卫生研究

目的 探究大学生24小时活动行为与健康体适能的关联及替代效应。方法 于2023年5—6月采用方便抽样与随机抽样相结合的方法，选取天津科技大学325名在校本科生作为研究对象，其中男生167人，女生158人。使用三维加速度计(ActiGraph GT3X+)测量24小时活动行为，包括中等强度身体活动(moderate-intensity physical activity, MPA)、高强度身体活动(vigorous-intensity physical activity, VPA)、低强度身体活动(light-intensity physical activity, LPA)、久坐行为和睡眠时间。体成分通过体质指数(body mass index, BMI)、腰围、体脂率衡量，肌肉力量通过握力衡量，心肺耐力通过肺活量和最大摄氧量(maximum oxygen uptake, VO_{2 max})衡量，柔韧性通过坐位体前屈衡量。使用成分分析方法分析探讨各行为与健康体适能的关系，并以15 min建立等时替代模型预测各活动行为替代后对结局变量产生的影响。结果 男生年龄(19.74±1.16)岁，女生为(19.51±1.29)岁。基于24小时活动行为成分分析，大学生日均MPA时间为16.42 min(1.14%),VPA时间为26.57 min(1.85%),LPA时间为150.92 min(10.48%),久坐时间为645.78 min(46.05%),睡眠时间为561.31 min(40.21%)。在控制性别、年龄等协变量后，成分等时替代模型显示：增加MPA时，BMI下降0.07～0.19个单位，体脂率下降0.53～0.59个单位，腰围下降0.16～0.27个单位，肺活量增加119.18～152.67 mL,VO_{2 max}增加1.76～1.88 mL/(kg·min),握力增加0.86～1.46 kg,坐位体前屈增加0.19～0.38 cm。增加VPA时，BMI下降0.14～0.16个单位，体脂率下降0.49～0.54个单位，腰围下降0.12～0.23个单位，肺活量增加127.45～160.84 mL,VO_{2 max}增加1.91～2.03 mL/(kg·min),握力增加0.98～1.56 kg,坐位体前屈增加0.14～0.32 cm。增加LPA时，BMI上升0.11～0.12个单位，握力增加0.65 kg,坐位体前屈增加0.21 cm。增加睡眠时间时，BMI下降0.04个单位，腰围下降0.09个单位。结论 MPA对BMI、体脂率、腰围改善最为显著，VPA在提升心肺耐力、肌肉力量和柔韧性方面效果更佳。睡眠时间对BMI与腰围具有正向作用，但替代效应弱于MPA与VPA;久坐行为和LPA则普遍不利于体质健康发展。

OBJECTIVE This study examined the associations between 24-hour movement behaviors and health-related fitness in university students, and estimated the substitution effects using a compositional isotemporal substitution model.METHODSThis study was conducted between May and June 2023, using a combination of convenience and random sampling to recruit 325 undergraduate students from Tianjin University of Science & Technology as participants, including 167 males and 158 females. Daily 24-hour activity behaviors were measured using a triaxial accelerometer(ActiGraph GT3X+), including moderate-intensity physical activity(MPA), vigorous-intensity physical activity(VPA), light-intensity physical activity(LPA), sedentary behaviors(SB), and sleep(SLP) duration. Body composition was assessed via body mass index(BMI), waist circumference, and body fat percentage. Muscular strength was measured by handgrip strength, cardiorespiratory fitness was measured by vital capacity and maximum oxygen uptake(VO_{2 max}), and flexibility was assessed by the sit-and-reach test. Compositional data analysis was used to investigate the associations between activity behaviors and health-related physical fitness. A 15-minute isotemporal substitution model was applied to predict the effects of replacing one activity with another on outcome variables.RESULTS The mean age of male participants was(19.74±1.16) years, and that of female participants was(19.51±1.29) years. Based on 24-hour compositional activity behavior analysis, college students spent an average of 16.42 minutes(1.14% of the day) in MPA, 26.57 minutes(1.85%) in VPA, 150.92 minutes(10.48%) in LPA, 645.78 minutes(46.05%) in SB, and 561.31 minutes(40.21%) in SLP. After adjusting for covariates including sex and age, isotemporal substitution models revealed that replacing an equivalent amount of sedentary time with MPA was associated with a reduction in BMI by 0.07-0.19 units, body fat percentage by 0.53-0.59 units, waist circumference by 0.16-0.27 cm, an increase in vital capacity by 119.18-152.67 mL, VO_{2 max} by 1.76-1.88 mL/(kg·min), handgrip strength by 0.86-1.46 kg, and sit-and-reach performance by 0.19-0.38 cm. Similarly, increasing VPA led to decreases in BMI by 0.14-0.16 units, body fat percentage by 0.49-0.54 units, waist circumference by 0.12-0.23 cm, increases in vital capacity by 127.45-160.84 mL, VO_{2 max} by 1.91-2.03 mL/(kg·min), handgrip strength by 0.98-1.56 kg, and sit-and-reach by 0.14-0.32 cm. Increasing LPA result ed in BMI increases of 0.11-0.12 units, handgrip strength increases of 0.65 kg, and sit-and-reach increases of 0.21 cm. Increasing SLP was associated with BMI reduction of 0.04 units and waist circumference reduction of 0.09 cm.CONCLUSION MPA had the most significant effect on improving BMI, body fat percentage, and waist circumference, while VPA was more effective in enhancing cardiorespiratory fitness, muscular strength, and flexibility. SLP had a modest positive effect on BMI and waist circumference but was less impactful than MPA and VPA. SB and LPA were generally unfavorable for health-related physical fitness.