此外，干预组在干预后久坐时长显著降低（总久坐时长：p=0.037；日均久坐时长：p=0.009），干预后随访阶段的久坐时长同样显著低于干预前水平（总久坐时长：p=0.043；日均久坐时长：p=0.007）。干预组受试者的血糖水平出现显著降低（p=0.025）。 研究结论：本干预项目可对血糖水平与久坐时长产生积极改善效果。上述结果提示，学校环境中应推广包含体能锻炼的干预措施，因为身体活动是健康生活方式的重要组成部分。