Fig. 1.

Walking patterns of a healthy subject and COPD patients based on the NSPS. The healthy subject (A: a 66-year-old woman) and the COPD patient with rest (B: a 64-year-old man) and the COPD patient without rest (C: a 68-year-old man) walked 504.5 m, 224.5 m and 356.5 m, respectively. Although the healthy could walk without stopping, the patient (B) rested for 83 s. When the walking pace is slower, the NSPS is smaller, and becomes zero if the patient stops walking. COPD, chronic obstructive pulmonary disease; NSPS, number of steps per second.