Six-minute walk test: a tool for predicting maximal aerobic power (VO₂ max) in healthy adults

Background: The 6-min walk test (6MWT) is cost-effective and well-documented field test for assessing functional exercise capacity and response to medical interventions in diverse patient groups, and predicting cardiorespiratory fitness among healthy people.

Objective: Assessments of cardiorespiratory fitness in terms of maximal aerobic power (VO₂ max) have great potential in public health monitoring to predict future health, early retirement and ability to independent living. This study aimed to develop a prediction model for VO₂ max based on 6MWT results among healthy adults.

Design: The study comprised of pilot and validation studies. In validation study, seventy-five 19- to 75-year-old adults (39 men, 36 women) were equipped with portable gas analyser and heart rate monitor. Participants performed 6MWT on a 15-m indoor track and maximal graded exercise test (GXT) on a treadmill. We evaluated performance of the developed prediction model among 1583 Finnish adults.

Results: Participant's mean walking distance was 652 m (SD ± 74). Their mean VO₂ max in GXT and O₂ uptake at the end of the 6MWT were 34·4 ml kg^-1 min^-1 (SD ± 7·6) and 27·2 ml kg^-1 min^-1 (SD ± 6·5), respectively. For men, the best predictors for VO₂ max were walking distance, age, BMI, heart rate at the end of 6MWT and height, and for women, walking distance, age and weight. The predictors explained 82% and 79% of men's and women's measured VO₂ max with the standard error of estimate of 3·6 ml kg^-1 min^-1 and 3·5 ml kg^-1 min^-1 , respectively.

Conclusion: The 6MWT performed along a 15-m track is a valid field test for predicting VO₂ max of healthy adults with accuracy of about 1MET.