Figure 1.

Scatter plot of walking speed (m/s) and intensity (METs) values observed during overground walking at a self-selected preferred walking pace for the whole sample and separated by age group. The shapes of the data points represent the classification of bouts as true positives (open circles), true negatives (open triangles), false positives (filled circles), and false negatives (filled triangles). The dotted line represents absolutely-defined moderate intensity (≥ 3 METs). The dashed line in each subplot represents the identified age-specific moderate-intensity walking speed (1.28, 1.25 and 1.23 m/s for healthy young, middle-aged and older adults, respectively).