Intensity and physiological responses to the 6-minute walk test in middle-aged and older adults: a comparison with cardiopulmonary exercise testing

The 6-minute walk test (6MWT) is a simple field test that is widely used in clinical settings to assess functional exercise capacity. However, studies with healthy subjects are scarce. We hypothesized that the 6MWT might be useful to assess exercise capacity in healthy subjects. The purpose of this study was to evaluate 6MWT intensity in middle-aged and older adults, as well as to develop a simple equation to predict oxygen uptake ( V ˙ O 2) from the 6-min walk distance (6MWD). Eighty-six participants, 40 men and 46 women, 40-74 years of age and with a mean body mass index of 28±6 kg/m2, performed the 6MWT according to American Thoracic Society guidelines. Physiological responses were evaluated during the 6MWT using a K4b2 Cosmed telemetry gas analyzer. On a different occasion, the subjects performed ramp protocol cardiopulmonary exercise testing (CPET) on a treadmill. Peak V ˙ O 2 in the 6MWT corresponded to 78±13% of the peak V ˙ O 2 during CPET, and the maximum heart rate corresponded to 80±23% of that obtained in CPET. Peak V ˙ O 2 in CPET was adequately predicted by the 6MWD by a linear regression equation: V ˙ O 2 mL·min-1·kg-1 = -2.863 + (0.0563×6MWDm) (R2=0.76). The 6MWT represents a moderate-to-high intensity activity in middle-aged and older adults and proved to be useful for predicting cardiorespiratory fitness in the present study. Our results suggest that the 6MWT may also be useful in asymptomatic individuals, and its use in walk-based conditioning programs should be encouraged.

6分钟步行试验（6-minute walk test, 6MWT）是一项简便的现场测试，被广泛应用于临床场景以评估功能性运动能力。然而，针对健康受试者的相关研究仍较为匮乏。本研究假设6MWT可用于评估健康受试者的运动能力，旨在探究中老年人群的6MWT强度特征，并建立基于6分钟步行距离（6-min walk distance, 6MWD）预测摄氧量（V̇O₂）的简易公式。本研究共纳入86名受试者，其中男性40名、女性46名，年龄介于40~74岁，平均身体质量指数为28±6 kg/m²，所有受试者均按照美国胸科学会指南完成6MWT。试验过程中，采用K4b2 Cosmed遥测气体分析仪监测受试者的生理反应。在另一试验场次中，受试者于跑台上完成递增方案心肺运动试验（cardiopulmonary exercise testing, CPET）。6MWT中的峰值摄氧量约为CPET中峰值摄氧量的78±13%，受试者的最大心率约为CPET测得最大心率的80±23%。通过线性回归方程，可由6MWD较好地预测CPET中的峰值摄氧量，公式为：V̇O₂ mL·min⁻¹·kg⁻¹ = -2.863 + (0.0563×6MWDm)，决定系数R²=0.76。本研究结果显示，6MWT在中老年人群中属于中高强度运动，且可有效预测心肺适能。此外，本研究结果提示6MWT或可应用于无症状个体，应鼓励其在步行训练项目中推广使用。