Energy Cost During the 6-Minute Walk Test and Its Relationship to Real-World Walking After Stroke: A Correlational, Cross-Sectional Pilot Study

Background. After experiencing stroke, individuals expend more energy walking than people who are healthy. However, among individuals who have experienced stroke, the correlation between the energy cost of walking, as measured by validated tests (such as the 6-minute walk test), and participation in walking, as measured by more sensitive tools (such as an ambulatory activity monitor), remains unknown. Objective. The main objective of this study was to determine whether the energy cost of walking is correlated with participation in walking. Design. This study was a correlational, cross-sectional pilot study. Methods. Data from 23 participants who had experienced chronic stroke were analyzed. On the first day, data on oxygen uptake were collected using a portable metabolic system while participants walked during the 6-minute walk test. Then, the ambulatory activity monitor was placed on the participants' nonparetic ankle and removed 9 days later. The energy cost of walking was calculated by dividing the mean oxygen uptake recorded during the steady state by the walking speed. Results. The energy cost of walking was correlated with the following: the number of steps (Spearman rank correlation coefficient [rs] = -0.59); the percentage of time spent in inactivity (rs = 0.48), low cadence (rs = 0.67), medium cadence (rs = -0.56), high cadence (rs = -0.65), and the percentages of steps taken at low cadence (rs = 0.65) and high cadence (rs = -0.64). Limitations. Individuals who were physically inactive, convenience sampling, and a small sample size were used in this study. Conclusions. Higher energy costs of walking were associated with fewer steps per day and lower cadence in real-world walking in individuals who had experienced stroke.