Screening for physical inactivity among adults: the value of distance walked in the six-minute walk test. A cross-sectional diagnostic study

ABSTRACT: CONTEXT AND OBJECTIVES: Accelerometry provides objective measurement of physical activity levels, but is unfeasible in clinical practice. Thus, we aimed to identify physical fitness tests capable of predicting physical inactivity among adults. DESIGN AND SETTING: Diagnostic test study developed at a university laboratory and a diagnostic clinic. METHODS: 188 asymptomatic subjects underwent assessment of physical activity levels through accelerometry, ergospirometry on treadmill, body composition from bioelectrical impedance, isokinetic muscle function, postural balance on a force platform and six-minute walk test. We conducted descriptive analysis and multiple logistic regression including age, sex, oxygen uptake, body fat, center of pressure, quadriceps peak torque, distance covered in six-minute walk test and steps/day in the model, as predictors of physical inactivity. We also determined sensitivity (S), specificity (Sp) and area under the curve of the main predictors by means of receiver operating characteristic curves. RESULTS: The prevalence of physical inactivity was 14%. The mean number of steps/day (≤ 5357) was the best predictor of physical inactivity (S = 99%; Sp = 82%). The best physical fitness test was a distance in the six-minute walk test and ≤ 96% of predicted values (S = 70%; Sp = 80%). Body fat > 25% was also significant (S = 83%; Sp = 51%). After logistic regression, steps/day and distance in the six-minute walk test remained predictors of physical inactivity. CONCLUSION: The six-minute walk test should be included in epidemiological studies as a simple and cheap tool for screening for physical inactivity.

摘要：
研究背景与目的：加速度计（accelerometry）可客观测量身体活动水平，但在临床实践中难以推广应用。因此本研究旨在筛选可用于预测成年人身体活动不足的体能测试方案。
研究设计与实施场景：本研究为诊断性试验研究，在大学实验室及专科诊断诊所开展。
研究方法：共纳入188名无症状受试者，通过加速度计评估其日常身体活动水平，依次开展跑台心肺运动测试、生物电阻抗法身体成分分析、等速肌肉功能测试、测力台姿势平衡测试以及6分钟步行试验（six-minute walk test）。本研究采用描述性统计分析与多元logistic回归分析，将年龄、性别、摄氧量、体脂率、压力中心、股四头肌峰力矩、6分钟步行试验步行距离及每日步数纳入预测模型，用于评估身体活动不足的发生风险。同时通过受试者工作特征（receiver operating characteristic，ROC）曲线计算各主要预测因子的灵敏度（S）、特异度（Sp）及曲线下面积。
研究结果：本研究队列中身体活动不足的患病率为14%。每日平均步数（≤5357步）是预测身体活动不足的最优指标（灵敏度99%，特异度82%）。最佳体能测试指标为6分钟步行试验步行距离≤预测值的96%（灵敏度70%，特异度80%）。体脂率＞25%同样具备显著预测价值（灵敏度83%，特异度51%）。经多元logistic回归校正后，每日步数与6分钟步行试验步行距离仍为身体活动不足的独立预测因子。
结论：6分钟步行试验可作为一种简便易行、成本低廉的筛查工具，纳入流行病学研究用于人群身体活动不足的筛查工作。